Hi,
Many subsystems and drivers have the need to register CPU hotplug callbacks
from their init routines and also perform initialization for the CPUs that are
already online. But unfortunately there is no race-free way to achieve this
today.
For example, consider this piece of code:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is not safe because there is a possibility of an ABBA deadlock involving
the cpu_add_remove_lock and the cpu_hotplug.lock.
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
Other combinations of callback registration also don't work correctly.
Examples:
register_cpu_notifier(&foobar_cpu_notifier);
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
put_online_cpus();
This can lead to double initialization if a hotplug operation occurs after
registering the notifier and before invoking get_online_cpus().
On the other hand, the following piece of code can miss hotplug events
altogether:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
put_online_cpus();
^
| Race window; Can miss hotplug events here
v
register_cpu_notifier(&foobar_cpu_notifier);
To solve these issues and provide a race-free method to register CPU hotplug
callbacks, this patchset introduces new variants of the callback registration
APIs that don't hold the cpu_add_remove_lock, and exports the
cpu_add_remove_lock via 2 new APIs cpu_notifier_register_begin/done() for use
by various subsystems. With this in place, the following code snippet will
register a hotplug callback as well as initialize already online CPUs without
any race conditions.
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
In this patchset, patch 1 adds lockdep annotations to catch the above mentioned
deadlock scenario. Patch 2 introduces the new APIs and infrastructure necessary
for race-free callback registration. The remaining patches perform tree-wide
conversions (to use this model).
This patchset has been hosted in the below git tree. It applies cleanly on
v3.14-rc1.
git://github.com/srivatsabhat/linux.git cpuhp-registration-fixes-v2
Gautham R. Shenoy (1):
CPU hotplug: Add lockdep annotations to get/put_online_cpus()
Srivatsa S. Bhat (51):
CPU hotplug: Provide lockless versions of callback registration functions
Doc/cpu-hotplug: Specify race-free way to register CPU hotplug callbacks
CPU hotplug, perf: Fix CPU hotplug callback registration
ia64, salinfo: Fix hotplug callback registration
ia64, palinfo: Fix CPU hotplug callback registration
ia64, topology: Fix CPU hotplug callback registration
ia64, err-inject: Fix CPU hotplug callback registration
arm, hw-breakpoint: Fix CPU hotplug callback registration
arm, kvm: Fix CPU hotplug callback registration
s390, cacheinfo: Fix CPU hotplug callback registration
s390, smp: Fix CPU hotplug callback registration
sparc, sysfs: Fix CPU hotplug callback registration
powerpc, sysfs: Fix CPU hotplug callback registration
x86, msr: Fix CPU hotplug callback registration
x86, cpuid: Fix CPU hotplug callback registration
x86, vsyscall: Fix CPU hotplug callback registration
x86, intel, uncore: Fix CPU hotplug callback registration
x86, mce: Fix CPU hotplug callback registration
x86, therm_throt.c: Fix CPU hotplug callback registration
x86, therm_throt.c: Remove unused therm_cpu_lock
x86, amd, ibs: Fix CPU hotplug callback registration
x86, intel, cacheinfo: Fix CPU hotplug callback registration
x86, intel, rapl: Fix CPU hotplug callback registration
x86, amd, uncore: Fix CPU hotplug callback registration
x86, hpet: Fix CPU hotplug callback registration
x86, pci, amd-bus: Fix CPU hotplug callback registration
x86, oprofile, nmi: Fix CPU hotplug callback registration
x86, kvm: Fix CPU hotplug callback registration
arm64, hw_breakpoint.c: Fix CPU hotplug callback registration
arm64, debug-monitors: Fix CPU hotplug callback registration
powercap, intel-rapl: Fix CPU hotplug callback registration
scsi, bnx2i: Fix CPU hotplug callback registration
scsi, bnx2fc: Fix CPU hotplug callback registration
scsi, fcoe: Fix CPU hotplug callback registration
zsmalloc: Fix CPU hotplug callback registration
acpi-cpufreq: Fix CPU hotplug callback registration
drivers/base/topology.c: Fix CPU hotplug callback registration
clocksource, dummy-timer: Fix CPU hotplug callback registration
intel-idle: Fix CPU hotplug callback registration
oprofile, nmi-timer: Fix CPU hotplug callback registration
octeon, watchdog: Fix CPU hotplug callback registration
thermal, x86-pkg-temp: Fix CPU hotplug callback registration
hwmon, coretemp: Fix CPU hotplug callback registration
hwmon, via-cputemp: Fix CPU hotplug callback registration
xen, balloon: Fix CPU hotplug callback registration
trace, ring-buffer: Fix CPU hotplug callback registration
profile: Fix CPU hotplug callback registration
mm, vmstat: Fix CPU hotplug callback registration
mm, zswap: Fix CPU hotplug callback registration
net/core/flow.c: Fix CPU hotplug callback registration
net/iucv/iucv.c: Fix CPU hotplug callback registration
Documentation/cpu-hotplug.txt | 45 +++++++++
arch/arm/kernel/hw_breakpoint.c | 8 +-
arch/arm/kvm/arm.c | 7 +
arch/arm64/kernel/debug-monitors.c | 6 +
arch/arm64/kernel/hw_breakpoint.c | 7 +
arch/ia64/kernel/err_inject.c | 15 +++
arch/ia64/kernel/palinfo.c | 6 +
arch/ia64/kernel/salinfo.c | 6 +
arch/ia64/kernel/topology.c | 6 +
arch/powerpc/kernel/sysfs.c | 8 +-
arch/s390/kernel/cache.c | 5 +
arch/s390/kernel/smp.c | 13 ++-
arch/sparc/kernel/sysfs.c | 6 +
arch/x86/kernel/cpu/intel_cacheinfo.c | 13 ++-
arch/x86/kernel/cpu/mcheck/mce.c | 8 +-
arch/x86/kernel/cpu/mcheck/therm_throt.c | 18 +---
arch/x86/kernel/cpu/perf_event_amd_ibs.c | 6 +
arch/x86/kernel/cpu/perf_event_amd_uncore.c | 7 +
arch/x86/kernel/cpu/perf_event_intel_rapl.c | 9 +-
arch/x86/kernel/cpu/perf_event_intel_uncore.c | 6 +
arch/x86/kernel/cpuid.c | 15 ++-
arch/x86/kernel/hpet.c | 4 +
arch/x86/kernel/msr.c | 16 ++-
arch/x86/kernel/vsyscall_64.c | 6 +
arch/x86/kvm/x86.c | 7 +
arch/x86/oprofile/nmi_int.c | 15 +++
arch/x86/pci/amd_bus.c | 5 +
drivers/base/topology.c | 12 ++
drivers/clocksource/dummy_timer.c | 11 ++
drivers/cpufreq/acpi-cpufreq.c | 7 +
drivers/hwmon/coretemp.c | 14 +--
drivers/hwmon/via-cputemp.c | 14 +--
drivers/idle/intel_idle.c | 12 ++
drivers/oprofile/nmi_timer_int.c | 23 +++--
drivers/powercap/intel_rapl.c | 10 ++
drivers/scsi/bnx2fc/bnx2fc_fcoe.c | 12 ++
drivers/scsi/bnx2i/bnx2i_init.c | 12 ++
drivers/scsi/fcoe/fcoe.c | 15 +++
drivers/thermal/x86_pkg_temp_thermal.c | 14 +--
drivers/watchdog/octeon-wdt-main.c | 11 ++
drivers/xen/balloon.c | 35 +++++--
include/linux/cpu.h | 47 ++++++++++
include/linux/perf_event.h | 16 +++
kernel/cpu.c | 38 +++++++-
kernel/profile.c | 20 +++-
kernel/trace/ring_buffer.c | 19 ++--
mm/vmstat.c | 6 +
mm/zsmalloc.c | 17 +++-
mm/zswap.c | 8 +-
net/core/flow.c | 8 +-
net/iucv/iucv.c | 121 ++++++++++++-------------
51 files changed, 549 insertions(+), 226 deletions(-)
Regards,
Srivatsa S. Bhat
IBM Linux Technology Center
From: Gautham R. Shenoy <[email protected]>
Add lockdep annotations for get/put_online_cpus() and
cpu_hotplug_begin()/cpu_hotplug_end().
Cc: Ingo Molnar <[email protected]>
Reviewed-by: Oleg Nesterov <[email protected]>
Signed-off-by: Gautham R. Shenoy <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
kernel/cpu.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index deff2e6..33caf5e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -19,6 +19,7 @@
#include <linux/mutex.h>
#include <linux/gfp.h>
#include <linux/suspend.h>
+#include <linux/lockdep.h>
#include "smpboot.h"
@@ -57,17 +58,30 @@ static struct {
* an ongoing cpu hotplug operation.
*/
int refcount;
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ struct lockdep_map dep_map;
+#endif
} cpu_hotplug = {
.active_writer = NULL,
.lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
.refcount = 0,
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
+ .dep_map = {.name = "cpu_hotplug.lock" },
+#endif
};
+/* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
+#define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
+#define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
+#define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
+
void get_online_cpus(void)
{
might_sleep();
if (cpu_hotplug.active_writer == current)
return;
+ cpuhp_lock_acquire_read();
mutex_lock(&cpu_hotplug.lock);
cpu_hotplug.refcount++;
mutex_unlock(&cpu_hotplug.lock);
@@ -87,6 +101,7 @@ void put_online_cpus(void)
if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
wake_up_process(cpu_hotplug.active_writer);
mutex_unlock(&cpu_hotplug.lock);
+ cpuhp_lock_release();
}
EXPORT_SYMBOL_GPL(put_online_cpus);
@@ -117,6 +132,7 @@ void cpu_hotplug_begin(void)
{
cpu_hotplug.active_writer = current;
+ cpuhp_lock_acquire();
for (;;) {
mutex_lock(&cpu_hotplug.lock);
if (likely(!cpu_hotplug.refcount))
@@ -131,6 +147,7 @@ void cpu_hotplug_done(void)
{
cpu_hotplug.active_writer = NULL;
mutex_unlock(&cpu_hotplug.lock);
+ cpuhp_lock_release();
}
/*
The following method of CPU hotplug callback registration is not safe
due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
and the cpu_hotplug.lock.
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
The deadlock is shown below:
CPU 0 CPU 1
----- -----
Acquire cpu_hotplug.lock
[via get_online_cpus()]
CPU online/offline operation
takes cpu_add_remove_lock
[via cpu_maps_update_begin()]
Try to acquire
cpu_add_remove_lock
[via register_cpu_notifier()]
CPU online/offline operation
tries to acquire cpu_hotplug.lock
[via cpu_hotplug_begin()]
*** DEADLOCK! ***
The problem here is that callback registration takes the locks in one order
whereas the CPU hotplug operations take the same locks in the opposite order.
To avoid this issue and to provide a race-free method to register CPU hotplug
callbacks (along with initialization of already online CPUs), introduce new
variants of the callback registration APIs that simply register the callbacks
without holding the cpu_add_remove_lock during the registration. That way,
we can avoid the ABBA scenario. However, we will need to hold the
cpu_add_remove_lock throughout the entire critical section, to protect updates
to the callback/notifier chain.
This can be achieved by writing the callback registration code as follows:
cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
for_each_online_cpu(cpu)
init_cpu(cpu);
/* This doesn't take the cpu_add_remove_lock */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
notifiers, and hence get_online_cpus() cannot provide the necessary
synchronization to protect the callback/notifier chains against concurrent
reads and writes. On the other hand, since the cpu_add_remove_lock protects
the entire hotplug operation (including CPU_POST_DEAD), we can use
cpu_maps_update_begin/done() to guarantee proper synchronization.
Also, since cpu_maps_update_begin/done() is like a super-set of
get/put_online_cpus(), the former naturally protects the critical sections
from concurrent hotplug operations.
Since the names cpu_maps_update_begin/done() don't make much sense in CPU
hotplug callback registration scenarios, we'll introduce new APIs named
cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
In summary, introduce the lockless variants of un/register_cpu_notifier() and
also export the cpu_notifier_register_begin/done() APIs for use by modules.
This way, we provide a race-free way to register hotplug callbacks as well as
perform initialization for the CPUs that are already online.
Cc: Thomas Gleixner <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Ingo Molnar <[email protected]>
Acked-by: Oleg Nesterov <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
include/linux/cpu.h | 47 +++++++++++++++++++++++++++++++++++++++++++++++
kernel/cpu.c | 21 +++++++++++++++++++--
2 files changed, 66 insertions(+), 2 deletions(-)
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 03e235ad..488d6eb 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -122,26 +122,46 @@ enum {
{ .notifier_call = fn, .priority = pri }; \
register_cpu_notifier(&fn##_nb); \
}
+
+#define __cpu_notifier(fn, pri) { \
+ static struct notifier_block fn##_nb = \
+ { .notifier_call = fn, .priority = pri }; \
+ __register_cpu_notifier(&fn##_nb); \
+}
#else /* #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
+#define __cpu_notifier(fn, pri) do { (void)(fn); } while (0)
#endif /* #else #if defined(CONFIG_HOTPLUG_CPU) || !defined(MODULE) */
+
#ifdef CONFIG_HOTPLUG_CPU
extern int register_cpu_notifier(struct notifier_block *nb);
+extern int __register_cpu_notifier(struct notifier_block *nb);
extern void unregister_cpu_notifier(struct notifier_block *nb);
+extern void __unregister_cpu_notifier(struct notifier_block *nb);
#else
#ifndef MODULE
extern int register_cpu_notifier(struct notifier_block *nb);
+extern int __register_cpu_notifier(struct notifier_block *nb);
#else
static inline int register_cpu_notifier(struct notifier_block *nb)
{
return 0;
}
+
+static inline int __register_cpu_notifier(struct notifier_block *nb)
+{
+ return 0;
+}
#endif
static inline void unregister_cpu_notifier(struct notifier_block *nb)
{
}
+
+static inline void __unregister_cpu_notifier(struct notifier_block *nb)
+{
+}
#endif
int cpu_up(unsigned int cpu);
@@ -149,19 +169,32 @@ void notify_cpu_starting(unsigned int cpu);
extern void cpu_maps_update_begin(void);
extern void cpu_maps_update_done(void);
+#define cpu_notifier_register_begin cpu_maps_update_begin
+#define cpu_notifier_register_done cpu_maps_update_done
+
#else /* CONFIG_SMP */
#define cpu_notifier(fn, pri) do { (void)(fn); } while (0)
+#define __cpu_notifier(fn, pri) do { (void)(fn); } while (0)
static inline int register_cpu_notifier(struct notifier_block *nb)
{
return 0;
}
+static inline int __register_cpu_notifier(struct notifier_block *nb)
+{
+ return 0;
+}
+
static inline void unregister_cpu_notifier(struct notifier_block *nb)
{
}
+static inline void __unregister_cpu_notifier(struct notifier_block *nb)
+{
+}
+
static inline void cpu_maps_update_begin(void)
{
}
@@ -170,6 +203,14 @@ static inline void cpu_maps_update_done(void)
{
}
+static inline void cpu_notifier_register_begin(void)
+{
+}
+
+static inline void cpu_notifier_register_done(void)
+{
+}
+
#endif /* CONFIG_SMP */
extern struct bus_type cpu_subsys;
@@ -183,8 +224,11 @@ extern void put_online_cpus(void);
extern void cpu_hotplug_disable(void);
extern void cpu_hotplug_enable(void);
#define hotcpu_notifier(fn, pri) cpu_notifier(fn, pri)
+#define __hotcpu_notifier(fn, pri) __cpu_notifier(fn, pri)
#define register_hotcpu_notifier(nb) register_cpu_notifier(nb)
+#define __register_hotcpu_notifier(nb) __register_cpu_notifier(nb)
#define unregister_hotcpu_notifier(nb) unregister_cpu_notifier(nb)
+#define __unregister_hotcpu_notifier(nb) __unregister_cpu_notifier(nb)
void clear_tasks_mm_cpumask(int cpu);
int cpu_down(unsigned int cpu);
@@ -197,9 +241,12 @@ static inline void cpu_hotplug_done(void) {}
#define cpu_hotplug_disable() do { } while (0)
#define cpu_hotplug_enable() do { } while (0)
#define hotcpu_notifier(fn, pri) do { (void)(fn); } while (0)
+#define __hotcpu_notifier(fn, pri) do { (void)(fn); } while (0)
/* These aren't inline functions due to a GCC bug. */
#define register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
+#define __register_hotcpu_notifier(nb) ({ (void)(nb); 0; })
#define unregister_hotcpu_notifier(nb) ({ (void)(nb); })
+#define __unregister_hotcpu_notifier(nb) ({ (void)(nb); })
#endif /* CONFIG_HOTPLUG_CPU */
#ifdef CONFIG_PM_SLEEP_SMP
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 33caf5e..a9e710e 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -28,18 +28,23 @@
static DEFINE_MUTEX(cpu_add_remove_lock);
/*
- * The following two API's must be used when attempting
- * to serialize the updates to cpu_online_mask, cpu_present_mask.
+ * The following two APIs (cpu_maps_update_begin/done) must be used when
+ * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
+ * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
+ * hotplug callback (un)registration performed using __register_cpu_notifier()
+ * or __unregister_cpu_notifier().
*/
void cpu_maps_update_begin(void)
{
mutex_lock(&cpu_add_remove_lock);
}
+EXPORT_SYMBOL(cpu_notifier_register_begin);
void cpu_maps_update_done(void)
{
mutex_unlock(&cpu_add_remove_lock);
}
+EXPORT_SYMBOL(cpu_notifier_register_done);
static RAW_NOTIFIER_HEAD(cpu_chain);
@@ -183,6 +188,11 @@ int __ref register_cpu_notifier(struct notifier_block *nb)
return ret;
}
+int __ref __register_cpu_notifier(struct notifier_block *nb)
+{
+ return raw_notifier_chain_register(&cpu_chain, nb);
+}
+
static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
int *nr_calls)
{
@@ -206,6 +216,7 @@ static void cpu_notify_nofail(unsigned long val, void *v)
BUG_ON(cpu_notify(val, v));
}
EXPORT_SYMBOL(register_cpu_notifier);
+EXPORT_SYMBOL(__register_cpu_notifier);
void __ref unregister_cpu_notifier(struct notifier_block *nb)
{
@@ -215,6 +226,12 @@ void __ref unregister_cpu_notifier(struct notifier_block *nb)
}
EXPORT_SYMBOL(unregister_cpu_notifier);
+void __ref __unregister_cpu_notifier(struct notifier_block *nb)
+{
+ raw_notifier_chain_unregister(&cpu_chain, nb);
+}
+EXPORT_SYMBOL(__unregister_cpu_notifier);
+
/**
* clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
* @cpu: a CPU id
Recommend the usage of the new CPU hotplug callback registration APIs
(__register_cpu_notifier() etc), when subsystems need to also perform
initialization for already online CPUs. Provide examples of correct
and race-free ways of achieving this, and point out the kinds of code
that are error-prone.
Cc: Rob Landley <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
Documentation/cpu-hotplug.txt | 45 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
diff --git a/Documentation/cpu-hotplug.txt b/Documentation/cpu-hotplug.txt
index be675d2..a0b005d 100644
--- a/Documentation/cpu-hotplug.txt
+++ b/Documentation/cpu-hotplug.txt
@@ -312,12 +312,57 @@ things will happen if a notifier in path sent a BAD notify code.
Q: I don't see my action being called for all CPUs already up and running?
A: Yes, CPU notifiers are called only when new CPUs are on-lined or offlined.
If you need to perform some action for each cpu already in the system, then
+ do this:
for_each_online_cpu(i) {
foobar_cpu_callback(&foobar_cpu_notifier, CPU_UP_PREPARE, i);
foobar_cpu_callback(&foobar_cpu_notifier, CPU_ONLINE, i);
}
+ However, if you want to register a hotplug callback, as well as perform
+ some initialization for CPUs that are already online, then do this:
+
+ Version 1: (Correct)
+ ---------
+
+ cpu_notifier_register_begin();
+
+ for_each_online_cpu(i) {
+ foobar_cpu_callback(&foobar_cpu_notifier,
+ CPU_UP_PREPARE, i);
+ foobar_cpu_callback(&foobar_cpu_notifier,
+ CPU_ONLINE, i);
+ }
+
+ /* Note the use of the double underscored version of the API */
+ __register_cpu_notifier(&foobar_cpu_notifier);
+
+ cpu_notifier_register_done();
+
+ Note that the following code is *NOT* the right way to achieve this,
+ because it is prone to an ABBA deadlock between the cpu_add_remove_lock
+ and the cpu_hotplug.lock.
+
+ Version 2: (Wrong!)
+ ---------
+
+ get_online_cpus();
+
+ for_each_online_cpu(i) {
+ foobar_cpu_callback(&foobar_cpu_notifier,
+ CPU_UP_PREPARE, i);
+ foobar_cpu_callback(&foobar_cpu_notifier,
+ CPU_ONLINE, i);
+ }
+
+ register_cpu_notifier(&foobar_cpu_notifier);
+
+ put_online_cpus();
+
+ So always use the first version shown above when you want to register
+ callbacks as well as initialize the already online CPUs.
+
+
Q: If i would like to develop cpu hotplug support for a new architecture,
what do i need at a minimum?
A: The following are what is required for CPU hotplug infrastructure to work
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the palinfo code in ia64 by using this latter form of callback
registration.
Cc: Tony Luck <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/ia64/kernel/palinfo.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/palinfo.c b/arch/ia64/kernel/palinfo.c
index ab33328..c39c3cd 100644
--- a/arch/ia64/kernel/palinfo.c
+++ b/arch/ia64/kernel/palinfo.c
@@ -996,13 +996,17 @@ palinfo_init(void)
if (!palinfo_dir)
return -ENOMEM;
+ cpu_notifier_register_begin();
+
/* Create palinfo dirs in /proc for all online cpus */
for_each_online_cpu(i) {
create_palinfo_proc_entries(i);
}
/* Register for future delivery via notify registration */
- register_hotcpu_notifier(&palinfo_cpu_notifier);
+ __register_hotcpu_notifier(&palinfo_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the topology code in ia64 by using this latter form of callback
registration.
Cc: Tony Luck <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/ia64/kernel/topology.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/topology.c b/arch/ia64/kernel/topology.c
index ca69a5a..f295f9a 100644
--- a/arch/ia64/kernel/topology.c
+++ b/arch/ia64/kernel/topology.c
@@ -454,12 +454,16 @@ static int __init cache_sysfs_init(void)
{
int i;
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
struct device *sys_dev = get_cpu_device((unsigned int)i);
cache_add_dev(sys_dev);
}
- register_hotcpu_notifier(&cache_cpu_notifier);
+ __register_hotcpu_notifier(&cache_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the error injection code in ia64 by using this latter form of callback
registration.
Cc: Tony Luck <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/ia64/kernel/err_inject.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/ia64/kernel/err_inject.c b/arch/ia64/kernel/err_inject.c
index f59c0b8..0c161ed 100644
--- a/arch/ia64/kernel/err_inject.c
+++ b/arch/ia64/kernel/err_inject.c
@@ -269,12 +269,17 @@ err_inject_init(void)
#ifdef ERR_INJ_DEBUG
printk(KERN_INFO "Enter error injection driver.\n");
#endif
+
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
err_inject_cpu_callback(&err_inject_cpu_notifier, CPU_ONLINE,
(void *)(long)i);
}
- register_hotcpu_notifier(&err_inject_cpu_notifier);
+ __register_hotcpu_notifier(&err_inject_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
@@ -288,11 +293,17 @@ err_inject_exit(void)
#ifdef ERR_INJ_DEBUG
printk(KERN_INFO "Exit error injection driver.\n");
#endif
+
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
sys_dev = get_cpu_device(i);
sysfs_remove_group(&sys_dev->kobj, &err_inject_attr_group);
}
- unregister_hotcpu_notifier(&err_inject_cpu_notifier);
+
+ __unregister_hotcpu_notifier(&err_inject_cpu_notifier);
+
+ cpu_notifier_register_done();
}
module_init(err_inject_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hw-breakpoint code in arm by using this latter form of callback
registration.
Cc: Russell King <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Acked-by: Will Deacon <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/arm/kernel/hw_breakpoint.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 3d44660..3702de8 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -1072,6 +1072,8 @@ static int __init arch_hw_breakpoint_init(void)
core_num_brps = get_num_brps();
core_num_wrps = get_num_wrps();
+ cpu_notifier_register_begin();
+
/*
* We need to tread carefully here because DBGSWENABLE may be
* driven low on this core and there isn't an architected way to
@@ -1088,6 +1090,7 @@ static int __init arch_hw_breakpoint_init(void)
if (!cpumask_empty(&debug_err_mask)) {
core_num_brps = 0;
core_num_wrps = 0;
+ cpu_notifier_register_done();
return 0;
}
@@ -1107,7 +1110,10 @@ static int __init arch_hw_breakpoint_init(void)
TRAP_HWBKPT, "breakpoint debug exception");
/* Register hotplug and PM notifiers. */
- register_cpu_notifier(&dbg_reset_nb);
+ __register_cpu_notifier(&dbg_reset_nb);
+
+ cpu_notifier_register_done();
+
pm_init();
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the perf subsystem's hotplug notifier by using this latter form of
callback registration.
Also provide a bare-bones version of perf_cpu_notifier() that doesn't
invoke the notifiers for the already online CPUs. This would be useful
for subsystems that need to perform a different set of initialization
for the already online CPUs, or don't need the initialization altogether.
Cc: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
include/linux/perf_event.h | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index e56b07f..3356abc 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -835,6 +835,8 @@ do { \
{ .notifier_call = fn, .priority = CPU_PRI_PERF }; \
unsigned long cpu = smp_processor_id(); \
unsigned long flags; \
+ \
+ cpu_notifier_register_begin(); \
fn(&fn##_nb, (unsigned long)CPU_UP_PREPARE, \
(void *)(unsigned long)cpu); \
local_irq_save(flags); \
@@ -843,9 +845,21 @@ do { \
local_irq_restore(flags); \
fn(&fn##_nb, (unsigned long)CPU_ONLINE, \
(void *)(unsigned long)cpu); \
- register_cpu_notifier(&fn##_nb); \
+ __register_cpu_notifier(&fn##_nb); \
+ cpu_notifier_register_done(); \
} while (0)
+/*
+ * Bare-bones version of perf_cpu_notifier(), which doesn't invoke the
+ * callback for already online CPUs.
+ */
+#define __perf_cpu_notifier(fn) \
+do { \
+ static struct notifier_block fn##_nb = \
+ { .notifier_call = fn, .priority = CPU_PRI_PERF }; \
+ \
+ __register_cpu_notifier(&fn##_nb); \
+} while (0)
struct perf_pmu_events_attr {
struct device_attribute attr;
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the cacheinfo code in s390 by using this latter form of callback
registration.
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/s390/kernel/cache.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/s390/kernel/cache.c b/arch/s390/kernel/cache.c
index 3a414c0..c0b03c2 100644
--- a/arch/s390/kernel/cache.c
+++ b/arch/s390/kernel/cache.c
@@ -378,9 +378,12 @@ static int __init cache_init(void)
if (!test_facility(34))
return 0;
cache_build_info();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
cache_add_cpu(cpu);
- hotcpu_notifier(cache_hotplug, 0);
+ __hotcpu_notifier(cache_hotplug, 0);
+ cpu_notifier_register_done();
return 0;
}
device_initcall(cache_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the smp code in s390 by using this latter form of callback registration.
Cc: Martin Schwidefsky <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/s390/kernel/smp.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index a7125b6..e10be35 100644
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -1057,19 +1057,24 @@ static DEVICE_ATTR(rescan, 0200, NULL, rescan_store);
static int __init s390_smp_init(void)
{
- int cpu, rc;
+ int cpu, rc = 0;
- hotcpu_notifier(smp_cpu_notify, 0);
#ifdef CONFIG_HOTPLUG_CPU
rc = device_create_file(cpu_subsys.dev_root, &dev_attr_rescan);
if (rc)
return rc;
#endif
+ cpu_notifier_register_begin();
for_each_present_cpu(cpu) {
rc = smp_add_present_cpu(cpu);
if (rc)
- return rc;
+ goto out;
}
- return 0;
+
+ __hotcpu_notifier(smp_cpu_notify, 0);
+
+out:
+ cpu_notifier_register_done();
+ return rc;
}
subsys_initcall(s390_smp_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the sysfs code in sparc by using this latter form of callback
registration.
Cc: "David S. Miller" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/sparc/kernel/sysfs.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/sparc/kernel/sysfs.c b/arch/sparc/kernel/sysfs.c
index c21c673..a364000 100644
--- a/arch/sparc/kernel/sysfs.c
+++ b/arch/sparc/kernel/sysfs.c
@@ -300,7 +300,7 @@ static int __init topology_init(void)
check_mmu_stats();
- register_cpu_notifier(&sysfs_cpu_nb);
+ cpu_notifier_register_begin();
for_each_possible_cpu(cpu) {
struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -310,6 +310,10 @@ static int __init topology_init(void)
register_cpu_online(cpu);
}
+ __register_cpu_notifier(&sysfs_cpu_nb);
+
+ cpu_notifier_register_done();
+
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the sysfs code in powerpc by using this latter form of callback
registration.
Cc: Benjamin Herrenschmidt <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Olof Johansson <[email protected]>
Cc: Wang Dongsheng <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Acked-by: Madhavan Srinivasan <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/powerpc/kernel/sysfs.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index 97e1dc9..d90d4b7 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -975,7 +975,8 @@ static int __init topology_init(void)
int cpu;
register_nodes();
- register_cpu_notifier(&sysfs_cpu_nb);
+
+ cpu_notifier_register_begin();
for_each_possible_cpu(cpu) {
struct cpu *c = &per_cpu(cpu_devices, cpu);
@@ -999,6 +1000,11 @@ static int __init topology_init(void)
if (cpu_online(cpu))
register_cpu_online(cpu);
}
+
+ __register_cpu_notifier(&sysfs_cpu_nb);
+
+ cpu_notifier_register_done();
+
#ifdef CONFIG_PPC64
sysfs_create_dscr_default();
#endif /* CONFIG_PPC64 */
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the msr code in x86 by using this latter form of callback registration.
Cc: "H. Peter Anvin" <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/msr.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 05266b5..c9603ac 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -259,14 +259,15 @@ static int __init msr_init(void)
goto out_chrdev;
}
msr_class->devnode = msr_devnode;
- get_online_cpus();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
err = msr_device_create(i);
if (err != 0)
goto out_class;
}
- register_hotcpu_notifier(&msr_class_cpu_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&msr_class_cpu_notifier);
+ cpu_notifier_register_done();
err = 0;
goto out;
@@ -275,7 +276,7 @@ out_class:
i = 0;
for_each_online_cpu(i)
msr_device_destroy(i);
- put_online_cpus();
+ cpu_notifier_register_done();
class_destroy(msr_class);
out_chrdev:
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
@@ -286,13 +287,14 @@ out:
static void __exit msr_exit(void)
{
int cpu = 0;
- get_online_cpus();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
msr_device_destroy(cpu);
class_destroy(msr_class);
__unregister_chrdev(MSR_MAJOR, 0, NR_CPUS, "cpu/msr");
- unregister_hotcpu_notifier(&msr_class_cpu_notifier);
- put_online_cpus();
+ __unregister_hotcpu_notifier(&msr_class_cpu_notifier);
+ cpu_notifier_register_done();
}
module_init(msr_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the vsyscall code in x86 by using this latter form of callback
registration.
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/vsyscall_64.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c
index 1f96f93..556eaf2 100644
--- a/arch/x86/kernel/vsyscall_64.c
+++ b/arch/x86/kernel/vsyscall_64.c
@@ -393,9 +393,13 @@ static int __init vsyscall_init(void)
{
BUG_ON(VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE));
+ cpu_notifier_register_begin();
+
on_each_cpu(cpu_vsyscall_init, NULL, 1);
/* notifier priority > KVM */
- hotcpu_notifier(cpu_vsyscall_notifier, 30);
+ __hotcpu_notifier(cpu_vsyscall_notifier, 30);
+
+ cpu_notifier_register_done();
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the uncore code in intel-x86 by using this latter form of callback
registration.
Cc: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpu/perf_event_intel_uncore.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index 29c2487..83c3c8b 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -3808,7 +3808,7 @@ static int __init uncore_cpu_init(void)
if (ret)
return ret;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
int i, phys_id = topology_physical_package_id(cpu);
@@ -3827,9 +3827,9 @@ static int __init uncore_cpu_init(void)
}
on_each_cpu(uncore_cpu_setup, NULL, 1);
- register_cpu_notifier(&uncore_cpu_nb);
+ __register_cpu_notifier(&uncore_cpu_nb);
- put_online_cpus();
+ cpu_notifier_register_done();
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the cpuid code in x86 by using this latter form of callback registration.
Cc: "H. Peter Anvin" <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpuid.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/arch/x86/kernel/cpuid.c b/arch/x86/kernel/cpuid.c
index 7d9481c..3225ae6c 100644
--- a/arch/x86/kernel/cpuid.c
+++ b/arch/x86/kernel/cpuid.c
@@ -198,14 +198,15 @@ static int __init cpuid_init(void)
goto out_chrdev;
}
cpuid_class->devnode = cpuid_devnode;
- get_online_cpus();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
err = cpuid_device_create(i);
if (err != 0)
goto out_class;
}
- register_hotcpu_notifier(&cpuid_class_cpu_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&cpuid_class_cpu_notifier);
+ cpu_notifier_register_done();
err = 0;
goto out;
@@ -215,7 +216,7 @@ out_class:
for_each_online_cpu(i) {
cpuid_device_destroy(i);
}
- put_online_cpus();
+ cpu_notifier_register_done();
class_destroy(cpuid_class);
out_chrdev:
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
@@ -227,13 +228,13 @@ static void __exit cpuid_exit(void)
{
int cpu = 0;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
cpuid_device_destroy(cpu);
class_destroy(cpuid_class);
__unregister_chrdev(CPUID_MAJOR, 0, NR_CPUS, "cpu/cpuid");
- unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
- put_online_cpus();
+ __unregister_hotcpu_notifier(&cpuid_class_cpu_notifier);
+ cpu_notifier_register_done();
}
module_init(cpuid_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the thermal throttle code in x86 by using this latter form of callback
registration.
Cc: Tony Luck <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpu/mcheck/therm_throt.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c
index 3eec7de..e05dfa3 100644
--- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
+++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
@@ -319,7 +319,7 @@ static __init int thermal_throttle_init_device(void)
if (!atomic_read(&therm_throt_en))
return 0;
- register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
+ cpu_notifier_register_begin();
#ifdef CONFIG_HOTPLUG_CPU
mutex_lock(&therm_cpu_lock);
@@ -333,6 +333,9 @@ static __init int thermal_throttle_init_device(void)
mutex_unlock(&therm_cpu_lock);
#endif
+ __register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
+ cpu_notifier_register_done();
+
return 0;
}
device_initcall(thermal_throttle_init_device);
After fixing the CPU hotplug callback registration code, the callbacks
invoked for each online CPU, during the initialization phase in
thermal_throttle_init_device(), can no longer race with the actual CPU
hotplug notifier callbacks (in thermal_throttle_cpu_callback). Hence the
therm_cpu_lock is unnecessary now. Remove it.
Cc: Tony Luck <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Suggested-by: Oleg Nesterov <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpu/mcheck/therm_throt.c | 13 -------------
1 file changed, 13 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/therm_throt.c b/arch/x86/kernel/cpu/mcheck/therm_throt.c
index e05dfa3..d921b7e 100644
--- a/arch/x86/kernel/cpu/mcheck/therm_throt.c
+++ b/arch/x86/kernel/cpu/mcheck/therm_throt.c
@@ -271,9 +271,6 @@ static void thermal_throttle_remove_dev(struct device *dev)
sysfs_remove_group(&dev->kobj, &thermal_attr_group);
}
-/* Mutex protecting device creation against CPU hotplug: */
-static DEFINE_MUTEX(therm_cpu_lock);
-
/* Get notified when a cpu comes on/off. Be hotplug friendly. */
static int
thermal_throttle_cpu_callback(struct notifier_block *nfb,
@@ -289,18 +286,14 @@ thermal_throttle_cpu_callback(struct notifier_block *nfb,
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- mutex_lock(&therm_cpu_lock);
err = thermal_throttle_add_dev(dev, cpu);
- mutex_unlock(&therm_cpu_lock);
WARN_ON(err);
break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
case CPU_DEAD:
case CPU_DEAD_FROZEN:
- mutex_lock(&therm_cpu_lock);
thermal_throttle_remove_dev(dev);
- mutex_unlock(&therm_cpu_lock);
break;
}
return notifier_from_errno(err);
@@ -321,17 +314,11 @@ static __init int thermal_throttle_init_device(void)
cpu_notifier_register_begin();
-#ifdef CONFIG_HOTPLUG_CPU
- mutex_lock(&therm_cpu_lock);
-#endif
/* connect live CPUs to sysfs */
for_each_online_cpu(cpu) {
err = thermal_throttle_add_dev(get_cpu_device(cpu), cpu);
WARN_ON(err);
}
-#ifdef CONFIG_HOTPLUG_CPU
- mutex_unlock(&therm_cpu_lock);
-#endif
__register_hotcpu_notifier(&thermal_throttle_cpu_notifier);
cpu_notifier_register_done();
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the amd-ibs code in x86 by using this latter form of callback
registration.
Cc: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpu/perf_event_amd_ibs.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
index 4b8e4d3..4c36bbe 100644
--- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c
+++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
@@ -926,13 +926,13 @@ static __init int amd_ibs_init(void)
goto out;
perf_ibs_pm_init();
- get_online_cpus();
+ cpu_notifier_register_begin();
ibs_caps = caps;
/* make ibs_caps visible to other cpus: */
smp_mb();
- perf_cpu_notifier(perf_ibs_cpu_notifier);
smp_call_function(setup_APIC_ibs, NULL, 1);
- put_online_cpus();
+ __perf_cpu_notifier(perf_ibs_cpu_notifier);
+ cpu_notifier_register_done();
ret = perf_event_ibs_init();
out:
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the intel cacheinfo code in x86 by using this latter form of callback
registration.
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: Borislav Petkov <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpu/intel_cacheinfo.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/arch/x86/kernel/cpu/intel_cacheinfo.c b/arch/x86/kernel/cpu/intel_cacheinfo.c
index 0641113..a952e9c 100644
--- a/arch/x86/kernel/cpu/intel_cacheinfo.c
+++ b/arch/x86/kernel/cpu/intel_cacheinfo.c
@@ -1225,21 +1225,24 @@ static struct notifier_block cacheinfo_cpu_notifier = {
static int __init cache_sysfs_init(void)
{
- int i;
+ int i, err = 0;
if (num_cache_leaves == 0)
return 0;
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
- int err;
struct device *dev = get_cpu_device(i);
err = cache_add_dev(dev);
if (err)
- return err;
+ goto out;
}
- register_hotcpu_notifier(&cacheinfo_cpu_notifier);
- return 0;
+ __register_hotcpu_notifier(&cacheinfo_cpu_notifier);
+
+out:
+ cpu_notifier_register_done();
+ return err;
}
device_initcall(cache_sysfs_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the amd-uncore code in x86 by using this latter form of callback
registration.
Cc: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpu/perf_event_amd_uncore.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_amd_uncore.c b/arch/x86/kernel/cpu/perf_event_amd_uncore.c
index 754291a..3bbdf4c 100644
--- a/arch/x86/kernel/cpu/perf_event_amd_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_amd_uncore.c
@@ -531,15 +531,16 @@ static int __init amd_uncore_init(void)
if (ret)
return -ENODEV;
- get_online_cpus();
+ cpu_notifier_register_begin();
+
/* init cpus already online before registering for hotplug notifier */
for_each_online_cpu(cpu) {
amd_uncore_cpu_up_prepare(cpu);
smp_call_function_single(cpu, init_cpu_already_online, NULL, 1);
}
- register_cpu_notifier(&amd_uncore_cpu_notifier_block);
- put_online_cpus();
+ __register_cpu_notifier(&amd_uncore_cpu_notifier_block);
+ cpu_notifier_register_done();
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hpet code in x86 by using this latter form of callback registration.
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/hpet.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index da85a8e..d89382b 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -943,12 +943,14 @@ static __init int hpet_late_init(void)
if (boot_cpu_has(X86_FEATURE_ARAT))
return 0;
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
hpet_cpuhp_notify(NULL, CPU_ONLINE, (void *)(long)cpu);
}
/* This notifier should be called after workqueue is ready */
- hotcpu_notifier(hpet_cpuhp_notify, -20);
+ __hotcpu_notifier(hpet_cpuhp_notify, -20);
+ cpu_notifier_register_done();
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the oprofile code in x86 by using this latter form of callback
registration. But retain the calls to get/put_online_cpus(), since they are
used in other places as well, to protect the variables 'nmi_enabled' and
'ctr_running'. Strictly speaking, this is not necessary since
cpu_notifier_register_begin/done() provide a stronger synchronization
with CPU hotplug than get/put_online_cpus(). However, let's retain the
calls to get/put_online_cpus() to be consistent with the other call-sites.
By nesting get/put_online_cpus() *inside* cpu_notifier_register_begin/done(),
we avoid the ABBA deadlock possibility mentioned above.
Cc: Robert Richter <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/oprofile/nmi_int.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/arch/x86/oprofile/nmi_int.c b/arch/x86/oprofile/nmi_int.c
index 6890d84..379e8bd 100644
--- a/arch/x86/oprofile/nmi_int.c
+++ b/arch/x86/oprofile/nmi_int.c
@@ -494,14 +494,19 @@ static int nmi_setup(void)
if (err)
goto fail;
+ cpu_notifier_register_begin();
+
+ /* Use get/put_online_cpus() to protect 'nmi_enabled' */
get_online_cpus();
- register_cpu_notifier(&oprofile_cpu_nb);
nmi_enabled = 1;
/* make nmi_enabled visible to the nmi handler: */
smp_mb();
on_each_cpu(nmi_cpu_setup, NULL, 1);
+ __register_cpu_notifier(&oprofile_cpu_nb);
put_online_cpus();
+ cpu_notifier_register_done();
+
return 0;
fail:
free_msrs();
@@ -512,12 +517,18 @@ static void nmi_shutdown(void)
{
struct op_msrs *msrs;
+ cpu_notifier_register_begin();
+
+ /* Use get/put_online_cpus() to protect 'nmi_enabled' & 'ctr_running' */
get_online_cpus();
- unregister_cpu_notifier(&oprofile_cpu_nb);
on_each_cpu(nmi_cpu_shutdown, NULL, 1);
nmi_enabled = 0;
ctr_running = 0;
+ __unregister_cpu_notifier(&oprofile_cpu_nb);
put_online_cpus();
+
+ cpu_notifier_register_done();
+
/* make variables visible to the nmi handler: */
smp_mb();
unregister_nmi_handler(NMI_LOCAL, "oprofile");
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the amd-bus code in x86 by using this latter form of callback
registration.
Cc: Bjorn Helgaas <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/pci/amd_bus.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/pci/amd_bus.c b/arch/x86/pci/amd_bus.c
index a48be98..f05cbf0 100644
--- a/arch/x86/pci/amd_bus.c
+++ b/arch/x86/pci/amd_bus.c
@@ -380,10 +380,13 @@ static int __init pci_io_ecs_init(void)
if (early_pci_allowed())
pci_enable_pci_io_ecs();
- register_cpu_notifier(&amd_cpu_notifier);
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
amd_cpu_notify(&amd_cpu_notifier, (unsigned long)CPU_ONLINE,
(void *)(long)cpu);
+ __register_cpu_notifier(&amd_cpu_notifier);
+ cpu_notifier_register_done();
+
pci_probe |= PCI_HAS_IO_ECS;
return 0;
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the kvm code in x86 by using this latter form of callback registration.
Cc: Gleb Natapov <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kvm/x86.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 39c28f09..0166923 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -5365,7 +5365,8 @@ static void kvm_timer_init(void)
int cpu;
max_tsc_khz = tsc_khz;
- register_hotcpu_notifier(&kvmclock_cpu_notifier_block);
+
+ cpu_notifier_register_begin();
if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
#ifdef CONFIG_CPU_FREQ
struct cpufreq_policy policy;
@@ -5382,6 +5383,10 @@ static void kvm_timer_init(void)
pr_debug("kvm: max_tsc_khz = %ld\n", max_tsc_khz);
for_each_online_cpu(cpu)
smp_call_function_single(cpu, tsc_khz_changed, NULL, 1);
+
+ __register_hotcpu_notifier(&kvmclock_cpu_notifier_block);
+ cpu_notifier_register_done();
+
}
static DEFINE_PER_CPU(struct kvm_vcpu *, current_vcpu);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hw-breakpoint code in arm64 by using this latter form of callback
registration.
Cc: Catalin Marinas <[email protected]>
Cc: Lorenzo Pieralisi <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Acked-by: Will Deacon <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/arm64/kernel/hw_breakpoint.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/hw_breakpoint.c b/arch/arm64/kernel/hw_breakpoint.c
index f17f581..bee7897 100644
--- a/arch/arm64/kernel/hw_breakpoint.c
+++ b/arch/arm64/kernel/hw_breakpoint.c
@@ -913,6 +913,8 @@ static int __init arch_hw_breakpoint_init(void)
pr_info("found %d breakpoint and %d watchpoint registers.\n",
core_num_brps, core_num_wrps);
+ cpu_notifier_register_begin();
+
/*
* Reset the breakpoint resources. We assume that a halting
* debugger will leave the world in a nice state for us.
@@ -927,7 +929,10 @@ static int __init arch_hw_breakpoint_init(void)
TRAP_HWBKPT, "hw-watchpoint handler");
/* Register hotplug notifier. */
- register_cpu_notifier(&hw_breakpoint_reset_nb);
+ __register_cpu_notifier(&hw_breakpoint_reset_nb);
+
+ cpu_notifier_register_done();
+
/* Register cpu_suspend hw breakpoint restore hook */
cpu_suspend_set_dbg_restorer(hw_breakpoint_reset);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the debug-monitors code in arm64 by using this latter form of callback
registration.
Cc: Catalin Marinas <[email protected]>
Cc: Russell King <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Acked-by: Will Deacon <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/arm64/kernel/debug-monitors.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c
index 636ba8b..c985531 100644
--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -155,12 +155,16 @@ static struct notifier_block os_lock_nb = {
static int debug_monitors_init(void)
{
+ cpu_notifier_register_begin();
+
/* Clear the OS lock. */
smp_call_function(clear_os_lock, NULL, 1);
clear_os_lock(NULL);
/* Register hotplug handler. */
- register_cpu_notifier(&os_lock_nb);
+ __register_cpu_notifier(&os_lock_nb);
+
+ cpu_notifier_register_done();
return 0;
}
postcore_initcall(debug_monitors_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the intel-rapl code in the powercap driver by using this latter form
of callback registration. But retain the calls to get/put_online_cpus(),
since they also protect the function rapl_cleanup_data(). By nesting
get/put_online_cpus() *inside* cpu_notifier_register_begin/done(), we avoid
the ABBA deadlock possibility mentioned above.
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Jacob Pan <[email protected]>
Cc: Srinivas Pandruvada <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/powercap/intel_rapl.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/powercap/intel_rapl.c b/drivers/powercap/intel_rapl.c
index 3c67683..d6c74c1 100644
--- a/drivers/powercap/intel_rapl.c
+++ b/drivers/powercap/intel_rapl.c
@@ -1369,6 +1369,9 @@ static int __init rapl_init(void)
return -ENODEV;
}
+
+ cpu_notifier_register_begin();
+
/* prevent CPU hotplug during detection */
get_online_cpus();
ret = rapl_detect_topology();
@@ -1380,20 +1383,23 @@ static int __init rapl_init(void)
ret = -ENODEV;
goto done;
}
- register_hotcpu_notifier(&rapl_cpu_notifier);
+ __register_hotcpu_notifier(&rapl_cpu_notifier);
done:
put_online_cpus();
+ cpu_notifier_register_done();
return ret;
}
static void __exit rapl_exit(void)
{
+ cpu_notifier_register_begin();
get_online_cpus();
- unregister_hotcpu_notifier(&rapl_cpu_notifier);
+ __unregister_hotcpu_notifier(&rapl_cpu_notifier);
rapl_unregister_powercap();
rapl_cleanup_data();
put_online_cpus();
+ cpu_notifier_register_done();
}
module_init(rapl_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the bnx2i code in scsi by using this latter form of callback registration.
Cc: Eddie Wai <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/scsi/bnx2i/bnx2i_init.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/bnx2i/bnx2i_init.c b/drivers/scsi/bnx2i/bnx2i_init.c
index 34c294b..80c03b4 100644
--- a/drivers/scsi/bnx2i/bnx2i_init.c
+++ b/drivers/scsi/bnx2i/bnx2i_init.c
@@ -537,11 +537,15 @@ static int __init bnx2i_mod_init(void)
p->iothread = NULL;
}
+ cpu_notifier_register_begin();
+
for_each_online_cpu(cpu)
bnx2i_percpu_thread_create(cpu);
/* Initialize per CPU interrupt thread */
- register_hotcpu_notifier(&bnx2i_cpu_notifier);
+ __register_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
@@ -581,11 +585,15 @@ static void __exit bnx2i_mod_exit(void)
}
mutex_unlock(&bnx2i_dev_lock);
- unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
bnx2i_percpu_thread_destroy(cpu);
+ __unregister_hotcpu_notifier(&bnx2i_cpu_notifier);
+
+ cpu_notifier_register_done();
+
iscsi_unregister_transport(&bnx2i_iscsi_transport);
cnic_unregister_driver(CNIC_ULP_ISCSI);
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the bnx2fc code in scsi by using this latter form of callback
registration.
Cc: Eddie Wai <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/scsi/bnx2fc/bnx2fc_fcoe.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
index 9b94850..c4ec235 100644
--- a/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
+++ b/drivers/scsi/bnx2fc/bnx2fc_fcoe.c
@@ -2586,12 +2586,16 @@ static int __init bnx2fc_mod_init(void)
spin_lock_init(&p->fp_work_lock);
}
+ cpu_notifier_register_begin();
+
for_each_online_cpu(cpu) {
bnx2fc_percpu_thread_create(cpu);
}
/* Initialize per CPU interrupt thread */
- register_hotcpu_notifier(&bnx2fc_cpu_notifier);
+ __register_hotcpu_notifier(&bnx2fc_cpu_notifier);
+
+ cpu_notifier_register_done();
cnic_register_driver(CNIC_ULP_FCOE, &bnx2fc_cnic_cb);
@@ -2656,13 +2660,17 @@ static void __exit bnx2fc_mod_exit(void)
if (l2_thread)
kthread_stop(l2_thread);
- unregister_hotcpu_notifier(&bnx2fc_cpu_notifier);
+ cpu_notifier_register_begin();
/* Destroy per cpu threads */
for_each_online_cpu(cpu) {
bnx2fc_percpu_thread_destroy(cpu);
}
+ __unregister_hotcpu_notifier(&bnx2fc_cpu_notifier);
+
+ cpu_notifier_register_done();
+
destroy_workqueue(bnx2fc_wq);
/*
* detach from scsi transport
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the fcoe code in scsi by using this latter form of callback registration.
Cc: Robert Love <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/scsi/fcoe/fcoe.c | 15 +++++++++++++--
1 file changed, 13 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/fcoe/fcoe.c b/drivers/scsi/fcoe/fcoe.c
index f317000..d5e105b 100644
--- a/drivers/scsi/fcoe/fcoe.c
+++ b/drivers/scsi/fcoe/fcoe.c
@@ -2633,14 +2633,18 @@ static int __init fcoe_init(void)
skb_queue_head_init(&p->fcoe_rx_list);
}
+ cpu_notifier_register_begin();
+
for_each_online_cpu(cpu)
fcoe_percpu_thread_create(cpu);
/* Initialize per CPU interrupt thread */
- rc = register_hotcpu_notifier(&fcoe_cpu_notifier);
+ rc = __register_hotcpu_notifier(&fcoe_cpu_notifier);
if (rc)
goto out_free;
+ cpu_notifier_register_done();
+
/* Setup link change notification */
fcoe_dev_setup();
@@ -2655,6 +2659,9 @@ out_free:
for_each_online_cpu(cpu) {
fcoe_percpu_thread_destroy(cpu);
}
+
+ cpu_notifier_register_done();
+
mutex_unlock(&fcoe_config_mutex);
destroy_workqueue(fcoe_wq);
return rc;
@@ -2687,11 +2694,15 @@ static void __exit fcoe_exit(void)
}
rtnl_unlock();
- unregister_hotcpu_notifier(&fcoe_cpu_notifier);
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
fcoe_percpu_thread_destroy(cpu);
+ __unregister_hotcpu_notifier(&fcoe_cpu_notifier);
+
+ cpu_notifier_register_done();
+
mutex_unlock(&fcoe_config_mutex);
/*
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the zsmalloc code by using this latter form of callback registration.
Cc: Minchan Kim <[email protected]>
Cc: Nitin Gupta <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
mm/zsmalloc.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index c03ca5e..36b4591 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -814,21 +814,32 @@ static void zs_exit(void)
{
int cpu;
+ cpu_notifier_register_begin();
+
for_each_online_cpu(cpu)
zs_cpu_notifier(NULL, CPU_DEAD, (void *)(long)cpu);
- unregister_cpu_notifier(&zs_cpu_nb);
+ __unregister_cpu_notifier(&zs_cpu_nb);
+
+ cpu_notifier_register_done();
}
static int zs_init(void)
{
int cpu, ret;
- register_cpu_notifier(&zs_cpu_nb);
+ cpu_notifier_register_begin();
+
+ __register_cpu_notifier(&zs_cpu_nb);
for_each_online_cpu(cpu) {
ret = zs_cpu_notifier(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
- if (notifier_to_errno(ret))
+ if (notifier_to_errno(ret)) {
+ cpu_notifier_register_done();
goto fail;
+ }
}
+
+ cpu_notifier_register_done();
+
return 0;
fail:
zs_exit();
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the acpi-cpufreq code by using this latter form of callback registration.
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: [email protected]
Acked-by: Viresh Kumar <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/cpufreq/acpi-cpufreq.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 18448a7..245ae078e 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -907,15 +907,16 @@ static void __init acpi_cpufreq_boost_init(void)
acpi_cpufreq_driver.boost_supported = true;
acpi_cpufreq_driver.boost_enabled = boost_state(0);
- get_online_cpus();
+
+ cpu_notifier_register_begin();
/* Force all MSRs to the same value */
boost_set_msrs(acpi_cpufreq_driver.boost_enabled,
cpu_online_mask);
- register_cpu_notifier(&boost_nb);
+ __register_cpu_notifier(&boost_nb);
- put_online_cpus();
+ cpu_notifier_register_done();
}
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the topology code by using this latter form of callback registration.
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/base/topology.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)
diff --git a/drivers/base/topology.c b/drivers/base/topology.c
index 94ffee3..a738d10 100644
--- a/drivers/base/topology.c
+++ b/drivers/base/topology.c
@@ -161,16 +161,20 @@ static int topology_cpu_callback(struct notifier_block *nfb,
static int topology_sysfs_init(void)
{
int cpu;
- int rc;
+ int rc = 0;
+
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
rc = topology_add_dev(cpu);
if (rc)
- return rc;
+ goto out;
}
- hotcpu_notifier(topology_cpu_callback, 0);
+ __hotcpu_notifier(topology_cpu_callback, 0);
- return 0;
+out:
+ cpu_notifier_register_done();
+ return rc;
}
device_initcall(topology_sysfs_init);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the clocksource dummy-timer code by using this latter form of callback
registration.
Cc: Daniel Lezcano <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/clocksource/dummy_timer.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)
diff --git a/drivers/clocksource/dummy_timer.c b/drivers/clocksource/dummy_timer.c
index b3eb582..ad35725 100644
--- a/drivers/clocksource/dummy_timer.c
+++ b/drivers/clocksource/dummy_timer.c
@@ -56,14 +56,19 @@ static struct notifier_block dummy_timer_cpu_nb = {
static int __init dummy_timer_register(void)
{
- int err = register_cpu_notifier(&dummy_timer_cpu_nb);
+ int err = 0;
+
+ cpu_notifier_register_begin();
+ err = __register_cpu_notifier(&dummy_timer_cpu_nb);
if (err)
- return err;
+ goto out;
/* We won't get a call on the boot CPU, so register immediately */
if (num_possible_cpus() > 1)
dummy_timer_setup();
- return 0;
+out:
+ cpu_notifier_register_done();
+ return err;
}
early_initcall(dummy_timer_register);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the intel-idle code by using this latter form of callback registration.
Cc: Len Brown <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/idle/intel_idle.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/drivers/idle/intel_idle.c b/drivers/idle/intel_idle.c
index 8e1939f..51493ed 100644
--- a/drivers/idle/intel_idle.c
+++ b/drivers/idle/intel_idle.c
@@ -681,14 +681,19 @@ static int __init intel_idle_init(void)
if (intel_idle_cpuidle_devices == NULL)
return -ENOMEM;
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
retval = intel_idle_cpu_init(i);
if (retval) {
+ cpu_notifier_register_done();
cpuidle_unregister_driver(&intel_idle_driver);
return retval;
}
}
- register_cpu_notifier(&cpu_hotplug_notifier);
+ __register_cpu_notifier(&cpu_hotplug_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
@@ -698,10 +703,13 @@ static void __exit intel_idle_exit(void)
intel_idle_cpuidle_devices_uninit();
cpuidle_unregister_driver(&intel_idle_driver);
+ cpu_notifier_register_begin();
if (lapic_timer_reliable_states != LAPIC_TIMER_ALWAYS_RELIABLE)
on_each_cpu(__setup_broadcast_timer, (void *)false, 1);
- unregister_cpu_notifier(&cpu_hotplug_notifier);
+ __unregister_cpu_notifier(&cpu_hotplug_notifier);
+
+ cpu_notifier_register_done();
return;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the nmi-timer code in oprofile by using this latter form of callback
registration.
Cc: Robert Richter <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/oprofile/nmi_timer_int.c | 23 +++++++++++++----------
1 file changed, 13 insertions(+), 10 deletions(-)
diff --git a/drivers/oprofile/nmi_timer_int.c b/drivers/oprofile/nmi_timer_int.c
index 76f1c93..9559829 100644
--- a/drivers/oprofile/nmi_timer_int.c
+++ b/drivers/oprofile/nmi_timer_int.c
@@ -108,8 +108,8 @@ static void nmi_timer_shutdown(void)
struct perf_event *event;
int cpu;
- get_online_cpus();
- unregister_cpu_notifier(&nmi_timer_cpu_nb);
+ cpu_notifier_register_begin();
+ __unregister_cpu_notifier(&nmi_timer_cpu_nb);
for_each_possible_cpu(cpu) {
event = per_cpu(nmi_timer_events, cpu);
if (!event)
@@ -119,7 +119,7 @@ static void nmi_timer_shutdown(void)
perf_event_release_kernel(event);
}
- put_online_cpus();
+ cpu_notifier_register_done();
}
static int nmi_timer_setup(void)
@@ -132,20 +132,23 @@ static int nmi_timer_setup(void)
do_div(period, HZ);
nmi_timer_attr.sample_period = period;
- get_online_cpus();
- err = register_cpu_notifier(&nmi_timer_cpu_nb);
+ cpu_notifier_register_begin();
+ err = __register_cpu_notifier(&nmi_timer_cpu_nb);
if (err)
goto out;
+
/* can't attach events to offline cpus: */
for_each_online_cpu(cpu) {
err = nmi_timer_start_cpu(cpu);
- if (err)
- break;
+ if (err) {
+ cpu_notifier_register_done();
+ nmi_timer_shutdown();
+ return err;
+ }
}
- if (err)
- nmi_timer_shutdown();
+
out:
- put_online_cpus();
+ cpu_notifier_register_done();
return err;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the watchdog code in octeon by using this latter form of callback
registration.
Cc: Wim Van Sebroeck <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/watchdog/octeon-wdt-main.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
diff --git a/drivers/watchdog/octeon-wdt-main.c b/drivers/watchdog/octeon-wdt-main.c
index 4612088..4baf2d7 100644
--- a/drivers/watchdog/octeon-wdt-main.c
+++ b/drivers/watchdog/octeon-wdt-main.c
@@ -708,10 +708,13 @@ static int __init octeon_wdt_init(void)
cpumask_clear(&irq_enabled_cpus);
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
octeon_wdt_setup_interrupt(cpu);
- register_hotcpu_notifier(&octeon_wdt_cpu_notifier);
+ __register_hotcpu_notifier(&octeon_wdt_cpu_notifier);
+ cpu_notifier_register_done();
+
out:
return ret;
}
@@ -725,7 +728,8 @@ static void __exit octeon_wdt_cleanup(void)
misc_deregister(&octeon_wdt_miscdev);
- unregister_hotcpu_notifier(&octeon_wdt_cpu_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&octeon_wdt_cpu_notifier);
for_each_online_cpu(cpu) {
int core = cpu2core(cpu);
@@ -734,6 +738,9 @@ static void __exit octeon_wdt_cleanup(void)
/* Free the interrupt handler */
free_irq(OCTEON_IRQ_WDOG0 + core, octeon_wdt_poke_irq);
}
+
+ cpu_notifier_register_done();
+
/*
* Disable the boot-bus memory, the code it points to is soon
* to go missing.
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the thermal x86-pkg-temp code by using this latter form of callback
registration.
Cc: Zhang Rui <[email protected]>
Cc: Eduardo Valentin <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/thermal/x86_pkg_temp_thermal.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/thermal/x86_pkg_temp_thermal.c b/drivers/thermal/x86_pkg_temp_thermal.c
index 972e1c7..7592048 100644
--- a/drivers/thermal/x86_pkg_temp_thermal.c
+++ b/drivers/thermal/x86_pkg_temp_thermal.c
@@ -589,12 +589,12 @@ static int __init pkg_temp_thermal_init(void)
platform_thermal_package_rate_control =
pkg_temp_thermal_platform_thermal_rate_control;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(i)
if (get_core_online(i))
goto err_ret;
- register_hotcpu_notifier(&pkg_temp_thermal_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&pkg_temp_thermal_notifier);
+ cpu_notifier_register_done();
pkg_temp_debugfs_init(); /* Don't care if fails */
@@ -603,7 +603,7 @@ static int __init pkg_temp_thermal_init(void)
err_ret:
for_each_online_cpu(i)
put_core_offline(i);
- put_online_cpus();
+ cpu_notifier_register_done();
kfree(pkg_work_scheduled);
platform_thermal_package_notify = NULL;
platform_thermal_package_rate_control = NULL;
@@ -616,8 +616,8 @@ static void __exit pkg_temp_thermal_exit(void)
struct phy_dev_entry *phdev, *n;
int i;
- get_online_cpus();
- unregister_hotcpu_notifier(&pkg_temp_thermal_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&pkg_temp_thermal_notifier);
mutex_lock(&phy_dev_list_mutex);
list_for_each_entry_safe(phdev, n, &phy_dev_list, list) {
/* Retore old MSR value for package thermal interrupt */
@@ -635,7 +635,7 @@ static void __exit pkg_temp_thermal_exit(void)
for_each_online_cpu(i)
cancel_delayed_work_sync(
&per_cpu(pkg_temp_thermal_threshold_work, i));
- put_online_cpus();
+ cpu_notifier_register_done();
kfree(pkg_work_scheduled);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hwmon coretemp code by using this latter form of callback
registration.
Cc: Fenghua Yu <[email protected]>
Cc: Jean Delvare <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Acked-by: Guenter Roeck <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/hwmon/coretemp.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index bbb0b0d..746a6ad 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -849,20 +849,20 @@ static int __init coretemp_init(void)
if (err)
goto exit;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(i)
get_core_online(i);
#ifndef CONFIG_HOTPLUG_CPU
if (list_empty(&pdev_list)) {
- put_online_cpus();
+ cpu_notifier_register_done();
err = -ENODEV;
goto exit_driver_unreg;
}
#endif
- register_hotcpu_notifier(&coretemp_cpu_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&coretemp_cpu_notifier);
+ cpu_notifier_register_done();
return 0;
#ifndef CONFIG_HOTPLUG_CPU
@@ -877,8 +877,8 @@ static void __exit coretemp_exit(void)
{
struct pdev_entry *p, *n;
- get_online_cpus();
- unregister_hotcpu_notifier(&coretemp_cpu_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&coretemp_cpu_notifier);
mutex_lock(&pdev_list_mutex);
list_for_each_entry_safe(p, n, &pdev_list, list) {
platform_device_unregister(p->pdev);
@@ -886,7 +886,7 @@ static void __exit coretemp_exit(void)
kfree(p);
}
mutex_unlock(&pdev_list_mutex);
- put_online_cpus();
+ cpu_notifier_register_done();
platform_driver_unregister(&coretemp_driver);
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the hwmon via-cputemp code by using this latter form of callback
registration.
Cc: Jean Delvare <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Acked-by: Guenter Roeck <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/hwmon/via-cputemp.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/hwmon/via-cputemp.c b/drivers/hwmon/via-cputemp.c
index 38944e9..8df43c5 100644
--- a/drivers/hwmon/via-cputemp.c
+++ b/drivers/hwmon/via-cputemp.c
@@ -319,7 +319,7 @@ static int __init via_cputemp_init(void)
if (err)
goto exit;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
struct cpuinfo_x86 *c = &cpu_data(i);
@@ -339,14 +339,14 @@ static int __init via_cputemp_init(void)
#ifndef CONFIG_HOTPLUG_CPU
if (list_empty(&pdev_list)) {
- put_online_cpus();
+ cpu_notifier_register_done();
err = -ENODEV;
goto exit_driver_unreg;
}
#endif
- register_hotcpu_notifier(&via_cputemp_cpu_notifier);
- put_online_cpus();
+ __register_hotcpu_notifier(&via_cputemp_cpu_notifier);
+ cpu_notifier_register_done();
return 0;
#ifndef CONFIG_HOTPLUG_CPU
@@ -361,8 +361,8 @@ static void __exit via_cputemp_exit(void)
{
struct pdev_entry *p, *n;
- get_online_cpus();
- unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&via_cputemp_cpu_notifier);
mutex_lock(&pdev_list_mutex);
list_for_each_entry_safe(p, n, &pdev_list, list) {
platform_device_unregister(p->pdev);
@@ -370,7 +370,7 @@ static void __exit via_cputemp_exit(void)
kfree(p);
}
mutex_unlock(&pdev_list_mutex);
- put_online_cpus();
+ cpu_notifier_register_done();
platform_driver_unregister(&via_cputemp_driver);
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Interestingly, the balloon code in xen can actually prevent double
initialization and hence can use the following simplified form of callback
registration:
register_cpu_notifier(&foobar_cpu_notifier);
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
put_online_cpus();
A hotplug operation that occurs between registering the notifier and calling
get_online_cpus(), won't disrupt anything, because the code takes care to
perform the memory allocations only once.
So reorganize the balloon code in xen this way to fix the deadlock with
callback registration.
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: David Vrabel <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/xen/balloon.c | 35 +++++++++++++++++++++++------------
1 file changed, 23 insertions(+), 12 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 37d06ea..afe1a3f 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -592,19 +592,29 @@ static void __init balloon_add_region(unsigned long start_pfn,
}
}
+static int alloc_balloon_scratch_page(int cpu)
+{
+ if (per_cpu(balloon_scratch_page, cpu) != NULL)
+ return 0;
+
+ per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
+ if (per_cpu(balloon_scratch_page, cpu) == NULL) {
+ pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+
static int balloon_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
int cpu = (long)hcpu;
switch (action) {
case CPU_UP_PREPARE:
- if (per_cpu(balloon_scratch_page, cpu) != NULL)
- break;
- per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
- if (per_cpu(balloon_scratch_page, cpu) == NULL) {
- pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ if (alloc_balloon_scratch_page(cpu))
return NOTIFY_BAD;
- }
break;
default:
break;
@@ -624,15 +634,16 @@ static int __init balloon_init(void)
return -ENODEV;
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
- for_each_online_cpu(cpu)
- {
- per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
- if (per_cpu(balloon_scratch_page, cpu) == NULL) {
- pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ register_cpu_notifier(&balloon_cpu_notifier);
+
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ if (alloc_balloon_scratch_page(cpu)) {
+ put_online_cpus();
return -ENOMEM;
}
}
- register_cpu_notifier(&balloon_cpu_notifier);
+ put_online_cpus();
}
pr_info("Initialising balloon driver\n");
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the tracing ring-buffer code by using this latter form of callback
registration.
Cc: Frederic Weisbecker <[email protected]>
Cc: Ingo Molnar <[email protected]>
Acked-by: Steven Rostedt <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
kernel/trace/ring_buffer.c | 19 +++++++++++--------
1 file changed, 11 insertions(+), 8 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 294b8a2..0893233 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1301,7 +1301,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
* In that off case, we need to allocate for all possible cpus.
*/
#ifdef CONFIG_HOTPLUG_CPU
- get_online_cpus();
+ cpu_notifier_register_begin();
cpumask_copy(buffer->cpumask, cpu_online_mask);
#else
cpumask_copy(buffer->cpumask, cpu_possible_mask);
@@ -1324,10 +1324,10 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
#ifdef CONFIG_HOTPLUG_CPU
buffer->cpu_notify.notifier_call = rb_cpu_notify;
buffer->cpu_notify.priority = 0;
- register_cpu_notifier(&buffer->cpu_notify);
+ __register_cpu_notifier(&buffer->cpu_notify);
+ cpu_notifier_register_done();
#endif
- put_online_cpus();
mutex_init(&buffer->mutex);
return buffer;
@@ -1341,7 +1341,9 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags,
fail_free_cpumask:
free_cpumask_var(buffer->cpumask);
- put_online_cpus();
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_notifier_register_done();
+#endif
fail_free_buffer:
kfree(buffer);
@@ -1358,16 +1360,17 @@ ring_buffer_free(struct ring_buffer *buffer)
{
int cpu;
- get_online_cpus();
-
#ifdef CONFIG_HOTPLUG_CPU
- unregister_cpu_notifier(&buffer->cpu_notify);
+ cpu_notifier_register_begin();
+ __unregister_cpu_notifier(&buffer->cpu_notify);
#endif
for_each_buffer_cpu(buffer, cpu)
rb_free_cpu_buffer(buffer->buffers[cpu]);
- put_online_cpus();
+#ifdef CONFIG_HOTPLUG_CPU
+ cpu_notifier_register_done();
+#endif
kfree(buffer->buffers);
free_cpumask_var(buffer->cpumask);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the profile code by using this latter form of callback registration.
Cc: Al Viro <[email protected]>
Cc: Mauro Carvalho Chehab <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
kernel/profile.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)
diff --git a/kernel/profile.c b/kernel/profile.c
index 6631e1e..4c0cb95 100644
--- a/kernel/profile.c
+++ b/kernel/profile.c
@@ -591,18 +591,28 @@ out_cleanup:
int __ref create_proc_profile(void) /* false positive from hotcpu_notifier */
{
struct proc_dir_entry *entry;
+ int err = 0;
if (!prof_on)
return 0;
- if (create_hash_tables())
- return -ENOMEM;
+
+ cpu_notifier_register_begin();
+
+ if (create_hash_tables()) {
+ err = -ENOMEM;
+ goto out;
+ }
+
entry = proc_create("profile", S_IWUSR | S_IRUGO,
NULL, &proc_profile_operations);
if (!entry)
- return 0;
+ goto out;
proc_set_size(entry, (1 + prof_len) * sizeof(atomic_t));
- hotcpu_notifier(profile_cpu_callback, 0);
- return 0;
+ __hotcpu_notifier(profile_cpu_callback, 0);
+
+out:
+ cpu_notifier_register_done();
+ return err;
}
module_init(create_proc_profile);
#endif /* CONFIG_PROC_FS */
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the vmstat code in the MM subsystem by using this latter form of callback
registration.
Cc: Andrew Morton <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Cody P Schafer <[email protected]>
Cc: Toshi Kani <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Acked-by: Christoph Lameter <[email protected]>
Reviewed-by: Yasuaki Ishimatsu <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
mm/vmstat.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 7249614..12a553e 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -1290,14 +1290,14 @@ static int __init setup_vmstat(void)
#ifdef CONFIG_SMP
int cpu;
- register_cpu_notifier(&vmstat_notifier);
+ cpu_notifier_register_begin();
+ __register_cpu_notifier(&vmstat_notifier);
- get_online_cpus();
for_each_online_cpu(cpu) {
start_cpu_timer(cpu);
node_set_state(cpu_to_node(cpu), N_CPU);
}
- put_online_cpus();
+ cpu_notifier_register_done();
#endif
#ifdef CONFIG_PROC_FS
proc_create("buddyinfo", S_IRUGO, NULL, &fragmentation_file_operations);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the zswap code by using this latter form of callback registration.
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
mm/zswap.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/mm/zswap.c b/mm/zswap.c
index e55bab9..d7337fb 100644
--- a/mm/zswap.c
+++ b/mm/zswap.c
@@ -387,18 +387,18 @@ static int zswap_cpu_init(void)
{
unsigned long cpu;
- get_online_cpus();
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu)
if (__zswap_cpu_notifier(CPU_UP_PREPARE, cpu) != NOTIFY_OK)
goto cleanup;
- register_cpu_notifier(&zswap_cpu_notifier_block);
- put_online_cpus();
+ __register_cpu_notifier(&zswap_cpu_notifier_block);
+ cpu_notifier_register_done();
return 0;
cleanup:
for_each_online_cpu(cpu)
__zswap_cpu_notifier(CPU_UP_CANCELED, cpu);
- put_online_cpus();
+ cpu_notifier_register_done();
return -ENOMEM;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the code in net/core/flow.c by using this latter form of callback
registration.
Cc: Li RongQing <[email protected]>
Cc: Sasha Levin <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Chris Metcalf <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
net/core/flow.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/net/core/flow.c b/net/core/flow.c
index dfa602c..9a2151f 100644
--- a/net/core/flow.c
+++ b/net/core/flow.c
@@ -456,6 +456,8 @@ static int __init flow_cache_init(struct flow_cache *fc)
if (!fc->percpu)
return -ENOMEM;
+ cpu_notifier_register_begin();
+
for_each_online_cpu(i) {
if (flow_cache_cpu_prepare(fc, i))
goto err;
@@ -463,7 +465,9 @@ static int __init flow_cache_init(struct flow_cache *fc)
fc->hotcpu_notifier = (struct notifier_block){
.notifier_call = flow_cache_cpu,
};
- register_hotcpu_notifier(&fc->hotcpu_notifier);
+ __register_hotcpu_notifier(&fc->hotcpu_notifier);
+
+ cpu_notifier_register_done();
setup_timer(&fc->rnd_timer, flow_cache_new_hashrnd,
(unsigned long) fc);
@@ -479,6 +483,8 @@ err:
fcp->hash_table = NULL;
}
+ cpu_notifier_register_done();
+
free_percpu(fc->percpu);
fc->percpu = NULL;
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the code in net/iucv/iucv.c by using this latter form of callback
registration. Also, provide helper functions to perform the common memory
allocations and frees, to condense repetitive code.
Cc: Ursula Braun <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
net/iucv/iucv.c | 121 ++++++++++++++++++++++++++-----------------------------
1 file changed, 57 insertions(+), 64 deletions(-)
diff --git a/net/iucv/iucv.c b/net/iucv/iucv.c
index cd5b8ec..79a0ce9 100644
--- a/net/iucv/iucv.c
+++ b/net/iucv/iucv.c
@@ -621,6 +621,42 @@ static void iucv_disable(void)
put_online_cpus();
}
+static void free_iucv_data(int cpu)
+{
+ kfree(iucv_param_irq[cpu]);
+ iucv_param_irq[cpu] = NULL;
+ kfree(iucv_param[cpu]);
+ iucv_param[cpu] = NULL;
+ kfree(iucv_irq_data[cpu]);
+ iucv_irq_data[cpu] = NULL;
+}
+
+static int alloc_iucv_data(int cpu)
+{
+ /* Note: GFP_DMA used to get memory below 2G */
+ iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
+ GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
+ if (!iucv_irq_data[cpu])
+ goto out_free;
+
+ /* Allocate parameter blocks. */
+ iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
+ GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
+ if (!iucv_param[cpu])
+ goto out_free;
+
+ iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
+ GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
+ if (!iucv_param_irq[cpu])
+ goto out_free;
+
+ return 0;
+
+out_free:
+ free_iucv_data(cpu);
+ return -ENOMEM;
+}
+
static int iucv_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
@@ -630,38 +666,14 @@ static int iucv_cpu_notify(struct notifier_block *self,
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_irq_data[cpu])
- return notifier_from_errno(-ENOMEM);
-
- iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_param[cpu]) {
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
+ if (alloc_iucv_data(cpu))
return notifier_from_errno(-ENOMEM);
- }
- iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_param_irq[cpu]) {
- kfree(iucv_param[cpu]);
- iucv_param[cpu] = NULL;
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
- return notifier_from_errno(-ENOMEM);
- }
break;
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
case CPU_DEAD:
case CPU_DEAD_FROZEN:
- kfree(iucv_param_irq[cpu]);
- iucv_param_irq[cpu] = NULL;
- kfree(iucv_param[cpu]);
- iucv_param[cpu] = NULL;
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
+ free_iucv_data(cpu);
break;
case CPU_ONLINE:
case CPU_ONLINE_FROZEN:
@@ -2025,33 +2037,20 @@ static int __init iucv_init(void)
goto out_int;
}
- for_each_online_cpu(cpu) {
- /* Note: GFP_DMA used to get memory below 2G */
- iucv_irq_data[cpu] = kmalloc_node(sizeof(struct iucv_irq_data),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_irq_data[cpu]) {
- rc = -ENOMEM;
- goto out_free;
- }
+ cpu_notifier_register_begin();
- /* Allocate parameter blocks. */
- iucv_param[cpu] = kmalloc_node(sizeof(union iucv_param),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_param[cpu]) {
- rc = -ENOMEM;
- goto out_free;
- }
- iucv_param_irq[cpu] = kmalloc_node(sizeof(union iucv_param),
- GFP_KERNEL|GFP_DMA, cpu_to_node(cpu));
- if (!iucv_param_irq[cpu]) {
+ for_each_online_cpu(cpu) {
+ if (alloc_iucv_data(cpu)) {
rc = -ENOMEM;
goto out_free;
}
-
}
- rc = register_hotcpu_notifier(&iucv_cpu_notifier);
+ rc = __register_hotcpu_notifier(&iucv_cpu_notifier);
if (rc)
goto out_free;
+
+ cpu_notifier_register_done();
+
rc = register_reboot_notifier(&iucv_reboot_notifier);
if (rc)
goto out_cpu;
@@ -2069,16 +2068,14 @@ static int __init iucv_init(void)
out_reboot:
unregister_reboot_notifier(&iucv_reboot_notifier);
out_cpu:
- unregister_hotcpu_notifier(&iucv_cpu_notifier);
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&iucv_cpu_notifier);
out_free:
- for_each_possible_cpu(cpu) {
- kfree(iucv_param_irq[cpu]);
- iucv_param_irq[cpu] = NULL;
- kfree(iucv_param[cpu]);
- iucv_param[cpu] = NULL;
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
- }
+ for_each_possible_cpu(cpu)
+ free_iucv_data(cpu);
+
+ cpu_notifier_register_done();
+
root_device_unregister(iucv_root);
out_int:
unregister_external_interrupt(0x4000, iucv_external_interrupt);
@@ -2105,15 +2102,11 @@ static void __exit iucv_exit(void)
kfree(p);
spin_unlock_irq(&iucv_queue_lock);
unregister_reboot_notifier(&iucv_reboot_notifier);
- unregister_hotcpu_notifier(&iucv_cpu_notifier);
- for_each_possible_cpu(cpu) {
- kfree(iucv_param_irq[cpu]);
- iucv_param_irq[cpu] = NULL;
- kfree(iucv_param[cpu]);
- iucv_param[cpu] = NULL;
- kfree(iucv_irq_data[cpu]);
- iucv_irq_data[cpu] = NULL;
- }
+ cpu_notifier_register_begin();
+ __unregister_hotcpu_notifier(&iucv_cpu_notifier);
+ for_each_possible_cpu(cpu)
+ free_iucv_data(cpu);
+ cpu_notifier_register_done();
root_device_unregister(iucv_root);
bus_unregister(&iucv_bus);
unregister_external_interrupt(0x4000, iucv_external_interrupt);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the intel rapl code in x86 by using this latter form of callback
registration.
Cc: Peter Zijlstra <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpu/perf_event_intel_rapl.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/cpu/perf_event_intel_rapl.c b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
index 5ad35ad..059218e 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_rapl.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_rapl.c
@@ -646,19 +646,20 @@ static int __init rapl_pmu_init(void)
/* unsupported */
return 0;
}
- get_online_cpus();
+
+ cpu_notifier_register_begin();
for_each_online_cpu(cpu) {
rapl_cpu_prepare(cpu);
rapl_cpu_init(cpu);
}
- perf_cpu_notifier(rapl_cpu_notifier);
+ __perf_cpu_notifier(rapl_cpu_notifier);
ret = perf_pmu_register(&rapl_pmu_class, "power", -1);
if (WARN_ON(ret)) {
pr_info("RAPL PMU detected, registration failed (%d), RAPL PMU disabled\n", ret);
- put_online_cpus();
+ cpu_notifier_register_done();
return -1;
}
@@ -672,7 +673,7 @@ static int __init rapl_pmu_init(void)
hweight32(rapl_cntr_mask),
ktime_to_ms(pmu->timer_interval));
- put_online_cpus();
+ cpu_notifier_register_done();
return 0;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the mce code in x86 by using this latter form of callback registration.
Cc: Tony Luck <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/x86/kernel/cpu/mcheck/mce.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 4d5419b..9b7734b 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -2434,14 +2434,18 @@ static __init int mcheck_init_device(void)
if (err)
return err;
+ cpu_notifier_register_begin();
for_each_online_cpu(i) {
err = mce_device_create(i);
- if (err)
+ if (err) {
+ cpu_notifier_register_done();
return err;
+ }
}
register_syscore_ops(&mce_syscore_ops);
- register_hotcpu_notifier(&mce_cpu_notifier);
+ __register_hotcpu_notifier(&mce_cpu_notifier);
+ cpu_notifier_register_done();
/* register character device /dev/mcelog */
misc_register(&mce_chrdev_device);
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the kvm code in arm by using this latter form of callback registration.
Cc: Christoffer Dall <[email protected]>
Cc: Gleb Natapov <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Russell King <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/arm/kvm/arm.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 1d8248e..147b917 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -1050,21 +1050,26 @@ int kvm_arch_init(void *opaque)
}
}
+ cpu_notifier_register_begin();
+
err = init_hyp_mode();
if (err)
goto out_err;
- err = register_cpu_notifier(&hyp_init_cpu_nb);
+ err = __register_cpu_notifier(&hyp_init_cpu_nb);
if (err) {
kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
goto out_err;
}
+ cpu_notifier_register_done();
+
hyp_cpu_pm_init();
kvm_coproc_table_init();
return 0;
out_err:
+ cpu_notifier_register_done();
return err;
}
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
Instead, the correct and race-free way of performing the callback
registration is:
cpu_notifier_register_begin();
for_each_online_cpu(cpu)
init_cpu(cpu);
/* Note the use of the double underscored version of the API */
__register_cpu_notifier(&foobar_cpu_notifier);
cpu_notifier_register_done();
Fix the salinfo code in ia64 by using this latter form of callback
registration.
Cc: Tony Luck <[email protected]>
Cc: Fenghua Yu <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
arch/ia64/kernel/salinfo.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/arch/ia64/kernel/salinfo.c b/arch/ia64/kernel/salinfo.c
index 960a396..ee9719e 100644
--- a/arch/ia64/kernel/salinfo.c
+++ b/arch/ia64/kernel/salinfo.c
@@ -635,6 +635,8 @@ salinfo_init(void)
(void *)salinfo_entries[i].feature);
}
+ cpu_notifier_register_begin();
+
for (i = 0; i < ARRAY_SIZE(salinfo_log_name); i++) {
data = salinfo_data + i;
data->type = i;
@@ -669,7 +671,9 @@ salinfo_init(void)
salinfo_timer.function = &salinfo_timeout;
add_timer(&salinfo_timer);
- register_hotcpu_notifier(&salinfo_cpu_notifier);
+ __register_hotcpu_notifier(&salinfo_cpu_notifier);
+
+ cpu_notifier_register_done();
return 0;
}
Il 14/02/2014 08:55, Srivatsa S. Bhat ha scritto:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* Note the use of the double underscored version of the API */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> Fix the kvm code in x86 by using this latter form of callback registration.
>
> Cc: Gleb Natapov <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
> ---
>
> arch/x86/kvm/x86.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 39c28f09..0166923 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5365,7 +5365,8 @@ static void kvm_timer_init(void)
> int cpu;
>
> max_tsc_khz = tsc_khz;
> - register_hotcpu_notifier(&kvmclock_cpu_notifier_block);
> +
> + cpu_notifier_register_begin();
> if (!boot_cpu_has(X86_FEATURE_CONSTANT_TSC)) {
> #ifdef CONFIG_CPU_FREQ
> struct cpufreq_policy policy;
> @@ -5382,6 +5383,10 @@ static void kvm_timer_init(void)
> pr_debug("kvm: max_tsc_khz = %ld\n", max_tsc_khz);
> for_each_online_cpu(cpu)
> smp_call_function_single(cpu, tsc_khz_changed, NULL, 1);
> +
> + __register_hotcpu_notifier(&kvmclock_cpu_notifier_block);
> + cpu_notifier_register_done();
> +
> }
>
> static DEFINE_PER_CPU(struct kvm_vcpu *, current_vcpu);
>
Acked-by: Paolo Bonzini <[email protected]>
Il 14/02/2014 08:51, Srivatsa S. Bhat ha scritto:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* Note the use of the double underscored version of the API */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> Fix the kvm code in arm by using this latter form of callback registration.
>
> Cc: Christoffer Dall <[email protected]>
> Cc: Gleb Natapov <[email protected]>
> Cc: Paolo Bonzini <[email protected]>
> Cc: Russell King <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
> ---
>
> arch/arm/kvm/arm.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
> index 1d8248e..147b917 100644
> --- a/arch/arm/kvm/arm.c
> +++ b/arch/arm/kvm/arm.c
> @@ -1050,21 +1050,26 @@ int kvm_arch_init(void *opaque)
> }
> }
>
> + cpu_notifier_register_begin();
> +
> err = init_hyp_mode();
> if (err)
> goto out_err;
>
> - err = register_cpu_notifier(&hyp_init_cpu_nb);
> + err = __register_cpu_notifier(&hyp_init_cpu_nb);
> if (err) {
> kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
> goto out_err;
> }
>
> + cpu_notifier_register_done();
> +
> hyp_cpu_pm_init();
>
> kvm_coproc_table_init();
> return 0;
> out_err:
> + cpu_notifier_register_done();
> return err;
> }
>
>
Acked-by: Paolo Bonzini <[email protected]>
On 02/14/2014 03:00 AM, Srivatsa S. Bhat wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
> Fix the vmstat code in the MM subsystem by using this latter form of callback
> registration.
>
> Cc: Andrew Morton <[email protected]>
> Cc: Rik van Riel <[email protected]>
> Cc: Johannes Weiner <[email protected]>
> Cc: Cody P Schafer <[email protected]>
> Cc: Toshi Kani <[email protected]>
> Cc: Dave Hansen <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Acked-by: Christoph Lameter <[email protected]>
> Reviewed-by: Yasuaki Ishimatsu <[email protected]>
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
Acked-by: Rik van Riel <[email protected]>
--
All rights reversed
On 02/14/2014 02:59 AM, Srivatsa S. Bhat wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Interestingly, the balloon code in xen can actually prevent double
> initialization and hence can use the following simplified form of callback
> registration:
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> put_online_cpus();
>
> A hotplug operation that occurs between registering the notifier and calling
> get_online_cpus(), won't disrupt anything, because the code takes care to
> perform the memory allocations only once.
>
> So reorganize the balloon code in xen this way to fix the deadlock with
> callback registration.
>
> Cc: Konrad Rzeszutek Wilk <[email protected]>
> Cc: Boris Ostrovsky <[email protected]>
> Cc: David Vrabel <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
> ---
>
> drivers/xen/balloon.c | 35 +++++++++++++++++++++++------------
> 1 file changed, 23 insertions(+), 12 deletions(-)
This looks exactly like the earlier version (i.e the notifier is still
kept registered on allocation failure and commit message doesn't exactly
reflect the change).
-boris
>
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 37d06ea..afe1a3f 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -592,19 +592,29 @@ static void __init balloon_add_region(unsigned long start_pfn,
> }
> }
>
> +static int alloc_balloon_scratch_page(int cpu)
> +{
> + if (per_cpu(balloon_scratch_page, cpu) != NULL)
> + return 0;
> +
> + per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
> + if (per_cpu(balloon_scratch_page, cpu) == NULL) {
> + pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
> + return -ENOMEM;
> + }
> +
> + return 0;
> +}
> +
> +
> static int balloon_cpu_notify(struct notifier_block *self,
> unsigned long action, void *hcpu)
> {
> int cpu = (long)hcpu;
> switch (action) {
> case CPU_UP_PREPARE:
> - if (per_cpu(balloon_scratch_page, cpu) != NULL)
> - break;
> - per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
> - if (per_cpu(balloon_scratch_page, cpu) == NULL) {
> - pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
> + if (alloc_balloon_scratch_page(cpu))
> return NOTIFY_BAD;
> - }
> break;
> default:
> break;
> @@ -624,15 +634,16 @@ static int __init balloon_init(void)
> return -ENODEV;
>
> if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> - for_each_online_cpu(cpu)
> - {
> - per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
> - if (per_cpu(balloon_scratch_page, cpu) == NULL) {
> - pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
> + register_cpu_notifier(&balloon_cpu_notifier);
> +
> + get_online_cpus();
> + for_each_online_cpu(cpu) {
> + if (alloc_balloon_scratch_page(cpu)) {
> + put_online_cpus();
> return -ENOMEM;
> }
> }
> - register_cpu_notifier(&balloon_cpu_notifier);
> + put_online_cpus();
> }
>
> pr_info("Initialising balloon driver\n");
>
On 02/14/2014 10:19 PM, Boris Ostrovsky wrote:
> On 02/14/2014 02:59 AM, Srivatsa S. Bhat wrote:
>> Subsystems that want to register CPU hotplug callbacks, as well as
>> perform
>> initialization for the CPUs that are already online, often do it as shown
>> below:
>>
>> get_online_cpus();
>>
>> for_each_online_cpu(cpu)
>> init_cpu(cpu);
>>
>> register_cpu_notifier(&foobar_cpu_notifier);
>>
>> put_online_cpus();
>>
>> This is wrong, since it is prone to ABBA deadlocks involving the
>> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
>> with CPU hotplug operations).
>>
>> Interestingly, the balloon code in xen can actually prevent double
>> initialization and hence can use the following simplified form of
>> callback
>> registration:
>>
>> register_cpu_notifier(&foobar_cpu_notifier);
>>
>> get_online_cpus();
>>
>> for_each_online_cpu(cpu)
>> init_cpu(cpu);
>>
>> put_online_cpus();
>>
>> A hotplug operation that occurs between registering the notifier and
>> calling
>> get_online_cpus(), won't disrupt anything, because the code takes care to
>> perform the memory allocations only once.
>>
>> So reorganize the balloon code in xen this way to fix the deadlock with
>> callback registration.
>>
>> Cc: Konrad Rzeszutek Wilk <[email protected]>
>> Cc: Boris Ostrovsky <[email protected]>
>> Cc: David Vrabel <[email protected]>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: [email protected]
>> Signed-off-by: Srivatsa S. Bhat <[email protected]>
>> ---
>>
>> drivers/xen/balloon.c | 35 +++++++++++++++++++++++------------
>> 1 file changed, 23 insertions(+), 12 deletions(-)
>
>
> This looks exactly like the earlier version (i.e the notifier is still
> kept registered on allocation failure and commit message doesn't exactly
> reflect the change).
>
Sorry, your earlier reply (for some unknown reason) missed the email-threading
and landed elsewhere in my inbox, and hence unfortunately I forgot to take
your suggestions into account while sending out the v2.
I'll send out an updated version of just this patch, as a reply.
Thank you!
Regards,
Srivatsa S. Bhat
>>
>> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
>> index 37d06ea..afe1a3f 100644
>> --- a/drivers/xen/balloon.c
>> +++ b/drivers/xen/balloon.c
>> @@ -592,19 +592,29 @@ static void __init balloon_add_region(unsigned
>> long start_pfn,
>> }
>> }
>> +static int alloc_balloon_scratch_page(int cpu)
>> +{
>> + if (per_cpu(balloon_scratch_page, cpu) != NULL)
>> + return 0;
>> +
>> + per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
>> + if (per_cpu(balloon_scratch_page, cpu) == NULL) {
>> + pr_warn("Failed to allocate balloon_scratch_page for cpu
>> %d\n", cpu);
>> + return -ENOMEM;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +
>> static int balloon_cpu_notify(struct notifier_block *self,
>> unsigned long action, void *hcpu)
>> {
>> int cpu = (long)hcpu;
>> switch (action) {
>> case CPU_UP_PREPARE:
>> - if (per_cpu(balloon_scratch_page, cpu) != NULL)
>> - break;
>> - per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
>> - if (per_cpu(balloon_scratch_page, cpu) == NULL) {
>> - pr_warn("Failed to allocate balloon_scratch_page for cpu
>> %d\n", cpu);
>> + if (alloc_balloon_scratch_page(cpu))
>> return NOTIFY_BAD;
>> - }
>> break;
>> default:
>> break;
>> @@ -624,15 +634,16 @@ static int __init balloon_init(void)
>> return -ENODEV;
>> if (!xen_feature(XENFEAT_auto_translated_physmap)) {
>> - for_each_online_cpu(cpu)
>> - {
>> - per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
>> - if (per_cpu(balloon_scratch_page, cpu) == NULL) {
>> - pr_warn("Failed to allocate balloon_scratch_page for
>> cpu %d\n", cpu);
>> + register_cpu_notifier(&balloon_cpu_notifier);
>> +
>> + get_online_cpus();
>> + for_each_online_cpu(cpu) {
>> + if (alloc_balloon_scratch_page(cpu)) {
>> + put_online_cpus();
>> return -ENOMEM;
>> }
>> }
>> - register_cpu_notifier(&balloon_cpu_notifier);
>> + put_online_cpus();
>> }
>> pr_info("Initialising balloon driver\n");
>>
>
On Fri, Feb 14, 2014 at 12:55 AM, Srivatsa S. Bhat
<[email protected]> wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* Note the use of the double underscored version of the API */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> Fix the amd-bus code in x86 by using this latter form of callback
> registration.
>
> Cc: Bjorn Helgaas <[email protected]>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: "H. Peter Anvin" <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
This looks fine to me.
Acked-by: Bjorn Helgaas <[email protected]>
I think it makes sense for you to merge it along with all your other
similar changes. I don't foresee any conflicts with things in my PCI
tree.
> ---
>
> arch/x86/pci/amd_bus.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/arch/x86/pci/amd_bus.c b/arch/x86/pci/amd_bus.c
> index a48be98..f05cbf0 100644
> --- a/arch/x86/pci/amd_bus.c
> +++ b/arch/x86/pci/amd_bus.c
> @@ -380,10 +380,13 @@ static int __init pci_io_ecs_init(void)
> if (early_pci_allowed())
> pci_enable_pci_io_ecs();
>
> - register_cpu_notifier(&amd_cpu_notifier);
> + cpu_notifier_register_begin();
> for_each_online_cpu(cpu)
> amd_cpu_notify(&amd_cpu_notifier, (unsigned long)CPU_ONLINE,
> (void *)(long)cpu);
> + __register_cpu_notifier(&amd_cpu_notifier);
> + cpu_notifier_register_done();
> +
> pci_probe |= PCI_HAS_IO_ECS;
>
> return 0;
>
On 02/14/2014 11:05 PM, Bjorn Helgaas wrote:
> On Fri, Feb 14, 2014 at 12:55 AM, Srivatsa S. Bhat
> <[email protected]> wrote:
>> Subsystems that want to register CPU hotplug callbacks, as well as perform
>> initialization for the CPUs that are already online, often do it as shown
>> below:
>>
>> get_online_cpus();
>>
>> for_each_online_cpu(cpu)
>> init_cpu(cpu);
>>
>> register_cpu_notifier(&foobar_cpu_notifier);
>>
>> put_online_cpus();
>>
>> This is wrong, since it is prone to ABBA deadlocks involving the
>> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
>> with CPU hotplug operations).
>>
>> Instead, the correct and race-free way of performing the callback
>> registration is:
>>
>> cpu_notifier_register_begin();
>>
>> for_each_online_cpu(cpu)
>> init_cpu(cpu);
>>
>> /* Note the use of the double underscored version of the API */
>> __register_cpu_notifier(&foobar_cpu_notifier);
>>
>> cpu_notifier_register_done();
>>
>>
>> Fix the amd-bus code in x86 by using this latter form of callback
>> registration.
>>
>> Cc: Bjorn Helgaas <[email protected]>
>> Cc: Thomas Gleixner <[email protected]>
>> Cc: Ingo Molnar <[email protected]>
>> Cc: "H. Peter Anvin" <[email protected]>
>> Cc: [email protected]
>> Cc: [email protected]
>> Signed-off-by: Srivatsa S. Bhat <[email protected]>
>
> This looks fine to me.
>
> Acked-by: Bjorn Helgaas <[email protected]>
>
> I think it makes sense for you to merge it along with all your other
> similar changes. I don't foresee any conflicts with things in my PCI
> tree.
>
Great! Thank you!
Regards,
Srivatsa S. Bhat
From: "Srivatsa S. Bhat" <[email protected]>
Date: Fri, 14 Feb 2014 13:22:05 +0530
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
...
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
...
> Fix the sysfs code in sparc by using this latter form of callback
> registration.
>
> Cc: "David S. Miller" <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
Acked-by: David S. Miller <[email protected]>
From: "Srivatsa S. Bhat" <[email protected]>
Date: Fri, 14 Feb 2014 13:30:43 +0530
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
...
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
...
> Fix the code in net/core/flow.c by using this latter form of callback
> registration.
>
> Cc: Li RongQing <[email protected]>
> Cc: Sasha Levin <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Chris Metcalf <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Signed-off-by: David S. Miller <[email protected]>
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
Acked-by: David S. Miller <[email protected]>
From: "Srivatsa S. Bhat" <[email protected]>
Date: Fri, 14 Feb 2014 13:30:58 +0530
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
...
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
...
> Fix the code in net/iucv/iucv.c by using this latter form of callback
> registration. Also, provide helper functions to perform the common memory
> allocations and frees, to condense repetitive code.
>
> Cc: Ursula Braun <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Signed-off-by: David S. Miller <[email protected]>
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
Acked-by: David S. Miller <[email protected]>
On 02/14/2014 10:20 PM, Srivatsa S. Bhat wrote:
> On 02/14/2014 10:19 PM, Boris Ostrovsky wrote:
>> On 02/14/2014 02:59 AM, Srivatsa S. Bhat wrote:
>>> Subsystems that want to register CPU hotplug callbacks, as well as
>>> perform
>>> initialization for the CPUs that are already online, often do it as shown
>>> below:
>>>
[...]
>> This looks exactly like the earlier version (i.e the notifier is still
>> kept registered on allocation failure and commit message doesn't exactly
>> reflect the change).
>>
>
> Sorry, your earlier reply (for some unknown reason) missed the email-threading
> and landed elsewhere in my inbox, and hence unfortunately I forgot to take
> your suggestions into account while sending out the v2.
>
> I'll send out an updated version of just this patch, as a reply.
Here is the updated patch. Please let me know what you think!
----------------------------------------------------------------------------
From: Srivatsa S. Bhat <[email protected]>
Subject: [PATCH] xen, balloon: Fix CPU hotplug callback registration
Subsystems that want to register CPU hotplug callbacks, as well as perform
initialization for the CPUs that are already online, often do it as shown
below:
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
register_cpu_notifier(&foobar_cpu_notifier);
put_online_cpus();
This is wrong, since it is prone to ABBA deadlocks involving the
cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
with CPU hotplug operations).
The xen balloon driver doesn't take get/put_online_cpus() around this code,
but that is also buggy, since it can miss CPU hotplug events in between the
initialization and callback registration:
for_each_online_cpu(cpu)
init_cpu(cpu);
^
| Race window; Can miss CPU hotplug events here.
v
register_cpu_notifier(&foobar_cpu_notifier);
Interestingly, the balloon code in xen can simply be reorganized as shown
below, to have a race-free method to register hotplug callbacks, without even
taking get/put_online_cpus(). This is because the initialization performed for
already online CPUs is exactly the same as that performed for CPUs that come
online later. Moreover, the code has checks in place to avoid double
initialization.
register_cpu_notifier(&foobar_cpu_notifier);
get_online_cpus();
for_each_online_cpu(cpu)
init_cpu(cpu);
put_online_cpus();
A hotplug operation that occurs between registering the notifier and calling
get_online_cpus(), won't disrupt anything, because the code takes care to
perform the memory allocations only once.
So reorganize the balloon code in xen this way to fix the issues with CPU
hotplug callback registration.
Cc: Konrad Rzeszutek Wilk <[email protected]>
Cc: Boris Ostrovsky <[email protected]>
Cc: David Vrabel <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: [email protected]
Signed-off-by: Srivatsa S. Bhat <[email protected]>
---
drivers/xen/balloon.c | 36 ++++++++++++++++++++++++------------
1 file changed, 24 insertions(+), 12 deletions(-)
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 37d06ea..dd79549 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -592,19 +592,29 @@ static void __init balloon_add_region(unsigned long start_pfn,
}
}
+static int alloc_balloon_scratch_page(int cpu)
+{
+ if (per_cpu(balloon_scratch_page, cpu) != NULL)
+ return 0;
+
+ per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
+ if (per_cpu(balloon_scratch_page, cpu) == NULL) {
+ pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+
static int balloon_cpu_notify(struct notifier_block *self,
unsigned long action, void *hcpu)
{
int cpu = (long)hcpu;
switch (action) {
case CPU_UP_PREPARE:
- if (per_cpu(balloon_scratch_page, cpu) != NULL)
- break;
- per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
- if (per_cpu(balloon_scratch_page, cpu) == NULL) {
- pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ if (alloc_balloon_scratch_page(cpu))
return NOTIFY_BAD;
- }
break;
default:
break;
@@ -624,15 +634,17 @@ static int __init balloon_init(void)
return -ENODEV;
if (!xen_feature(XENFEAT_auto_translated_physmap)) {
- for_each_online_cpu(cpu)
- {
- per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
- if (per_cpu(balloon_scratch_page, cpu) == NULL) {
- pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
+ register_cpu_notifier(&balloon_cpu_notifier);
+
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ if (alloc_balloon_scratch_page(cpu)) {
+ put_online_cpus();
+ unregister_cpu_notifier(&balloon_cpu_notifier);
return -ENOMEM;
}
}
- register_cpu_notifier(&balloon_cpu_notifier);
+ put_online_cpus();
}
pr_info("Initialising balloon driver\n");
On Fri, Feb 14, 2014 at 01:27:51PM +0530, Srivatsa S. Bhat wrote:
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> Instead, the correct and race-free way of performing the callback
> registration is:
>
> cpu_notifier_register_begin();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* Note the use of the double underscored version of the API */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_notifier_register_done();
>
>
> Fix the topology code by using this latter form of callback registration.
>
> Cc: Greg Kroah-Hartman <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
On Fri, Feb 14, 2014 at 01:19:23PM +0530, Srivatsa S. Bhat wrote:
> The following method of CPU hotplug callback registration is not safe
> due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
> and the cpu_hotplug.lock.
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> The deadlock is shown below:
>
> CPU 0 CPU 1
> ----- -----
>
> Acquire cpu_hotplug.lock
> [via get_online_cpus()]
>
> CPU online/offline operation
> takes cpu_add_remove_lock
> [via cpu_maps_update_begin()]
>
>
> Try to acquire
> cpu_add_remove_lock
> [via register_cpu_notifier()]
>
>
> CPU online/offline operation
> tries to acquire cpu_hotplug.lock
> [via cpu_hotplug_begin()]
>
>
> *** DEADLOCK! ***
>
> The problem here is that callback registration takes the locks in one order
> whereas the CPU hotplug operations take the same locks in the opposite order.
> To avoid this issue and to provide a race-free method to register CPU hotplug
> callbacks (along with initialization of already online CPUs), introduce new
> variants of the callback registration APIs that simply register the callbacks
> without holding the cpu_add_remove_lock during the registration. That way,
> we can avoid the ABBA scenario. However, we will need to hold the
> cpu_add_remove_lock throughout the entire critical section, to protect updates
> to the callback/notifier chain.
>
> This can be achieved by writing the callback registration code as follows:
>
> cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* This doesn't take the cpu_add_remove_lock */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
>
> Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
> because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
> notifiers, and hence get_online_cpus() cannot provide the necessary
> synchronization to protect the callback/notifier chains against concurrent
> reads and writes. On the other hand, since the cpu_add_remove_lock protects
> the entire hotplug operation (including CPU_POST_DEAD), we can use
> cpu_maps_update_begin/done() to guarantee proper synchronization.
>
> Also, since cpu_maps_update_begin/done() is like a super-set of
> get/put_online_cpus(), the former naturally protects the critical sections
> from concurrent hotplug operations.
>
> Since the names cpu_maps_update_begin/done() don't make much sense in CPU
> hotplug callback registration scenarios, we'll introduce new APIs named
> cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
>
> In summary, introduce the lockless variants of un/register_cpu_notifier() and
> also export the cpu_notifier_register_begin/done() APIs for use by modules.
> This way, we provide a race-free way to register hotplug callbacks as well as
> perform initialization for the CPUs that are already online.
>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Toshi Kani <[email protected]>
> Cc: "Rafael J. Wysocki" <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Acked-by: Oleg Nesterov <[email protected]>
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
Reviewed-by: Gautham R. Shenoy <[email protected]>
On 02/15/2014 11:51 AM, Srivatsa S. Bhat wrote:
> On 02/14/2014 10:20 PM, Srivatsa S. Bhat wrote:
>> On 02/14/2014 10:19 PM, Boris Ostrovsky wrote:
>>> On 02/14/2014 02:59 AM, Srivatsa S. Bhat wrote:
>>>> Subsystems that want to register CPU hotplug callbacks, as well as
>>>> perform
>>>> initialization for the CPUs that are already online, often do it as shown
>>>> below:
>>>>
> [...]
>>> This looks exactly like the earlier version (i.e the notifier is still
>>> kept registered on allocation failure and commit message doesn't exactly
>>> reflect the change).
>>>
>> Sorry, your earlier reply (for some unknown reason) missed the email-threading
>> and landed elsewhere in my inbox, and hence unfortunately I forgot to take
>> your suggestions into account while sending out the v2.
>>
>> I'll send out an updated version of just this patch, as a reply.
> Here is the updated patch. Please let me know what you think!
Reviewed-by: Boris Ostrovsky <[email protected]>
-boris
>
> ----------------------------------------------------------------------------
>
> From: Srivatsa S. Bhat <[email protected]>
> Subject: [PATCH] xen, balloon: Fix CPU hotplug callback registration
>
> Subsystems that want to register CPU hotplug callbacks, as well as perform
> initialization for the CPUs that are already online, often do it as shown
> below:
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> This is wrong, since it is prone to ABBA deadlocks involving the
> cpu_add_remove_lock and the cpu_hotplug.lock (when running concurrently
> with CPU hotplug operations).
>
> The xen balloon driver doesn't take get/put_online_cpus() around this code,
> but that is also buggy, since it can miss CPU hotplug events in between the
> initialization and callback registration:
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
> ^
> | Race window; Can miss CPU hotplug events here.
> v
> register_cpu_notifier(&foobar_cpu_notifier);
>
> Interestingly, the balloon code in xen can simply be reorganized as shown
> below, to have a race-free method to register hotplug callbacks, without even
> taking get/put_online_cpus(). This is because the initialization performed for
> already online CPUs is exactly the same as that performed for CPUs that come
> online later. Moreover, the code has checks in place to avoid double
> initialization.
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> put_online_cpus();
>
> A hotplug operation that occurs between registering the notifier and calling
> get_online_cpus(), won't disrupt anything, because the code takes care to
> perform the memory allocations only once.
>
> So reorganize the balloon code in xen this way to fix the issues with CPU
> hotplug callback registration.
>
> Cc: Konrad Rzeszutek Wilk <[email protected]>
> Cc: Boris Ostrovsky <[email protected]>
> Cc: David Vrabel <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Cc: [email protected]
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
> ---
>
> drivers/xen/balloon.c | 36 ++++++++++++++++++++++++------------
> 1 file changed, 24 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
> index 37d06ea..dd79549 100644
> --- a/drivers/xen/balloon.c
> +++ b/drivers/xen/balloon.c
> @@ -592,19 +592,29 @@ static void __init balloon_add_region(unsigned long start_pfn,
> }
> }
>
> +static int alloc_balloon_scratch_page(int cpu)
> +{
> + if (per_cpu(balloon_scratch_page, cpu) != NULL)
> + return 0;
> +
> + per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
> + if (per_cpu(balloon_scratch_page, cpu) == NULL) {
> + pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
> + return -ENOMEM;
> + }
> +
> + return 0;
> +}
> +
> +
> static int balloon_cpu_notify(struct notifier_block *self,
> unsigned long action, void *hcpu)
> {
> int cpu = (long)hcpu;
> switch (action) {
> case CPU_UP_PREPARE:
> - if (per_cpu(balloon_scratch_page, cpu) != NULL)
> - break;
> - per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
> - if (per_cpu(balloon_scratch_page, cpu) == NULL) {
> - pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
> + if (alloc_balloon_scratch_page(cpu))
> return NOTIFY_BAD;
> - }
> break;
> default:
> break;
> @@ -624,15 +634,17 @@ static int __init balloon_init(void)
> return -ENODEV;
>
> if (!xen_feature(XENFEAT_auto_translated_physmap)) {
> - for_each_online_cpu(cpu)
> - {
> - per_cpu(balloon_scratch_page, cpu) = alloc_page(GFP_KERNEL);
> - if (per_cpu(balloon_scratch_page, cpu) == NULL) {
> - pr_warn("Failed to allocate balloon_scratch_page for cpu %d\n", cpu);
> + register_cpu_notifier(&balloon_cpu_notifier);
> +
> + get_online_cpus();
> + for_each_online_cpu(cpu) {
> + if (alloc_balloon_scratch_page(cpu)) {
> + put_online_cpus();
> + unregister_cpu_notifier(&balloon_cpu_notifier);
> return -ENOMEM;
> }
> }
> - register_cpu_notifier(&balloon_cpu_notifier);
> + put_online_cpus();
> }
>
> pr_info("Initialising balloon driver\n");
>
>
>
Hi Ingo, Peter, Thomas,
The CPU hotplug core pieces in this patchset have been Acked by Oleg Nesterov
and Gautham Shenoy. A majority of the remaining patches that do the tree-wide
conversions have been Acked by the various subsystem maintainers. Since those
patches have a build dependency on the second patch, it would be easiest to
take all these patches through one single tree.
Would you please consider taking all the patches in this series through your
tree?
Thank you very much!
Regards,
Srivatsa S. Bhat
On Fri, 2014-02-14 at 13:19 +0530, Srivatsa S. Bhat wrote:
> The following method of CPU hotplug callback registration is not safe
> due to the possibility of an ABBA deadlock involving the cpu_add_remove_lock
> and the cpu_hotplug.lock.
>
> get_online_cpus();
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> register_cpu_notifier(&foobar_cpu_notifier);
>
> put_online_cpus();
>
> The deadlock is shown below:
>
> CPU 0 CPU 1
> ----- -----
>
> Acquire cpu_hotplug.lock
> [via get_online_cpus()]
>
> CPU online/offline operation
> takes cpu_add_remove_lock
> [via cpu_maps_update_begin()]
>
>
> Try to acquire
> cpu_add_remove_lock
> [via register_cpu_notifier()]
>
>
> CPU online/offline operation
> tries to acquire cpu_hotplug.lock
> [via cpu_hotplug_begin()]
>
>
> *** DEADLOCK! ***
>
> The problem here is that callback registration takes the locks in one order
> whereas the CPU hotplug operations take the same locks in the opposite order.
> To avoid this issue and to provide a race-free method to register CPU hotplug
> callbacks (along with initialization of already online CPUs), introduce new
> variants of the callback registration APIs that simply register the callbacks
> without holding the cpu_add_remove_lock during the registration. That way,
> we can avoid the ABBA scenario. However, we will need to hold the
> cpu_add_remove_lock throughout the entire critical section, to protect updates
> to the callback/notifier chain.
>
> This can be achieved by writing the callback registration code as follows:
>
> cpu_maps_update_begin(); [ or cpu_notifier_register_begin(); see below ]
>
> for_each_online_cpu(cpu)
> init_cpu(cpu);
>
> /* This doesn't take the cpu_add_remove_lock */
> __register_cpu_notifier(&foobar_cpu_notifier);
>
> cpu_maps_update_done(); [ or cpu_notifier_register_done(); see below ]
>
> Note that we can't use get_online_cpus() here instead of cpu_maps_update_begin()
> because the cpu_hotplug.lock is dropped during the invocation of CPU_POST_DEAD
> notifiers, and hence get_online_cpus() cannot provide the necessary
> synchronization to protect the callback/notifier chains against concurrent
> reads and writes. On the other hand, since the cpu_add_remove_lock protects
> the entire hotplug operation (including CPU_POST_DEAD), we can use
> cpu_maps_update_begin/done() to guarantee proper synchronization.
>
> Also, since cpu_maps_update_begin/done() is like a super-set of
> get/put_online_cpus(), the former naturally protects the critical sections
> from concurrent hotplug operations.
>
> Since the names cpu_maps_update_begin/done() don't make much sense in CPU
> hotplug callback registration scenarios, we'll introduce new APIs named
> cpu_notifier_register_begin/done() and map them to cpu_maps_update_begin/done().
>
> In summary, introduce the lockless variants of un/register_cpu_notifier() and
> also export the cpu_notifier_register_begin/done() APIs for use by modules.
> This way, we provide a race-free way to register hotplug callbacks as well as
> perform initialization for the CPUs that are already online.
>
> Cc: Thomas Gleixner <[email protected]>
> Cc: Toshi Kani <[email protected]>
> Cc: "Rafael J. Wysocki" <[email protected]>
> Cc: Andrew Morton <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Ingo Molnar <[email protected]>
> Acked-by: Oleg Nesterov <[email protected]>
> Signed-off-by: Srivatsa S. Bhat <[email protected]>
Acked-by: Toshi Kani <[email protected]>
Thanks,
-Toshi