changes since v3:
* put simple bugfixes first
* move common part of syncing with master CPU in cpu_init()
for x32/64 variant into helper function
* cpu_init(): WARN_ON if cpu_initialized_mask is set
* fix panic on CPU unplug, caused by erroneous removing
of "pr->dev = dev;" in drivers/acpi/acpi_processor.c
--
Hang is observed on virtual machines during CPU hotplug,
especially in big guests with many CPUs. (It happens more
often if host is over-committed).
Hang happens because master CPU timeouts on waiting till
AP boots and 'cancels' CPU online operation assuming AP
is not functional but AP may continue run wild later
causing various hangs or panics in running kernel that
is assuming that AP was offline.
This is an alternative approach, that instead of canceling
in-progress AP bringup (https://lkml.org/lkml/2014/3/6/257),
removes timeouts so that AP bringup won't be affected by
poor timing and syncs AP with master CPU at early startup
making sure that AP won't run wild if master CPU doesn't
expect AP to come online.
Series also fixes 3 bugs found during testing CPU bringup
failure case.
--
Below is the detailed description of a more often happening hang:
---
Master CPU may timeout before cpu_callin_mask is set and cancel
booting CPU, but being onlined CPU still continues to boot, sets
cpu_active_mask (CPU_STARTING notifiers) and spins in
check_tsc_sync_target() for master cpu to arrive. Following attempt
to online another cpu hangs in stop_machine, initiated from here:
smp_callin ->
smp_store_cpu_info ->
identify_secondary_cpu ->
mtrr_ap_init -> set_mtrr_from_inactive_cpu
stop_machine waits on completion of stop_work on all CPUs from
cpu_active_mask including a failed CPU that spins in check_tsc_sync_target().
Igor Mammedov (5):
x86: fix list corruption on CPU hotplug
x86: fix memory corruption in acpi_unmap_lsapic()
acpi_processor: do not mark present at boot but not onlined CPU as
onlined
x86: log error on secondary CPU wakeup failure at ERR level
x86: initialize secondary CPU only if master CPU will wait for it
arch/x86/kernel/cpu/common.c | 27 ++++++----
arch/x86/kernel/smpboot.c | 103 ++++++++++++----------------------------
drivers/acpi/acpi_processor.c | 1 -
3 files changed, 47 insertions(+), 84 deletions(-)
If system is running without debug level logging,
it will not log error if do_boot_cpu() failed to
wakeup AP. It may lead to silent AP bringup
failures at boot time.
Change message level to KERN_ERR to make error
visible to user as it's done on other architectures.
Signed-off-by: Igor Mammedov <[email protected]>
---
arch/x86/kernel/smpboot.c | 2 +-
1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 2988f69..ae2fd97 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -918,7 +918,7 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
err = do_boot_cpu(apicid, cpu, tidle);
if (err) {
- pr_debug("do_boot_cpu failed %d\n", err);
+ pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu);
return -EIO;
}
--
1.7.1
currently if AP wake up is failed, master CPU marks AP as not present
in do_boot_cpu() by calling set_cpu_present(cpu, false).
That leads to following list corruption on the next physical CPU
hotplug:
[ 418.107336] WARNING: CPU: 1 PID: 45 at lib/list_debug.c:33 __list_add+0xbe/0xd0()
[ 418.115268] list_add corruption. prev->next should be next (ffff88003dc57600), but was ffff88003e20c3a0. (prev=ffff88003e20c3a0).
[ 418.123693] Modules linked in: nf_conntrack_netbios_ns nf_conntrack_broadcast ipt_MASQUERADE ip6t_REJECT ipt_REJECT cfg80211 xt_conntrack rfkill ee
[ 418.138979] CPU: 1 PID: 45 Comm: kworker/u10:1 Not tainted 3.14.0-rc6+ #387
[ 418.149989] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2007
[ 418.165750] Workqueue: kacpi_hotplug acpi_hotplug_work_fn
[ 418.166433] 0000000000000021 ffff880038ca7988 ffffffff8159b22d 0000000000000021
[ 418.176460] ffff880038ca79d8 ffff880038ca79c8 ffffffff8106942c ffff880038ca79e8
[ 418.177453] ffff88003e20c3a0 ffff88003dc57600 ffff88003e20c3a0 00000000ffffffea
[ 418.178445] Call Trace:
[ 418.185811] [<ffffffff8159b22d>] dump_stack+0x49/0x5c
[ 418.186440] [<ffffffff8106942c>] warn_slowpath_common+0x8c/0xc0
[ 418.187192] [<ffffffff81069516>] warn_slowpath_fmt+0x46/0x50
[ 418.191231] [<ffffffff8136ef51>] ? acpi_ns_get_node+0xb7/0xc7
[ 418.193889] [<ffffffff812f796e>] __list_add+0xbe/0xd0
[ 418.196649] [<ffffffff812e2aa9>] kobject_add_internal+0x79/0x200
[ 418.208610] [<ffffffff812e2e18>] kobject_add_varg+0x38/0x60
[ 418.213831] [<ffffffff812e2ef4>] kobject_add+0x44/0x70
[ 418.229961] [<ffffffff813e2c60>] device_add+0xd0/0x550
[ 418.234991] [<ffffffff813f0e95>] ? pm_runtime_init+0xe5/0xf0
[ 418.250226] [<ffffffff813e32be>] device_register+0x1e/0x30
[ 418.255296] [<ffffffff813e82a3>] register_cpu+0xe3/0x130
[ 418.266539] [<ffffffff81592be5>] arch_register_cpu+0x65/0x150
[ 418.285845] [<ffffffff81355c0d>] acpi_processor_hotadd_init+0x5a/0x9b
...
Which is caused by the fact that generic_processor_info() allocates
logical CPU id by calling:
cpu = cpumask_next_zero(-1, cpu_present_mask);
which returns id of previously failed to wake up CPU, since its bit
is cleared by do_boot_cpu() and as result register_cpu() tries to
register another CPU with the same id as already present but failed
to be onlined CPU.
Taking in account that AP will not do anything if master CPU failed to
wake it up, there is no reason to mark that AP as not present and
break next cpu hotplug attempts. As a side effect of not marking AP
as not present, user would be allowed to online it again later.
Signed-off-by: Igor Mammedov <[email protected]>
---
arch/x86/kernel/smpboot.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 3482693..6124f15 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -860,7 +860,6 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
/* was set by cpu_init() */
cpumask_clear_cpu(cpu, cpu_initialized_mask);
- set_cpu_present(cpu, false);
per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID;
}
--
1.7.1
Hang is observed on virtual machines during CPU hotplug,
especially in big guests with many CPUs. (It reproducible
more often if host is over-committed).
It happens because master CPU gives up waiting on
secondary CPU and allows it to run wild. As result
AP causes locking or crashing system. For example
as described here: https://lkml.org/lkml/2014/3/6/257
If master CPU have sent STARTUP IPI successfully,
and AP signalled to master CPU that it's ready
to start initialization, make master CPU wait
indefinitely till AP is onlined.
To ensure that AP won't ever run wild, make it
wait at early startup till master CPU confirms its
intention to wait for AP.
Signed-off-by: Igor Mammedov <[email protected]>
---
v2:
- ammend comment in cpu_init()
v3:
- leave timeouts in do_boot_cpu(), so that master CPU
won't hang if AP doesn't respond, use cpu_initialized_mask
as a way for AP to signal to master CPU that it's ready
to start initialzation.
v4:
- move common code in cpu_init() for x32/x64 in shared
helper function wait_for_master_cpu()
- add WARN_ON(cpumask_test_and_set_cpu(cpu, cpu_initialized_mask))
to wait_formaster_cpu()
---
arch/x86/kernel/cpu/common.c | 27 +++++++-----
arch/x86/kernel/smpboot.c | 98 +++++++++++++-----------------------------
2 files changed, 46 insertions(+), 79 deletions(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a135239..a4bcbac 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1221,6 +1221,17 @@ static void dbg_restore_debug_regs(void)
#define dbg_restore_debug_regs()
#endif /* ! CONFIG_KGDB */
+static void wait_for_master_cpu(int cpu)
+{
+ /*
+ * wait for ACK from master CPU before continuing
+ * with AP initialization
+ */
+ WARN_ON(cpumask_test_and_set_cpu(cpu, cpu_initialized_mask));
+ while (!cpumask_test_cpu(cpu, cpu_callout_mask))
+ cpu_relax();
+}
+
/*
* cpu_init() initializes state that is per-CPU. Some data is already
* initialized (naturally) in the bootstrap process, such as the GDT
@@ -1236,16 +1247,17 @@ void cpu_init(void)
struct task_struct *me;
struct tss_struct *t;
unsigned long v;
- int cpu;
+ int cpu = stack_smp_processor_id();
int i;
+ wait_for_master_cpu(cpu);
+
/*
* Load microcode on this cpu if a valid microcode is available.
* This is early microcode loading procedure.
*/
load_ucode_ap();
- cpu = stack_smp_processor_id();
t = &per_cpu(init_tss, cpu);
oist = &per_cpu(orig_ist, cpu);
@@ -1257,9 +1269,6 @@ void cpu_init(void)
me = current;
- if (cpumask_test_and_set_cpu(cpu, cpu_initialized_mask))
- panic("CPU#%d already initialized!\n", cpu);
-
pr_debug("Initializing CPU#%d\n", cpu);
clear_in_cr4(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE);
@@ -1336,13 +1345,9 @@ void cpu_init(void)
struct tss_struct *t = &per_cpu(init_tss, cpu);
struct thread_struct *thread = &curr->thread;
- show_ucode_info_early();
+ wait_for_master_cpu(cpu);
- if (cpumask_test_and_set_cpu(cpu, cpu_initialized_mask)) {
- printk(KERN_WARNING "CPU#%d already initialized!\n", cpu);
- for (;;)
- local_irq_enable();
- }
+ show_ucode_info_early();
printk(KERN_INFO "Initializing CPU#%d\n", cpu);
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index ae2fd97..44903ad 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -111,7 +111,6 @@ atomic_t init_deasserted;
static void smp_callin(void)
{
int cpuid, phys_id;
- unsigned long timeout;
/*
* If waken up by an INIT in an 82489DX configuration
@@ -130,37 +129,6 @@ static void smp_callin(void)
* (This works even if the APIC is not enabled.)
*/
phys_id = read_apic_id();
- if (cpumask_test_cpu(cpuid, cpu_callin_mask)) {
- panic("%s: phys CPU#%d, CPU#%d already present??\n", __func__,
- phys_id, cpuid);
- }
- pr_debug("CPU#%d (phys ID: %d) waiting for CALLOUT\n", cpuid, phys_id);
-
- /*
- * STARTUP IPIs are fragile beasts as they might sometimes
- * trigger some glue motherboard logic. Complete APIC bus
- * silence for 1 second, this overestimates the time the
- * boot CPU is spending to send the up to 2 STARTUP IPIs
- * by a factor of two. This should be enough.
- */
-
- /*
- * Waiting 2s total for startup (udelay is not yet working)
- */
- timeout = jiffies + 2*HZ;
- while (time_before(jiffies, timeout)) {
- /*
- * Has the boot CPU finished it's STARTUP sequence?
- */
- if (cpumask_test_cpu(cpuid, cpu_callout_mask))
- break;
- cpu_relax();
- }
-
- if (!time_before(jiffies, timeout)) {
- panic("%s: CPU%d started up but did not get a callout!\n",
- __func__, cpuid);
- }
/*
* the boot CPU has finished the init stage and is spinning
@@ -750,8 +718,8 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
unsigned long start_ip = real_mode_header->trampoline_start;
unsigned long boot_error = 0;
- int timeout;
int cpu0_nmi_registered = 0;
+ unsigned long timeout;
/* Just in case we booted with a single CPU. */
alternatives_enable_smp();
@@ -799,6 +767,14 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
}
/*
+ * AP might wait on cpu_callout_mask in cpu_init() with
+ * cpu_initialized_mask set if previous attempt to online
+ * it timed-out. Clear cpu_initialized_mask so that after
+ * INIT/SIPI it could start with a clean state.
+ */
+ cpumask_clear_cpu(cpu, cpu_initialized_mask);
+
+ /*
* Wake up a CPU in difference cases:
* - Use the method in the APIC driver if it's defined
* Otherwise,
@@ -810,55 +786,41 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
boot_error = wakeup_cpu_via_init_nmi(cpu, start_ip, apicid,
&cpu0_nmi_registered);
+
if (!boot_error) {
/*
- * allow APs to start initializing.
+ * Wait 10s total for a response from AP
*/
- pr_debug("Before Callout %d\n", cpu);
- cpumask_set_cpu(cpu, cpu_callout_mask);
- pr_debug("After Callout %d\n", cpu);
+ boot_error = -1;
+ timeout = jiffies + 10*HZ;
+ while (time_before(jiffies, timeout)) {
+ if (cpumask_test_cpu(cpu, cpu_initialized_mask)) {
+ /*
+ * Tell AP to proceed with initialization
+ */
+ cpumask_set_cpu(cpu, cpu_callout_mask);
+ boot_error = 0;
+ break;
+ }
+ udelay(100);
+ schedule();
+ }
+ }
+ if (!boot_error) {
/*
- * Wait 5s total for a response
+ * Wait till AP completes initial initialization
*/
- for (timeout = 0; timeout < 50000; timeout++) {
- if (cpumask_test_cpu(cpu, cpu_callin_mask))
- break; /* It has booted */
- udelay(100);
+ while (!cpumask_test_cpu(cpu, cpu_callin_mask)) {
/*
* Allow other tasks to run while we wait for the
* AP to come online. This also gives a chance
* for the MTRR work(triggered by the AP coming online)
* to be completed in the stop machine context.
*/
+ udelay(100);
schedule();
}
-
- if (cpumask_test_cpu(cpu, cpu_callin_mask)) {
- print_cpu_msr(&cpu_data(cpu));
- pr_debug("CPU%d: has booted.\n", cpu);
- } else {
- boot_error = 1;
- if (*trampoline_status == 0xA5A5A5A5)
- /* trampoline started but...? */
- pr_err("CPU%d: Stuck ??\n", cpu);
- else
- /* trampoline code not run */
- pr_err("CPU%d: Not responding\n", cpu);
- if (apic->inquire_remote_apic)
- apic->inquire_remote_apic(apicid);
- }
- }
-
- if (boot_error) {
- /* Try to put things back the way they were before ... */
- numa_remove_cpu(cpu); /* was set by numa_add_cpu */
-
- /* was set by do_boot_cpu() */
- cpumask_clear_cpu(cpu, cpu_callout_mask);
-
- /* was set by cpu_init() */
- cpumask_clear_cpu(cpu, cpu_initialized_mask);
}
/* mark "stuck" area as not stuck */
--
1.7.1
if during CPU hotplug master CPU failed to wake up AP
it set percpu x86_cpu_to_apicid to BAD_APICID=0xFFFF for AP.
However following attempt to unplug that CPU will lead to
out of bound write access to __apicid_to_node[] which is
32768 items long on x86_64 kernel.
So drop setting x86_cpu_to_apicid to BAD_APICID in do_boot_cpu()
and allow acpi_processor_remove()->acpi_unmap_lsapic() cleanly
remove CPU.
Signed-off-by: Igor Mammedov <[email protected]>
---
arch/x86/kernel/smpboot.c | 2 --
1 files changed, 0 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 6124f15..2988f69 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -859,8 +859,6 @@ static int do_boot_cpu(int apicid, int cpu, struct task_struct *idle)
/* was set by cpu_init() */
cpumask_clear_cpu(cpu, cpu_initialized_mask);
-
- per_cpu(x86_cpu_to_apicid, cpu) = BAD_APICID;
}
/* mark "stuck" area as not stuck */
--
1.7.1
acpi_processor_add() assumes that present at boot CPUs
are always onlined, it is not so if a CPU failed to become
onlined. As result acpi_processor_add() will mark such CPU
device as onlined in sysfs and following attempts to
online/offline it using /sys/device/system/cpu/cpuX/online
attribute will fail.
Do not poke into device internals in acpi_processor_add()
and touch "struct device { .offline }" attribute, since
for CPUs onlined at boot it's set by:
topology_init() -> arch_register_cpu() -> register_cpu()
before ACPI device tree is parsed, and for hotplugged
CPUs it's set when userspace onlines CPU via sysfs.
Signed-off-by: Igor Mammedov <[email protected]>
---
v2:
- fix regression in v1 leading to NULL pointer dereference
on CPU unplug, do not remove "pr->dev = dev;"
---
drivers/acpi/acpi_processor.c | 1 -
1 files changed, 0 insertions(+), 1 deletions(-)
diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
index c29c2c3..42d66f8 100644
--- a/drivers/acpi/acpi_processor.c
+++ b/drivers/acpi/acpi_processor.c
@@ -404,7 +404,6 @@ static int acpi_processor_add(struct acpi_device *device,
goto err;
pr->dev = dev;
- dev->offline = pr->flags.need_hotplug_init;
/* Trigger the processor driver's .probe() if present. */
if (device_attach(dev) >= 0)
--
1.7.1
On Monday, April 14, 2014 05:11:15 PM Igor Mammedov wrote:
> acpi_processor_add() assumes that present at boot CPUs
> are always onlined, it is not so if a CPU failed to become
> onlined. As result acpi_processor_add() will mark such CPU
> device as onlined in sysfs and following attempts to
> online/offline it using /sys/device/system/cpu/cpuX/online
> attribute will fail.
>
> Do not poke into device internals in acpi_processor_add()
> and touch "struct device { .offline }" attribute, since
> for CPUs onlined at boot it's set by:
> topology_init() -> arch_register_cpu() -> register_cpu()
> before ACPI device tree is parsed, and for hotplugged
> CPUs it's set when userspace onlines CPU via sysfs.
>
> Signed-off-by: Igor Mammedov <[email protected]>
> ---
> v2:
> - fix regression in v1 leading to NULL pointer dereference
> on CPU unplug, do not remove "pr->dev = dev;"
Yeah.
Does this patch depend on any other patches in the series?
I don't think so, but just asking.
If it doesn't, why is it part of this series at all?
> ---
> drivers/acpi/acpi_processor.c | 1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index c29c2c3..42d66f8 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -404,7 +404,6 @@ static int acpi_processor_add(struct acpi_device *device,
> goto err;
>
> pr->dev = dev;
> - dev->offline = pr->flags.need_hotplug_init;
>
> /* Trigger the processor driver's .probe() if present. */
> if (device_attach(dev) >= 0)
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
On Monday, April 14, 2014 05:11:15 PM Igor Mammedov wrote:
> acpi_processor_add() assumes that present at boot CPUs
> are always onlined, it is not so if a CPU failed to become
> onlined. As result acpi_processor_add() will mark such CPU
> device as onlined in sysfs and following attempts to
> online/offline it using /sys/device/system/cpu/cpuX/online
> attribute will fail.
>
> Do not poke into device internals in acpi_processor_add()
> and touch "struct device { .offline }" attribute, since
> for CPUs onlined at boot it's set by:
> topology_init() -> arch_register_cpu() -> register_cpu()
> before ACPI device tree is parsed, and for hotplugged
> CPUs it's set when userspace onlines CPU via sysfs.
>
> Signed-off-by: Igor Mammedov <[email protected]>
> ---
> v2:
> - fix regression in v1 leading to NULL pointer dereference
> on CPU unplug, do not remove "pr->dev = dev;"
> ---
> drivers/acpi/acpi_processor.c | 1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index c29c2c3..42d66f8 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -404,7 +404,6 @@ static int acpi_processor_add(struct acpi_device *device,
> goto err;
>
> pr->dev = dev;
> - dev->offline = pr->flags.need_hotplug_init;
This line is to ensure that dev->offline and pr->flags.need_hotplug_init are
consistent with each other. If you remove it, you need to ensure that they
will be consistent in some other way.
>
> /* Trigger the processor driver's .probe() if present. */
> if (device_attach(dev) >= 0)
>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
On Tue, 15 Apr 2014 07:48:30 +0200
"Rafael J. Wysocki" <[email protected]> wrote:
> On Monday, April 14, 2014 05:11:15 PM Igor Mammedov wrote:
> > acpi_processor_add() assumes that present at boot CPUs
> > are always onlined, it is not so if a CPU failed to become
> > onlined. As result acpi_processor_add() will mark such CPU
> > device as onlined in sysfs and following attempts to
> > online/offline it using /sys/device/system/cpu/cpuX/online
> > attribute will fail.
> >
> > Do not poke into device internals in acpi_processor_add()
> > and touch "struct device { .offline }" attribute, since
> > for CPUs onlined at boot it's set by:
> > topology_init() -> arch_register_cpu() -> register_cpu()
> > before ACPI device tree is parsed, and for hotplugged
> > CPUs it's set when userspace onlines CPU via sysfs.
> >
> > Signed-off-by: Igor Mammedov <[email protected]>
> > ---
> > v2:
> > - fix regression in v1 leading to NULL pointer dereference
> > on CPU unplug, do not remove "pr->dev = dev;"
>
> Yeah.
>
> Does this patch depend on any other patches in the series?
>
> I don't think so, but just asking.
>
> If it doesn't, why is it part of this series at all?
It's doesn't depend on any other patches in here, it was just
convenient to post it as a part of fixes found in CPU hotplug
code and nothing more.
>
> > ---
> > drivers/acpi/acpi_processor.c | 1 -
> > 1 files changed, 0 insertions(+), 1 deletions(-)
> >
> > diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> > index c29c2c3..42d66f8 100644
> > --- a/drivers/acpi/acpi_processor.c
> > +++ b/drivers/acpi/acpi_processor.c
> > @@ -404,7 +404,6 @@ static int acpi_processor_add(struct acpi_device *device,
> > goto err;
> >
> > pr->dev = dev;
> > - dev->offline = pr->flags.need_hotplug_init;
> >
> > /* Trigger the processor driver's .probe() if present. */
> > if (device_attach(dev) >= 0)
> >
>
* Rafael J. Wysocki <[email protected]> wrote:
> On Monday, April 14, 2014 05:11:15 PM Igor Mammedov wrote:
> > acpi_processor_add() assumes that present at boot CPUs
> > are always onlined, it is not so if a CPU failed to become
> > onlined. As result acpi_processor_add() will mark such CPU
> > device as onlined in sysfs and following attempts to
> > online/offline it using /sys/device/system/cpu/cpuX/online
> > attribute will fail.
> >
> > Do not poke into device internals in acpi_processor_add()
> > and touch "struct device { .offline }" attribute, since
> > for CPUs onlined at boot it's set by:
> > topology_init() -> arch_register_cpu() -> register_cpu()
> > before ACPI device tree is parsed, and for hotplugged
> > CPUs it's set when userspace onlines CPU via sysfs.
> >
> > Signed-off-by: Igor Mammedov <[email protected]>
> > ---
> > v2:
> > - fix regression in v1 leading to NULL pointer dereference
> > on CPU unplug, do not remove "pr->dev = dev;"
>
> Yeah.
>
> Does this patch depend on any other patches in the series?
>
> I don't think so, but just asking.
>
> If it doesn't, why is it part of this series at all?
I suspect because Igor was rigorously stress-testing CPU hotplug, and
was fixing all the bugs he saw, before adding the one feature he is
interested in.
The feature cannot be guaranteed to be correct, without having a
stable base to work on.
As such this series makes sense, as long as the fixes precede the
feature, and as long as the fixes are correct.
Consider it work in progress, with you being one of the reviewers who
makes sure the fixes are correct.
Thanks,
Ingo
On Tuesday, April 15, 2014 08:04:11 AM Ingo Molnar wrote:
>
> * Rafael J. Wysocki <[email protected]> wrote:
>
> > On Monday, April 14, 2014 05:11:15 PM Igor Mammedov wrote:
> > > acpi_processor_add() assumes that present at boot CPUs
> > > are always onlined, it is not so if a CPU failed to become
> > > onlined. As result acpi_processor_add() will mark such CPU
> > > device as onlined in sysfs and following attempts to
> > > online/offline it using /sys/device/system/cpu/cpuX/online
> > > attribute will fail.
> > >
> > > Do not poke into device internals in acpi_processor_add()
> > > and touch "struct device { .offline }" attribute, since
> > > for CPUs onlined at boot it's set by:
> > > topology_init() -> arch_register_cpu() -> register_cpu()
> > > before ACPI device tree is parsed, and for hotplugged
> > > CPUs it's set when userspace onlines CPU via sysfs.
> > >
> > > Signed-off-by: Igor Mammedov <[email protected]>
> > > ---
> > > v2:
> > > - fix regression in v1 leading to NULL pointer dereference
> > > on CPU unplug, do not remove "pr->dev = dev;"
> >
> > Yeah.
> >
> > Does this patch depend on any other patches in the series?
> >
> > I don't think so, but just asking.
> >
> > If it doesn't, why is it part of this series at all?
>
> I suspect because Igor was rigorously stress-testing CPU hotplug, and
> was fixing all the bugs he saw, before adding the one feature he is
> interested in.
>
> The feature cannot be guaranteed to be correct, without having a
> stable base to work on.
>
> As such this series makes sense, as long as the fixes precede the
> feature, and as long as the fixes are correct.
>
> Consider it work in progress, with you being one of the reviewers who
> makes sure the fixes are correct.
Fair enough.
So perhaps the subject of the whole series should be changed, because x86 is
not the only architecture affected by this particular patch?
Rafael
On Mon, 2014-04-14 at 17:11 +0200, Igor Mammedov wrote:
> currently if AP wake up is failed, master CPU marks AP as not present
> in do_boot_cpu() by calling set_cpu_present(cpu, false).
> That leads to following list corruption on the next physical CPU
> hotplug:
>
> [ 418.107336] WARNING: CPU: 1 PID: 45 at lib/list_debug.c:33 __list_add+0xbe/0xd0()
> [ 418.115268] list_add corruption. prev->next should be next (ffff88003dc57600), but was ffff88003e20c3a0. (prev=ffff88003e20c3a0).
> [ 418.123693] Modules linked in: nf_conntrack_netbios_ns nf_conntrack_broadcast ipt_MASQUERADE ip6t_REJECT ipt_REJECT cfg80211 xt_conntrack rfkill ee
> [ 418.138979] CPU: 1 PID: 45 Comm: kworker/u10:1 Not tainted 3.14.0-rc6+ #387
> [ 418.149989] Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2007
> [ 418.165750] Workqueue: kacpi_hotplug acpi_hotplug_work_fn
> [ 418.166433] 0000000000000021 ffff880038ca7988 ffffffff8159b22d 0000000000000021
> [ 418.176460] ffff880038ca79d8 ffff880038ca79c8 ffffffff8106942c ffff880038ca79e8
> [ 418.177453] ffff88003e20c3a0 ffff88003dc57600 ffff88003e20c3a0 00000000ffffffea
> [ 418.178445] Call Trace:
> [ 418.185811] [<ffffffff8159b22d>] dump_stack+0x49/0x5c
> [ 418.186440] [<ffffffff8106942c>] warn_slowpath_common+0x8c/0xc0
> [ 418.187192] [<ffffffff81069516>] warn_slowpath_fmt+0x46/0x50
> [ 418.191231] [<ffffffff8136ef51>] ? acpi_ns_get_node+0xb7/0xc7
> [ 418.193889] [<ffffffff812f796e>] __list_add+0xbe/0xd0
> [ 418.196649] [<ffffffff812e2aa9>] kobject_add_internal+0x79/0x200
> [ 418.208610] [<ffffffff812e2e18>] kobject_add_varg+0x38/0x60
> [ 418.213831] [<ffffffff812e2ef4>] kobject_add+0x44/0x70
> [ 418.229961] [<ffffffff813e2c60>] device_add+0xd0/0x550
> [ 418.234991] [<ffffffff813f0e95>] ? pm_runtime_init+0xe5/0xf0
> [ 418.250226] [<ffffffff813e32be>] device_register+0x1e/0x30
> [ 418.255296] [<ffffffff813e82a3>] register_cpu+0xe3/0x130
> [ 418.266539] [<ffffffff81592be5>] arch_register_cpu+0x65/0x150
> [ 418.285845] [<ffffffff81355c0d>] acpi_processor_hotadd_init+0x5a/0x9b
> ...
> Which is caused by the fact that generic_processor_info() allocates
> logical CPU id by calling:
>
> cpu = cpumask_next_zero(-1, cpu_present_mask);
>
> which returns id of previously failed to wake up CPU, since its bit
> is cleared by do_boot_cpu() and as result register_cpu() tries to
> register another CPU with the same id as already present but failed
> to be onlined CPU.
>
> Taking in account that AP will not do anything if master CPU failed to
> wake it up, there is no reason to mark that AP as not present and
> break next cpu hotplug attempts. As a side effect of not marking AP
> as not present, user would be allowed to online it again later.
>
> Signed-off-by: Igor Mammedov <[email protected]>
Hi Igor,
Sorry for long delay... Can you please combine patch 1/5 and 2/5? When
a CPU is marked as present, its APIC ID must be valid. So, it does not
make sense to separate patch 1/5 and 2/5. With that change:
Acked-by: Toshi Kani <[email protected]>
Thanks,
-Toshi
On Mon, 2014-04-14 at 17:11 +0200, Igor Mammedov wrote:
> acpi_processor_add() assumes that present at boot CPUs
> are always onlined, it is not so if a CPU failed to become
> onlined. As result acpi_processor_add() will mark such CPU
> device as onlined in sysfs and following attempts to
> online/offline it using /sys/device/system/cpu/cpuX/online
> attribute will fail.
>
> Do not poke into device internals in acpi_processor_add()
> and touch "struct device { .offline }" attribute, since
> for CPUs onlined at boot it's set by:
> topology_init() -> arch_register_cpu() -> register_cpu()
> before ACPI device tree is parsed, and for hotplugged
> CPUs it's set when userspace onlines CPU via sysfs.
>
> Signed-off-by: Igor Mammedov <[email protected]>
> ---
> v2:
> - fix regression in v1 leading to NULL pointer dereference
> on CPU unplug, do not remove "pr->dev = dev;"
> ---
> drivers/acpi/acpi_processor.c | 1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/acpi/acpi_processor.c b/drivers/acpi/acpi_processor.c
> index c29c2c3..42d66f8 100644
> --- a/drivers/acpi/acpi_processor.c
> +++ b/drivers/acpi/acpi_processor.c
> @@ -404,7 +404,6 @@ static int acpi_processor_add(struct acpi_device *device,
> goto err;
>
> pr->dev = dev;
> - dev->offline = pr->flags.need_hotplug_init;
IIRC, this change was necessary to handle the case when maxcpus=X is
specified at boot. In this case, excessive CPU's dev->offline needs to
be set to 1. Can you verify this?
Thanks,
-Toshi
On Mon, 2014-04-14 at 17:11 +0200, Igor Mammedov wrote:
> If system is running without debug level logging,
> it will not log error if do_boot_cpu() failed to
> wakeup AP. It may lead to silent AP bringup
> failures at boot time.
> Change message level to KERN_ERR to make error
> visible to user as it's done on other architectures.
>
> Signed-off-by: Igor Mammedov <[email protected]>
> ---
> arch/x86/kernel/smpboot.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 2988f69..ae2fd97 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -918,7 +918,7 @@ int native_cpu_up(unsigned int cpu, struct task_struct *tidle)
>
> err = do_boot_cpu(apicid, cpu, tidle);
> if (err) {
> - pr_debug("do_boot_cpu failed %d\n", err);
> + pr_err("do_boot_cpu failed(%d) to wakeup CPU#%u\n", err, cpu);
> return -EIO;
> }
>
Looks good.
Acked-by: Toshi Kani <[email protected]>
I will review patch 5/5 later (probably tomorrow).
Thanks,
-Toshi