Hi Andrew,
Find attached the i386 cpu hotplug patch updated for Ingo's latest
round of goodies. In order to avoid dumping cpu hotplug code into
kernel/irq/* i dropped the cpu_online check in do_IRQ() by modifying
fixup_irqs(). The difference being that on cpu offline, fixup_irqs() is
called before we clear the cpu from cpu_online_map and a long delay in
order to ensure that we never have any queued external interrupts on the
APICs. Due to my usual test victims being in boxes a continent away this
hasn't been tested, but i'll cover bug reports (nudge, Nathan! ;)
1) Add CONFIG_HOTPLUG_CPU
2) disable local APIC timer on dead cpus.
3) Disable preempt around irq balancing to prevent CPUs going down.
4) Print irq stats for all possible cpus.
5) Debugging check for interrupts on offline cpus.
6) Hacky fixup_irqs() to redirect irqs when cpus go off/online.
7) play_dead() for offline cpus to spin inside.
8) Handle offline cpus set in flush_tlb_others().
9) Grab lock earlier in smp_call_function() to prevent CPUs going down.
10) Implement __cpu_disable() and __cpu_die().
11) Enable local interrupts in cpu_enable() after fixup_irqs()
12) Don't fiddle with NMI on dead cpu, but leave intact on other cpus.
13) Program IRQ affinity whilst cpu is still in cpu_online_map on offline.
Signed-off-by: Zwane Mwaikambo <[email protected]>
arch/i386/Kconfig | 9 ++++
arch/i386/kernel/apic.c | 3 -
arch/i386/kernel/io_apic.c | 2
arch/i386/kernel/irq.c | 66 +++++++++++++++++++++++++------
arch/i386/kernel/msr.c | 2
arch/i386/kernel/process.c | 34 ++++++++++++++++
arch/i386/kernel/smp.c | 25 +++++++----
arch/i386/kernel/smpboot.c | 94 ++++++++++++++++++++++++++++++++++++++++++---
arch/i386/kernel/traps.c | 8 +++
arch/ia64/kernel/smpboot.c | 3 -
arch/ppc64/kernel/smp.c | 4 +
arch/s390/kernel/smp.c | 4 +
include/asm-i386/cpu.h | 2
include/asm-i386/irq.h | 4 +
include/asm-i386/smp.h | 3 +
kernel/cpu.c | 14 ++----
16 files changed, 236 insertions(+), 41 deletions(-)
Index: linux-2.6.9-rc3-mm3/arch/i386/Kconfig
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/Kconfig,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 Kconfig
--- linux-2.6.9-rc3-mm3/arch/i386/Kconfig 8 Oct 2004 10:56:05 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/Kconfig 10 Oct 2004 18:31:21 -0000
@@ -1218,6 +1218,15 @@ config SCx200
This support is also available as a module. If compiled as a
module, it will be called scx200.
+config HOTPLUG_CPU
+ bool "Support for hot-pluggable CPUs (EXPERIMENTAL)"
+ depends on SMP && HOTPLUG && EXPERIMENTAL
+ ---help---
+ Say Y here to experiment with turning CPUs off and on. CPUs
+ can be controlled through /sys/devices/system/cpu.
+
+ Say N.
+
source "drivers/pcmcia/Kconfig"
source "drivers/pci/hotplug/Kconfig"
Index: linux-2.6.9-rc3-mm3/arch/i386/kernel/apic.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/kernel/apic.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 apic.c
--- linux-2.6.9-rc3-mm3/arch/i386/kernel/apic.c 8 Oct 2004 10:56:07 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/kernel/apic.c 10 Oct 2004 18:31:21 -0000
@@ -26,6 +26,7 @@
#include <linux/mc146818rtc.h>
#include <linux/kernel_stat.h>
#include <linux/sysdev.h>
+#include <linux/cpu.h>
#include <asm/atomic.h>
#include <asm/smp.h>
@@ -1055,7 +1056,7 @@ void __init setup_secondary_APIC_clock(v
local_irq_enable();
}
-void __init disable_APIC_timer(void)
+void __devinit disable_APIC_timer(void)
{
if (using_apic_timer) {
unsigned long v;
Index: linux-2.6.9-rc3-mm3/arch/i386/kernel/io_apic.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/kernel/io_apic.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 io_apic.c
--- linux-2.6.9-rc3-mm3/arch/i386/kernel/io_apic.c 8 Oct 2004 10:56:07 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/kernel/io_apic.c 10 Oct 2004 18:31:21 -0000
@@ -574,9 +574,11 @@ static int balanced_irq(void *unused)
time_remaining = schedule_timeout(time_remaining);
if (time_after(jiffies,
prev_balance_time+balanced_irq_interval)) {
+ preempt_disable();
do_irq_balance();
prev_balance_time = jiffies;
time_remaining = balanced_irq_interval;
+ preempt_enable();
}
}
return 0;
Index: linux-2.6.9-rc3-mm3/arch/i386/kernel/irq.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/kernel/irq.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 irq.c
--- linux-2.6.9-rc3-mm3/arch/i386/kernel/irq.c 8 Oct 2004 10:56:08 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/kernel/irq.c 10 Oct 2004 20:18:02 -0000
@@ -14,6 +14,9 @@
#include <linux/seq_file.h>
#include <linux/interrupt.h>
#include <linux/kernel_stat.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
#include <asm/uaccess.h>
#include <asm/hardirq.h>
@@ -225,9 +228,8 @@ int show_interrupts(struct seq_file *p,
if (i == 0) {
seq_printf(p, " ");
- for (j=0; j<NR_CPUS; j++)
- if (cpu_online(j))
- seq_printf(p, "CPU%d ",j);
+ for_each_cpu(j)
+ seq_printf(p, "CPU%d ",j);
seq_putc(p, '\n');
}
@@ -240,9 +242,8 @@ int show_interrupts(struct seq_file *p,
#ifndef CONFIG_SMP
seq_printf(p, "%10u ", kstat_irqs(i));
#else
- for (j = 0; j < NR_CPUS; j++)
- if (cpu_online(j))
- seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
+ for_each_cpu(j)
+ seq_printf(p, "%10u ", kstat_cpu(j).irqs[i]);
#endif
seq_printf(p, " %14s", irq_desc[i].handler->typename);
seq_printf(p, " %s", action->name);
@@ -255,16 +256,13 @@ skip:
spin_unlock_irqrestore(&irq_desc[i].lock, flags);
} else if (i == NR_IRQS) {
seq_printf(p, "NMI: ");
- for (j = 0; j < NR_CPUS; j++)
- if (cpu_online(j))
- seq_printf(p, "%10u ", nmi_count(j));
+ for_each_cpu(j)
+ seq_printf(p, "%10u ", nmi_count(j));
seq_putc(p, '\n');
#ifdef CONFIG_X86_LOCAL_APIC
seq_printf(p, "LOC: ");
- for (j = 0; j < NR_CPUS; j++)
- if (cpu_online(j))
- seq_printf(p, "%10u ",
- irq_stat[j].apic_timer_irqs);
+ for_each_cpu(j)
+ seq_printf(p, "%10u ", irq_stat[j].apic_timer_irqs);
seq_putc(p, '\n');
#endif
seq_printf(p, "ERR: %10u\n", atomic_read(&irq_err_count));
@@ -274,3 +272,45 @@ skip:
}
return 0;
}
+
+#ifdef CONFIG_HOTPLUG_CPU
+#include <mach_apic.h>
+
+void fixup_irqs(cpumask_t map)
+{
+ unsigned int irq;
+ static int warned;
+
+ for (irq = 0; irq < NR_IRQS; irq++) {
+ cpumask_t mask;
+ if (irq == 2)
+ continue;
+
+ cpus_and(mask, irq_affinity[irq], map);
+ if (any_online_cpu(mask) == NR_CPUS) {
+ printk("Breaking affinity for irq %i\n", irq);
+ mask = map;
+ }
+ if (irq_desc[irq].handler->set_affinity)
+ irq_desc[irq].handler->set_affinity(irq, mask);
+ else if (irq_desc[irq].action && !(warned++))
+ printk("Cannot set affinity for irq %i\n", irq);
+ }
+
+#if 0
+ barrier();
+ /* Ingo Molnar says: "after the IO-APIC masks have been redirected
+ [note the nop - the interrupt-enable boundary on x86 is two
+ instructions from sti] - to flush out pending hardirqs and
+ IPIs. After this point nothing is supposed to reach this CPU." */
+ __asm__ __volatile__("sti; nop; cli");
+ barrier();
+#else
+ /* That doesn't seem sufficient. Give it 1ms. */
+ local_irq_enable();
+ mdelay(1);
+ local_irq_disable();
+#endif
+}
+#endif
+
Index: linux-2.6.9-rc3-mm3/arch/i386/kernel/msr.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/kernel/msr.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 msr.c
--- linux-2.6.9-rc3-mm3/arch/i386/kernel/msr.c 8 Oct 2004 10:56:08 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/kernel/msr.c 10 Oct 2004 18:31:21 -0000
@@ -260,7 +260,7 @@ static struct file_operations msr_fops =
.open = msr_open,
};
-static int msr_class_simple_device_add(int i)
+static int __devinit msr_class_simple_device_add(int i)
{
int err = 0;
struct class_device *class_err;
Index: linux-2.6.9-rc3-mm3/arch/i386/kernel/process.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/kernel/process.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 process.c
--- linux-2.6.9-rc3-mm3/arch/i386/kernel/process.c 8 Oct 2004 10:56:08 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/kernel/process.c 10 Oct 2004 18:31:21 -0000
@@ -13,6 +13,7 @@
#include <stdarg.h>
+#include <linux/cpu.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/fs.h>
@@ -54,6 +55,9 @@
#include <linux/irq.h>
#include <linux/err.h>
+#include <asm/tlbflush.h>
+#include <asm/cpu.h>
+
asmlinkage void ret_from_fork(void) __asm__("ret_from_fork");
int hlt_counter;
@@ -132,6 +136,34 @@ static void poll_idle (void)
}
}
+#ifdef CONFIG_HOTPLUG_CPU
+#include <asm/nmi.h>
+/* We don't actually take CPU down, just spin without interrupts. */
+static inline void play_dead(void)
+{
+ /* Ack it */
+ __get_cpu_var(cpu_state) = CPU_DEAD;
+
+ /* We shouldn't have to disable interrupts while dead, but
+ * some interrupts just don't seem to go away, and this makes
+ * it "work" for testing purposes. */
+ /* Death loop */
+ while (__get_cpu_var(cpu_state) != CPU_UP_PREPARE)
+ cpu_relax();
+
+ local_irq_disable();
+ __flush_tlb_all();
+ cpu_set(smp_processor_id(), cpu_online_map);
+ enable_APIC_timer();
+ local_irq_enable();
+}
+#else
+static inline void play_dead(void)
+{
+ BUG();
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
/*
* The idle thread. There's no useful work to be
* done, so just try to conserve power and have a
@@ -155,6 +187,8 @@ void cpu_idle (void)
if (!idle)
idle = default_idle;
+ if (cpu_is_offline(smp_processor_id()))
+ play_dead();
irq_stat[smp_processor_id()].idle_timestamp = jiffies;
idle();
rcu_read_unlock();
Index: linux-2.6.9-rc3-mm3/arch/i386/kernel/smp.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/kernel/smp.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 smp.c
--- linux-2.6.9-rc3-mm3/arch/i386/kernel/smp.c 8 Oct 2004 10:56:08 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/kernel/smp.c 10 Oct 2004 18:31:21 -0000
@@ -19,6 +19,7 @@
#include <linux/mc146818rtc.h>
#include <linux/cache.h>
#include <linux/interrupt.h>
+#include <linux/cpu.h>
#include <asm/mtrr.h>
#include <asm/tlbflush.h>
@@ -166,7 +167,7 @@ void send_IPI_mask_bitmask(cpumask_t cpu
unsigned long flags;
local_irq_save(flags);
-
+ WARN_ON(mask & ~cpus_addr(cpu_online_map)[0]);
/*
* Wait for idle.
*/
@@ -351,21 +352,21 @@ out:
static void flush_tlb_others(cpumask_t cpumask, struct mm_struct *mm,
unsigned long va)
{
- cpumask_t tmp;
/*
* A couple of (to be removed) sanity checks:
*
- * - we do not send IPIs to not-yet booted CPUs.
* - current CPU must not be in mask
* - mask must exist :)
*/
BUG_ON(cpus_empty(cpumask));
-
- cpus_and(tmp, cpumask, cpu_online_map);
- BUG_ON(!cpus_equal(cpumask, tmp));
BUG_ON(cpu_isset(smp_processor_id(), cpumask));
BUG_ON(!mm);
+ /* If a CPU which we ran on has gone down, OK. */
+ cpus_and(cpumask, cpumask, cpu_online_map);
+ if (cpus_empty(cpumask))
+ return;
+
/*
* i'm not happy about this global shared spinlock in the
* MM hot path, but we'll see how contended it is.
@@ -490,6 +491,7 @@ void smp_send_nmi_allbutself(void)
*/
void smp_send_reschedule(int cpu)
{
+ WARN_ON(cpu_is_offline(cpu));
send_IPI_mask(cpumask_of_cpu(cpu), RESCHEDULE_VECTOR);
}
@@ -535,10 +537,16 @@ int smp_call_function (void (*func) (voi
*/
{
struct call_data_struct data;
- int cpus = num_online_cpus()-1;
+ int cpus;
- if (!cpus)
+ /* Holding any lock stops cpus from going down. */
+ spin_lock(&call_lock);
+ cpus = num_online_cpus()-1;
+
+ if (!cpus) {
+ spin_unlock(&call_lock);
return 0;
+ }
/* Can deadlock when called with interrupts disabled */
WARN_ON(irqs_disabled());
@@ -550,7 +558,6 @@ int smp_call_function (void (*func) (voi
if (wait)
atomic_set(&data.finished, 0);
- spin_lock(&call_lock);
call_data = &data;
mb();
Index: linux-2.6.9-rc3-mm3/arch/i386/kernel/smpboot.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/kernel/smpboot.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 smpboot.c
--- linux-2.6.9-rc3-mm3/arch/i386/kernel/smpboot.c 8 Oct 2004 10:56:08 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/kernel/smpboot.c 10 Oct 2004 20:15:58 -0000
@@ -44,6 +44,9 @@
#include <linux/smp_lock.h>
#include <linux/irq.h>
#include <linux/bootmem.h>
+#include <linux/notifier.h>
+#include <linux/cpu.h>
+#include <linux/percpu.h>
#include <linux/delay.h>
#include <linux/mc146818rtc.h>
@@ -88,6 +91,9 @@ extern unsigned char trampoline_end [];
static unsigned char *trampoline_base;
static int trampoline_exec;
+/* State of each CPU. */
+DEFINE_PER_CPU(int, cpu_state) = { 0 };
+
/*
* Currently trivial. Write the real->protected mode
* bootstrap into the page concerned. The caller
@@ -1094,6 +1100,9 @@ static void __init smp_boot_cpus(unsigne
who understands all this stuff should rewrite it properly. --RR 15/Jul/02 */
void __init smp_prepare_cpus(unsigned int max_cpus)
{
+ smp_commenced_mask = cpumask_of_cpu(0);
+ cpu_callin_map = cpumask_of_cpu(0);
+ mb();
smp_boot_cpus(max_cpus);
}
@@ -1103,20 +1112,99 @@ void __devinit smp_prepare_boot_cpu(void
cpu_set(smp_processor_id(), cpu_callout_map);
}
-int __devinit __cpu_up(unsigned int cpu)
+#ifdef CONFIG_HOTPLUG_CPU
+
+/* must be called with the cpucontrol mutex held */
+static int __devinit cpu_enable(unsigned int cpu)
{
- /* This only works at boot for x86. See "rewrite" above. */
- if (cpu_isset(cpu, smp_commenced_mask)) {
- local_irq_enable();
- return -ENOSYS;
+ /* get the target out of its holding state */
+ per_cpu(cpu_state, cpu) = CPU_UP_PREPARE;
+ wmb();
+
+ /* wait for the processor to ack it. timeout? */
+ while (!cpu_online(cpu))
+ cpu_relax();
+
+ fixup_irqs(cpu_online_map);
+ /* counter the disable in fixup_irqs() */
+ local_irq_enable();
+ return 0;
+}
+
+int __cpu_disable(void)
+{
+ cpumask_t map = cpu_online_map;
+ int cpu = smp_processor_id();
+
+ /*
+ * Perhaps use cpufreq to drop frequency, but that could go
+ * into generic code.
+ *
+ * We won't take down the boot processor on i386 due to some
+ * interrupts only being able to be serviced by the BSP.
+ * Especially so if we're not using an IOAPIC -zwane
+ */
+ if (cpu == 0)
+ return -EBUSY;
+
+ /* We enable the timer again on the exit path of the death loop */
+ disable_APIC_timer();
+ /* Allow any queued timer interrupts to get serviced */
+ local_irq_enable();
+ mdelay(1);
+ local_irq_disable();
+
+ cpu_clear(cpu, map);
+ fixup_irqs(map);
+ /* It's now safe to remove this processor from the online map */
+ cpu_clear(cpu, cpu_online_map);
+ return 0;
+}
+
+void __cpu_die(unsigned int cpu)
+{
+ /* We don't do anything here: idle task is faking death itself. */
+ unsigned int i;
+
+ for (i = 0; i < 10; i++) {
+ /* They ack this in play_dead by setting CPU_DEAD */
+ if (per_cpu(cpu_state, cpu) == CPU_DEAD)
+ return;
+ current->state = TASK_UNINTERRUPTIBLE;
+ schedule_timeout(HZ/10);
}
+ printk(KERN_ERR "CPU %u didn't die...\n", cpu);
+}
+#else /* ... !CONFIG_HOTPLUG_CPU */
+int __cpu_disable(void)
+{
+ return -ENOSYS;
+}
+void __cpu_die(unsigned int cpu)
+{
+ /* We said "no" in __cpu_disable */
+ BUG();
+}
+#endif /* CONFIG_HOTPLUG_CPU */
+
+int __devinit __cpu_up(unsigned int cpu)
+{
/* In case one didn't come up */
if (!cpu_isset(cpu, cpu_callin_map)) {
+ printk(KERN_DEBUG "skipping cpu%d, didn't come online\n", cpu);
local_irq_enable();
return -EIO;
}
+#ifdef CONFIG_HOTPLUG_CPU
+ /* Already up, and in cpu_quiescent now? */
+ if (cpu_isset(cpu, smp_commenced_mask)) {
+ cpu_enable(cpu);
+ return 0;
+ }
+#endif
+
local_irq_enable();
/* Unleash the CPU! */
cpu_set(cpu, smp_commenced_mask);
Index: linux-2.6.9-rc3-mm3/arch/i386/kernel/traps.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/i386/kernel/traps.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 traps.c
--- linux-2.6.9-rc3-mm3/arch/i386/kernel/traps.c 8 Oct 2004 10:56:08 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/i386/kernel/traps.c 10 Oct 2004 18:31:21 -0000
@@ -692,6 +692,14 @@ asmlinkage void do_nmi(struct pt_regs *
nmi_enter();
cpu = smp_processor_id();
+
+#ifdef CONFIG_HOTPLUG_CPU
+ if (!cpu_online(cpu)) {
+ nmi_exit();
+ return;
+ }
+#endif
+
++nmi_count(cpu);
if (!nmi_callback(regs, cpu))
Index: linux-2.6.9-rc3-mm3/arch/ia64/kernel/smpboot.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/ia64/kernel/smpboot.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 smpboot.c
--- linux-2.6.9-rc3-mm3/arch/ia64/kernel/smpboot.c 8 Oct 2004 10:55:28 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/ia64/kernel/smpboot.c 10 Oct 2004 18:31:21 -0000
@@ -591,9 +591,10 @@ int __cpu_disable(void)
if (cpu == 0)
return -EBUSY;
+ cpu_clear(cpu, cpu_online_map);
fixup_irqs();
local_flush_tlb_all();
- printk ("Disabled cpu %u\n", smp_processor_id());
+ printk("Disabled cpu %u\n", cpu);
return 0;
}
Index: linux-2.6.9-rc3-mm3/arch/ppc64/kernel/smp.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/ppc64/kernel/smp.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 smp.c
--- linux-2.6.9-rc3-mm3/arch/ppc64/kernel/smp.c 8 Oct 2004 10:56:09 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/ppc64/kernel/smp.c 10 Oct 2004 18:31:21 -0000
@@ -273,11 +273,13 @@ int __cpu_disable(void)
{
/* FIXME: go put this in a header somewhere */
extern void xics_migrate_irqs_away(void);
+ int cpu = smp_processor_id();
+ cpu_clear(cpu, cpu_online_map);
systemcfg->processorCount--;
/*fix boot_cpuid here*/
- if (smp_processor_id() == boot_cpuid)
+ if (cpu == boot_cpuid)
boot_cpuid = any_online_cpu(cpu_online_map);
/* FIXME: abstract this to not be platform specific later on */
Index: linux-2.6.9-rc3-mm3/arch/s390/kernel/smp.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/arch/s390/kernel/smp.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 smp.c
--- linux-2.6.9-rc3-mm3/arch/s390/kernel/smp.c 8 Oct 2004 10:55:45 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/arch/s390/kernel/smp.c 10 Oct 2004 18:31:21 -0000
@@ -688,13 +688,15 @@ __cpu_disable(void)
{
unsigned long flags;
ec_creg_mask_parms cr_parms;
+ int cpu = smp_processor_id();
spin_lock_irqsave(&smp_reserve_lock, flags);
- if (smp_cpu_reserved[smp_processor_id()] != 0) {
+ if (smp_cpu_reserved[cpu] != 0) {
spin_unlock_irqrestore(&smp_reserve_lock, flags);
return -EBUSY;
}
+ cpu_clear(cpu, cpu_online_map);
/* disable all external interrupts */
cr_parms.start_ctl = 0;
Index: linux-2.6.9-rc3-mm3/include/asm-i386/cpu.h
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/include/asm-i386/cpu.h,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 cpu.h
--- linux-2.6.9-rc3-mm3/include/asm-i386/cpu.h 8 Oct 2004 10:53:52 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/include/asm-i386/cpu.h 10 Oct 2004 18:31:21 -0000
@@ -5,6 +5,7 @@
#include <linux/cpu.h>
#include <linux/topology.h>
#include <linux/nodemask.h>
+#include <linux/percpu.h>
#include <asm/node.h>
@@ -26,4 +27,5 @@ static inline int arch_register_cpu(int
return register_cpu(&cpu_devices[num].cpu, num, parent);
}
+DECLARE_PER_CPU(int, cpu_state);
#endif /* _ASM_I386_CPU_H_ */
Index: linux-2.6.9-rc3-mm3/include/asm-i386/irq.h
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/include/asm-i386/irq.h,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 irq.h
--- linux-2.6.9-rc3-mm3/include/asm-i386/irq.h 8 Oct 2004 10:53:52 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/include/asm-i386/irq.h 10 Oct 2004 20:34:06 -0000
@@ -34,4 +34,8 @@ extern void release_vm86_irqs(struct tas
# define irq_ctx_init(cpu) do { } while (0)
#endif
+#ifdef CONFIG_HOTPLUG_CPU
+extern void fixup_irqs(cpumask_t map);
+#endif
+
#endif /* _ASM_IRQ_H */
Index: linux-2.6.9-rc3-mm3/include/asm-i386/smp.h
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/include/asm-i386/smp.h,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 smp.h
--- linux-2.6.9-rc3-mm3/include/asm-i386/smp.h 8 Oct 2004 10:53:52 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/include/asm-i386/smp.h 10 Oct 2004 18:31:21 -0000
@@ -85,6 +85,9 @@ static __inline int logical_smp_processo
}
#endif
+
+extern int __cpu_disable(void);
+extern void __cpu_die(unsigned int cpu);
#endif /* !__ASSEMBLY__ */
#define NO_PROC_ID 0xFF /* No processor magic marker */
Index: linux-2.6.9-rc3-mm3/kernel/cpu.c
===================================================================
RCS file: /home/cvsroot/linux-2.6.9-rc3-mm3/kernel/cpu.c,v
retrieving revision 1.1.1.1
diff -u -p -B -r1.1.1.1 cpu.c
--- linux-2.6.9-rc3-mm3/kernel/cpu.c 8 Oct 2004 10:56:10 -0000 1.1.1.1
+++ linux-2.6.9-rc3-mm3/kernel/cpu.c 10 Oct 2004 18:31:21 -0000
@@ -62,19 +62,15 @@ static int take_cpu_down(void *unused)
{
int err;
- /* Take offline: makes arch_cpu_down somewhat easier. */
- cpu_clear(smp_processor_id(), cpu_online_map);
-
/* Ensure this CPU doesn't handle any more interrupts. */
err = __cpu_disable();
if (err < 0)
- cpu_set(smp_processor_id(), cpu_online_map);
- else
- /* Force idle task to run as soon as we yield: it should
- immediately notice cpu is offline and die quickly. */
- sched_idle_next();
+ return err;
- return err;
+ /* Force idle task to run as soon as we yield: it should
+ immediately notice cpu is offline and die quickly. */
+ sched_idle_next();
+ return 0;
}
int cpu_down(unsigned int cpu)
On Mon, 2004-10-11 at 03:19, Zwane Mwaikambo wrote:
> Hi Andrew,
> Find attached the i386 cpu hotplug patch updated for Ingo's latest
> round of goodies. In order to avoid dumping cpu hotplug code into
> kernel/irq/* i dropped the cpu_online check in do_IRQ() by modifying
> fixup_irqs(). The difference being that on cpu offline, fixup_irqs() is
> called before we clear the cpu from cpu_online_map and a long delay in
> order to ensure that we never have any queued external interrupts on the
> APICs. Due to my usual test victims being in boxes a continent away this
> hasn't been tested, but i'll cover bug reports (nudge, Nathan! ;)
Had to apply the patch to 2.6.9-rc4-mm1 (2.6.9-rc3-mm3 doesn't detect my
scsi controller). Tested on a dual Pentium 3. Simple offline/online
tests seem ok, except I see these warnings when taking a cpu down:
using smp_processor_id() in preemptible code: bash/3436
[<c0106f37>] dump_stack+0x17/0x20
[<c011a087>] smp_processor_id+0x87/0xa0
[<c0134d54>] cpu_down+0x134/0x240
[<c02770d9>] store_online+0x39/0x70
[<c0274487>] sysdev_store+0x37/0x50
[<c019339e>] flush_write_buffer+0x2e/0x40
[<c0193427>] sysfs_write_file+0x77/0x90
[<c015aa20>] vfs_write+0xe0/0x120
[<c015ab0d>] sys_write+0x3d/0x70
[<c0106123>] syscall_call+0x7/0xb
using smp_processor_id() in preemptible code: ksoftirqd/1/5233
[<c0106f37>] dump_stack+0x17/0x20
[<c011a087>] smp_processor_id+0x87/0xa0
[<c0124128>] ksoftirqd+0x68/0x140
[<c0133326>] kthread+0x96/0xe0
[<c0104275>] kernel_thread_helper+0x5/0x10
Under load (unpacking a kernel source tree while continuous
online/offline of a cpu) I got a panic within a couple of minutes:
Unable to handle kernel NULL pointer dereference at virtual address 00000004
printing eip:
c0145703
*pde = 00000000
Oops: 0000 [#1]
PREEMPT SMP
Modules linked in:
CPU: 1
EIP: 0060:[<c0145703>] Not tainted VLI
EFLAGS: 00010082 (2.6.9-rc4-mm1i386cpuhp)
EIP is at kmem_cache_free+0x33/0x70
eax: cba2cd98 ebx: 00000000 ecx: 00000000 edx: cba2cd98
esi: c1561ac0 edi: cba2cd98 ebp: c058be8c esp: c058be7c
ds: 007b es: 007b ss: 0068
Process swapper (pid: 0, threadinfo=c058b000 task=dff88540)
Stack: 00000082 c1559920 00001000 cba2cd9c c058bea4 c013e491 00000000 cf4abee0
00001000 c015f050 c058beb0 c015f92c cf4abee0 c058beb8 c015fbac c058bec4
c015f07d cf4abee0 c058beec c0160819 c0271a48 c0127c11 00000001 00000002
Call Trace:
[<c0106f0a>] show_stack+0x7a/0x90
[<c0107096>] show_registers+0x156/0x1d0
[<c01072b4>] die+0xf4/0x180
[<c0116bd7>] do_page_fault+0x457/0x66d
[<c0106b8d>] error_code+0x2d/0x38
[<c013e491>] mempool_free+0x81/0x90
[<c015f92c>] bio_destructor+0x3c/0x60
[<c015fbac>] bio_put+0x2c/0x40
[<c015f07d>] end_bio_bh_io_sync+0x2d/0x60
[<c0160819>] bio_endio+0x59/0x90
[<c027c578>] __end_that_request_first+0x188/0x250
[<c029db14>] __ide_end_request+0x54/0x150
[<c029dc68>] ide_end_request+0x58/0xc0
[<c02a3fe1>] task_end_request+0x31/0x70
[<c02a418b>] task_out_intr+0x7b/0x100
[<c029f6cd>] ide_intr+0xbd/0x160
[<c0139d44>] handle_IRQ_event+0x34/0x70
[<c0139e6c>] __do_IRQ+0xec/0x170
[<c0108570>] do_IRQ+0x60/0xa0
=======================
[<c0106a90>] common_interrupt+0x18/0x20
[<00000000>] 0x0
[<dff84fbc>] 0xdff84fbc
Code: f8 89 c6 89 5d f4 89 7d fc 9c 8f 45 f0 fa 89 d7 e8 13 49 fd ff 8b 1c 86 e8 6b ea ff ff 8b 4d 04 89 fa 89 f0 e8 2f f3 ff ff 89 c7 <8b> 43 04 39 03 73 20 f0 ff 86 c4 00 00 00 8b 03 89 7c 83 10 ff
<0>Kernel panic - not syncing: Fatal exception in interrupt
I fixed up the warning in cpu_down with the following patch and now am
running with that + 2.6.9-rc4-mm1 + your patch while doing continuous
online/offline and make -j8. It's been running for about 45 minutes and
I haven't seen the panic yet, although I'm at a loss to explain why the
change would fix it. Will let it run overnight and report back...
Nathan
--
Fix (harmless?) smp_processor_id() usage in preemptible section of
cpu_down.
Signed-off-by: Nathan Lynch <[email protected]>
---
2.6.9-rc4-mm1-nathanl/kernel/cpu.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletion(-)
diff -puN kernel/cpu.c~cpu_down-fix-smp_processor_id-warning kernel/cpu.c
--- 2.6.9-rc4-mm1/kernel/cpu.c~cpu_down-fix-smp_processor_id-warning 2004-10-11 23:28:47.000000000 -0500
+++ 2.6.9-rc4-mm1-nathanl/kernel/cpu.c 2004-10-11 23:34:36.000000000 -0500
@@ -129,7 +129,8 @@ int cpu_down(unsigned int cpu)
__cpu_die(cpu);
/* Move it here so it can run. */
- kthread_bind(p, smp_processor_id());
+ kthread_bind(p, get_cpu());
+ put_cpu();
/* CPU is completely dead: tell everyone. Too late to complain. */
if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
_
* Nathan Lynch <[email protected]> wrote:
> I fixed up the warning in cpu_down with the following patch and now am
> running with that + 2.6.9-rc4-mm1 + your patch while doing continuous
> online/offline and make -j8. It's been running for about 45 minutes
> and I haven't seen the panic yet, although I'm at a loss to explain
> why the change would fix it. Will let it run overnight and report
> back...
> /* Move it here so it can run. */
> - kthread_bind(p, smp_processor_id());
> + kthread_bind(p, get_cpu());
> + put_cpu();
> /* CPU is completely dead: tell everyone. Too late to complain. */
> if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
hm, is there any assurance that smp_processor_id() == cpu?
but i agree, this fix shouldnt impact the bio-destruct slab crash you
were seeing.
Ingo
On Mon, 2004-10-11 at 22:59, Nathan Lynch wrote:
> On Mon, 2004-10-11 at 03:19, Zwane Mwaikambo wrote:
> > Hi Andrew,
> > Find attached the i386 cpu hotplug patch updated for Ingo's latest
> > round of goodies. In order to avoid dumping cpu hotplug code into
> > kernel/irq/* i dropped the cpu_online check in do_IRQ() by modifying
> > fixup_irqs(). The difference being that on cpu offline, fixup_irqs() is
> > called before we clear the cpu from cpu_online_map and a long delay in
> > order to ensure that we never have any queued external interrupts on the
> > APICs. Due to my usual test victims being in boxes a continent away this
> > hasn't been tested, but i'll cover bug reports (nudge, Nathan! ;)
>
> Had to apply the patch to 2.6.9-rc4-mm1 (2.6.9-rc3-mm3 doesn't detect my
> scsi controller). Tested on a dual Pentium 3. Simple offline/online
> tests seem ok, except I see these warnings when taking a cpu down:
>
> using smp_processor_id() in preemptible code: bash/3436
> [<c0106f37>] dump_stack+0x17/0x20
> [<c011a087>] smp_processor_id+0x87/0xa0
> [<c0134d54>] cpu_down+0x134/0x240
> [<c02770d9>] store_online+0x39/0x70
> [<c0274487>] sysdev_store+0x37/0x50
> [<c019339e>] flush_write_buffer+0x2e/0x40
> [<c0193427>] sysfs_write_file+0x77/0x90
> [<c015aa20>] vfs_write+0xe0/0x120
> [<c015ab0d>] sys_write+0x3d/0x70
> [<c0106123>] syscall_call+0x7/0xb
I think this warning is likely bogus:
/* Move it here so it can run. */
kthread_bind(p, smp_processor_id());
That just makes sure that the thread can get cleaned up somewhere on
some active cpu. The only problem would be if the cpu that the thread
was bound to also went down. But, I think that's prevented by the big
cpu hotplug semaphore. (the "down"ing CPU can't be "down"ed in the
process of "down"ing :)
> diff -puN kernel/cpu.c~cpu_down-fix-smp_processor_id-warning kernel/cpu.c
> --- 2.6.9-rc4-mm1/kernel/cpu.c~cpu_down-fix-smp_processor_id-warning 2004-10-11 23:28:47.000000000 -0500
> +++ 2.6.9-rc4-mm1-nathanl/kernel/cpu.c 2004-10-11 23:34:36.000000000 -0500
> @@ -129,7 +129,8 @@ int cpu_down(unsigned int cpu)
> __cpu_die(cpu);
>
> /* Move it here so it can run. */
> - kthread_bind(p, smp_processor_id());
> + kthread_bind(p, get_cpu());
> + put_cpu();
This doesn't do much more than suppress the warning. If there was some
kind race there before, then it's still there but is now hidden.
-- Dave
On Tue, 2004-10-12 at 01:04, Ingo Molnar wrote:
> * Nathan Lynch <[email protected]> wrote:
>
> > I fixed up the warning in cpu_down with the following patch and now am
> > running with that + 2.6.9-rc4-mm1 + your patch while doing continuous
> > online/offline and make -j8. It's been running for about 45 minutes
> > and I haven't seen the panic yet, although I'm at a loss to explain
> > why the change would fix it. Will let it run overnight and report
> > back...
>
> > /* Move it here so it can run. */
> > - kthread_bind(p, smp_processor_id());
> > + kthread_bind(p, get_cpu());
> > + put_cpu();
>
> > /* CPU is completely dead: tell everyone. Too late to complain. */
> > if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
>
> hm, is there any assurance that smp_processor_id() == cpu?
Actually, cpu != smp_processor_id(). cpu is the processor we have just
taken down at that point; we want the kthread to run on some other cpu.
Nathan
On Tue, 12 Oct 2004, Nathan Lynch wrote:
> On Tue, 2004-10-12 at 01:04, Ingo Molnar wrote:
> > * Nathan Lynch <[email protected]> wrote:
> >
> > > I fixed up the warning in cpu_down with the following patch and now am
> > > running with that + 2.6.9-rc4-mm1 + your patch while doing continuous
> > > online/offline and make -j8. It's been running for about 45 minutes
> > > and I haven't seen the panic yet, although I'm at a loss to explain
> > > why the change would fix it. Will let it run overnight and report
> > > back...
> >
> > > /* Move it here so it can run. */
> > > - kthread_bind(p, smp_processor_id());
> > > + kthread_bind(p, get_cpu());
> > > + put_cpu();
> >
> > > /* CPU is completely dead: tell everyone. Too late to complain. */
> > > if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
> >
> > hm, is there any assurance that smp_processor_id() == cpu?
>
> Actually, cpu != smp_processor_id(). cpu is the processor we have just
> taken down at that point; we want the kthread to run on some other cpu.
Nathan, thanks for doing that testing, the warning does indeed look to be
a false positive. Looking at the code again, i realised that there might
also be cases where someone does the following;
preempt_disable();
cpu = smp_processor_id();
...
preempt_enable();
...
mod_local_cpu_variable[cpu];
So cached values of smp_processor_id() might also be a problem, although i
haven't found any cases, but maybe that's just being overly paranoid =)
On Tue, 12 Oct 2004, Nathan Lynch wrote:
> Unable to handle kernel NULL pointer dereference at virtual address 00000004
> printing eip:
> c0145703
> *pde = 00000000
> Oops: 0000 [#1]
> PREEMPT SMP
> Modules linked in:
> CPU: 1
Ok, cpu1 took an interrupt and exploded, perhaps put a printk in
show_regs() to say whether it was offline, an interrupt must have snuck in
whilst it was offline.
> [<c029f6cd>] ide_intr+0xbd/0x160
> [<c0139d44>] handle_IRQ_event+0x34/0x70
> [<c0139e6c>] __do_IRQ+0xec/0x170
> [<c0108570>] do_IRQ+0x60/0xa0
Thanks,
Zwane
Hi!
> +#ifdef CONFIG_HOTPLUG_CPU
> +#include <asm/nmi.h>
> +/* We don't actually take CPU down, just spin without interrupts. */
> +static inline void play_dead(void)
> +{
> + /* Ack it */
> + __get_cpu_var(cpu_state) = CPU_DEAD;
> +
> + /* We shouldn't have to disable interrupts while dead, but
> + * some interrupts just don't seem to go away, and this makes
> + * it "work" for testing purposes. */
> + /* Death loop */
> + while (__get_cpu_var(cpu_state) != CPU_UP_PREPARE)
> + cpu_relax();
> +
> + local_irq_disable();
> + __flush_tlb_all();
> + cpu_set(smp_processor_id(), cpu_online_map);
> + enable_APIC_timer();
> + local_irq_enable();
> +}
> +#else
Having real implementation of this one would be very welcome for
suspend-to-{RAM,disk} on smp machines....
Are there really no i386 machines whose hardware supports hotplug?
Pavel
--
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!
On Mon, 18 Oct 2004, Pavel Machek wrote:
> Having real implementation of this one would be very welcome for
> suspend-to-{RAM,disk} on smp machines....
I actually started working on that already but progress got hindered by
non technical related issues, i hope to get back to it very soon. This is
indeed handy for P4 HT type laptops.
> Are there really no i386 machines whose hardware supports hotplug?
There are i386 systems which do support hardware hotplug, mostly addition
of processors. I haven't personally worked with any but have been in
contact with people who are interested in the code for that specific
reason.
Regards,
Zwane