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Commit bb81a09e authored by Andrew Morton's avatar Andrew Morton Committed by Andi Kleen
Browse files

[PATCH] x86: all cpu backtrace 



When a spinlock lockup occurs, arrange for the NMI code to emit an all-cpu
backtrace, so we get to see which CPU is holding the lock, and where.

Cc: Andi Kleen <ak@muc.de>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent e5e3a042

arch/i386/kernel/nmi.c

+26 −0
Original line number Diff line number Diff line
@@ -22,6 +22,7 @@ 
#include <linux/percpu.h>

#include <linux/dmi.h>

#include <linux/kprobes.h>

#include <linux/cpumask.h>



#include <asm/smp.h>

#include <asm/nmi.h>
@@ -42,6 +43,8 @@ int nmi_watchdog_enabled; 
static DEFINE_PER_CPU(unsigned long, perfctr_nmi_owner);

static DEFINE_PER_CPU(unsigned long, evntsel_nmi_owner[3]);



static cpumask_t backtrace_mask = CPU_MASK_NONE;



/* this number is calculated from Intel's MSR_P4_CRU_ESCR5 register and it's

 * offset from MSR_P4_BSU_ESCR0.  It will be the max for all platforms (for now)

 */
@@ -907,6 +910,16 @@ __kprobes int nmi_watchdog_tick(struct pt_regs * regs, unsigned reason) 
		touched = 1;

	}



	if (cpu_isset(cpu, backtrace_mask)) {

		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */



		spin_lock(&lock);

		printk("NMI backtrace for cpu %d\n", cpu);

		dump_stack();

		spin_unlock(&lock);

		cpu_clear(cpu, backtrace_mask);

	}



	sum = per_cpu(irq_stat, cpu).apic_timer_irqs;



	/* if the apic timer isn't firing, this cpu isn't doing much */
@@ -1033,6 +1046,19 @@ int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file, 


#endif



void __trigger_all_cpu_backtrace(void)

{

	int i;



	backtrace_mask = cpu_online_map;

	/* Wait for up to 10 seconds for all CPUs to do the backtrace */

	for (i = 0; i < 10 * 1000; i++) {

		if (cpus_empty(backtrace_mask))

			break;

		mdelay(1);

	}

}



EXPORT_SYMBOL(nmi_active);

EXPORT_SYMBOL(nmi_watchdog);

EXPORT_SYMBOL(avail_to_resrv_perfctr_nmi);

arch/x86_64/kernel/nmi.c

+28 −1
Original line number Diff line number Diff line
@@ -12,14 +12,15 @@ 
 *  Mikael Pettersson	: PM converted to driver model. Disable/enable API.

 */



#include <linux/nmi.h>

#include <linux/mm.h>

#include <linux/delay.h>

#include <linux/interrupt.h>

#include <linux/module.h>

#include <linux/sysdev.h>

#include <linux/nmi.h>

#include <linux/sysctl.h>

#include <linux/kprobes.h>

#include <linux/cpumask.h>



#include <asm/smp.h>

#include <asm/nmi.h>
@@ -41,6 +42,8 @@ int panic_on_unrecovered_nmi; 
static DEFINE_PER_CPU(unsigned, perfctr_nmi_owner);

static DEFINE_PER_CPU(unsigned, evntsel_nmi_owner[2]);



static cpumask_t backtrace_mask = CPU_MASK_NONE;



/* this number is calculated from Intel's MSR_P4_CRU_ESCR5 register and it's

 * offset from MSR_P4_BSU_ESCR0.  It will be the max for all platforms (for now)

 */
@@ -782,6 +785,7 @@ int __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason) 
{

	int sum;

	int touched = 0;

	int cpu = smp_processor_id();

	struct nmi_watchdog_ctlblk *wd = &__get_cpu_var(nmi_watchdog_ctlblk);

	u64 dummy;

	int rc=0;
@@ -799,6 +803,16 @@ int __kprobes nmi_watchdog_tick(struct pt_regs * regs, unsigned reason) 
		touched = 1;

	}



	if (cpu_isset(cpu, backtrace_mask)) {

		static DEFINE_SPINLOCK(lock);	/* Serialise the printks */



		spin_lock(&lock);

		printk("NMI backtrace for cpu %d\n", cpu);

		dump_stack();

		spin_unlock(&lock);

		cpu_clear(cpu, backtrace_mask);

	}



#ifdef CONFIG_X86_MCE

	/* Could check oops_in_progress here too, but it's safer

	   not too */
@@ -931,6 +945,19 @@ int proc_nmi_enabled(struct ctl_table *table, int write, struct file *file, 


#endif



void __trigger_all_cpu_backtrace(void)

{

	int i;



	backtrace_mask = cpu_online_map;

	/* Wait for up to 10 seconds for all CPUs to do the backtrace */

	for (i = 0; i < 10 * 1000; i++) {

		if (cpus_empty(backtrace_mask))

			break;

		mdelay(1);

	}

}



EXPORT_SYMBOL(nmi_active);

EXPORT_SYMBOL(nmi_watchdog);

EXPORT_SYMBOL(avail_to_resrv_perfctr_nmi);

include/asm-i386/nmi.h

+8 −0
Original line number Diff line number Diff line
@@ -5,6 +5,9 @@ 
#define ASM_NMI_H



#include <linux/pm.h>

#include <asm/irq.h>



#ifdef ARCH_HAS_NMI_WATCHDOG



/**

 * do_nmi_callback
@@ -42,4 +45,9 @@ extern int proc_nmi_enabled(struct ctl_table *, int , struct file *, 
			void __user *, size_t *, loff_t *);

extern int unknown_nmi_panic;



void __trigger_all_cpu_backtrace(void);

#define trigger_all_cpu_backtrace() __trigger_all_cpu_backtrace()



#endif



#endif /* ASM_NMI_H */

include/asm-x86_64/nmi.h

+3 −0
Original line number Diff line number Diff line
@@ -77,4 +77,7 @@ extern int proc_nmi_enabled(struct ctl_table *, int , struct file *, 


extern int unknown_nmi_panic;



void __trigger_all_cpu_backtrace(void);

#define trigger_all_cpu_backtrace() __trigger_all_cpu_backtrace()



#endif /* ASM_NMI_H */

include/linux/nmi.h

+5 −0
Original line number Diff line number Diff line
@@ -15,9 +15,14 @@ 
 * disables interrupts for a long time. This call is stateless.

 */

#ifdef ARCH_HAS_NMI_WATCHDOG

#include <asm/nmi.h>

extern void touch_nmi_watchdog(void);

#else

# define touch_nmi_watchdog() touch_softlockup_watchdog()

#endif



#ifndef trigger_all_cpu_backtrace

#define trigger_all_cpu_backtrace() do { } while (0)

#endif



#endif