[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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Andi Kleen <ak@suse.de>
diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index 7af9cb3..27e95e7 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -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 @@
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 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 @@
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 @@
#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);