x86: all cpu backtrace From: Andrew Morton 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 Cc: Ingo Molnar Cc: Badari Pulavarty Signed-off-by: Andrew Morton Signed-off-by: Andi Kleen --- arch/i386/kernel/nmi.c | 26 ++++++++++++++++++++++++++ arch/x86_64/kernel/nmi.c | 29 ++++++++++++++++++++++++++++- include/asm-i386/nmi.h | 3 +++ include/asm-x86_64/nmi.h | 3 +++ include/linux/nmi.h | 5 +++++ lib/spinlock_debug.c | 4 ++++ 6 files changed, 69 insertions(+), 1 deletion(-) Index: linux/arch/i386/kernel/nmi.c =================================================================== --- linux.orig/arch/i386/kernel/nmi.c +++ linux/arch/i386/kernel/nmi.c @@ -22,6 +22,7 @@ #include #include #include +#include #include #include @@ -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 p 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 *t #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); Index: linux/arch/x86_64/kernel/nmi.c =================================================================== --- linux.orig/arch/x86_64/kernel/nmi.c +++ linux/arch/x86_64/kernel/nmi.c @@ -12,14 +12,15 @@ * Mikael Pettersson : PM converted to driver model. Disable/enable API. */ +#include #include #include #include #include #include -#include #include #include +#include #include #include @@ -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 p { 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 p 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 *t #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); Index: linux/include/asm-i386/nmi.h =================================================================== --- linux.orig/include/asm-i386/nmi.h +++ linux/include/asm-i386/nmi.h @@ -42,4 +42,7 @@ extern int proc_nmi_enabled(struct ctl_t 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 /* ASM_NMI_H */ Index: linux/include/asm-x86_64/nmi.h =================================================================== --- linux.orig/include/asm-x86_64/nmi.h +++ linux/include/asm-x86_64/nmi.h @@ -77,4 +77,7 @@ extern int proc_nmi_enabled(struct ctl_t extern int unknown_nmi_panic; +void __trigger_all_cpu_backtrace(void); +#define trigger_all_cpu_backtrace() __trigger_all_cpu_backtrace() + #endif /* ASM_NMI_H */ Index: linux/include/linux/nmi.h =================================================================== --- linux.orig/include/linux/nmi.h +++ linux/include/linux/nmi.h @@ -15,9 +15,14 @@ * disables interrupts for a long time. This call is stateless. */ #ifdef ARCH_HAS_NMI_WATCHDOG +#include 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 Index: linux/lib/spinlock_debug.c =================================================================== --- linux.orig/lib/spinlock_debug.c +++ linux/lib/spinlock_debug.c @@ -7,6 +7,7 @@ */ #include +#include #include #include #include @@ -117,6 +118,9 @@ static void __spin_lock_debug(spinlock_t raw_smp_processor_id(), current->comm, current->pid, lock); dump_stack(); +#ifdef CONFIG_SMP + trigger_all_cpu_backtrace(); +#endif } } }