diff options
| -rw-r--r-- | arch/powerpc/kernel/watchdog.c | 37 |
1 files changed, 31 insertions, 6 deletions
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index 23745af38d62..bfc27496fe7e 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -86,6 +86,7 @@ static DEFINE_PER_CPU(u64, wd_timer_tb); /* SMP checker bits */ static unsigned long __wd_smp_lock; static unsigned long __wd_reporting; +static unsigned long __wd_nmi_output; static cpumask_t wd_smp_cpus_pending; static cpumask_t wd_smp_cpus_stuck; static u64 wd_smp_last_reset_tb; @@ -154,6 +155,23 @@ static void wd_lockup_ipi(struct pt_regs *regs) else dump_stack(); + /* + * __wd_nmi_output must be set after we printk from NMI context. + * + * printk from NMI context defers printing to the console to irq_work. + * If that NMI was taken in some code that is hard-locked, then irqs + * are disabled so irq_work will never fire. That can result in the + * hard lockup messages being delayed (indefinitely, until something + * else kicks the console drivers). + * + * Setting __wd_nmi_output will cause another CPU to notice and kick + * the console drivers for us. + * + * xchg is not needed here (it could be a smp_mb and store), but xchg + * gives the memory ordering and atomicity required. + */ + xchg(&__wd_nmi_output, 1); + /* Do not panic from here because that can recurse into NMI IPI layer */ } @@ -227,12 +245,6 @@ static void watchdog_smp_panic(int cpu) cpumask_clear(&wd_smp_cpus_ipi); } - /* - * Force flush any remote buffers that might be stuck in IRQ context - * and therefore could not run their irq_work. - */ - printk_trigger_flush(); - if (hardlockup_panic) nmi_panic(NULL, "Hard LOCKUP"); @@ -337,6 +349,17 @@ static void watchdog_timer_interrupt(int cpu) if ((s64)(tb - wd_smp_last_reset_tb) >= (s64)wd_smp_panic_timeout_tb) watchdog_smp_panic(cpu); + + if (__wd_nmi_output && xchg(&__wd_nmi_output, 0)) { + /* + * Something has called printk from NMI context. It might be + * stuck, so this this triggers a flush that will get that + * printk output to the console. + * + * See wd_lockup_ipi. + */ + printk_trigger_flush(); + } } DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt) @@ -386,6 +409,8 @@ DEFINE_INTERRUPT_HANDLER_NMI(soft_nmi_interrupt) print_irqtrace_events(current); show_regs(regs); + xchg(&__wd_nmi_output, 1); // see wd_lockup_ipi + if (sysctl_hardlockup_all_cpu_backtrace) trigger_allbutself_cpu_backtrace(); |