diff options
Diffstat (limited to 'arch/powerpc/kernel/watchdog.c')
| -rw-r--r-- | arch/powerpc/kernel/watchdog.c | 100 |
1 files changed, 48 insertions, 52 deletions
diff --git a/arch/powerpc/kernel/watchdog.c b/arch/powerpc/kernel/watchdog.c index 87da80ccced1..6256dc3b0087 100644 --- a/arch/powerpc/kernel/watchdog.c +++ b/arch/powerpc/kernel/watchdog.c @@ -6,6 +6,9 @@ * * This uses code from arch/sparc/kernel/nmi.c and kernel/watchdog.c */ + +#define pr_fmt(fmt) "watchdog: " fmt + #include <linux/kernel.h> #include <linux/param.h> #include <linux/init.h> @@ -26,15 +29,45 @@ #include <asm/paca.h> /* - * The watchdog has a simple timer that runs on each CPU, once per timer - * period. This is the heartbeat. + * The powerpc watchdog ensures that each CPU is able to service timers. + * The watchdog sets up a simple timer on each CPU to run once per timer + * period, and updates a per-cpu timestamp and a "pending" cpumask. This is + * the heartbeat. + * + * Then there are two systems to check that the heartbeat is still running. + * The local soft-NMI, and the SMP checker. + * + * The soft-NMI checker can detect lockups on the local CPU. When interrupts + * are disabled with local_irq_disable(), platforms that use soft-masking + * can leave hardware interrupts enabled and handle them with a masked + * interrupt handler. The masked handler can send the timer interrupt to the + * watchdog's soft_nmi_interrupt(), which appears to Linux as an NMI + * interrupt, and can be used to detect CPUs stuck with IRQs disabled. + * + * The soft-NMI checker will compare the heartbeat timestamp for this CPU + * with the current time, and take action if the difference exceeds the + * watchdog threshold. + * + * The limitation of the soft-NMI watchdog is that it does not work when + * interrupts are hard disabled or otherwise not being serviced. This is + * solved by also having a SMP watchdog where all CPUs check all other + * CPUs heartbeat. * - * Then there are checks to see if the heartbeat has not triggered on a CPU - * for the panic timeout period. Currently the watchdog only supports an - * SMP check, so the heartbeat only turns on when we have 2 or more CPUs. + * The SMP checker can detect lockups on other CPUs. A gobal "pending" + * cpumask is kept, containing all CPUs which enable the watchdog. Each + * CPU clears their pending bit in their heartbeat timer. When the bitmask + * becomes empty, the last CPU to clear its pending bit updates a global + * timestamp and refills the pending bitmask. * - * This is not an NMI watchdog, but Linux uses that name for a generic - * watchdog in some cases, so NMI gets used in some places. + * In the heartbeat timer, if any CPU notices that the global timestamp has + * not been updated for a period exceeding the watchdog threshold, then it + * means the CPU(s) with their bit still set in the pending mask have had + * their heartbeat stop, and action is taken. + * + * Some platforms implement true NMI IPIs, which can by used by the SMP + * watchdog to detect an unresponsive CPU and pull it out of its stuck + * state with the NMI IPI, to get crash/debug data from it. This way the + * SMP watchdog can detect hardware interrupts off lockups. */ static cpumask_t wd_cpus_enabled __read_mostly; @@ -47,19 +80,7 @@ static u64 wd_timer_period_ms __read_mostly; /* interval between heartbeat */ static DEFINE_PER_CPU(struct timer_list, wd_timer); static DEFINE_PER_CPU(u64, wd_timer_tb); -/* - * These are for the SMP checker. CPUs clear their pending bit in their - * heartbeat. If the bitmask becomes empty, the time is noted and the - * bitmask is refilled. - * - * All CPUs clear their bit in the pending mask every timer period. - * Once all have cleared, the time is noted and the bits are reset. - * If the time since all clear was greater than the panic timeout, - * we can panic with the list of stuck CPUs. - * - * This will work best with NMI IPIs for crash code so the stuck CPUs - * can be pulled out to get their backtraces. - */ +/* SMP checker bits */ static unsigned long __wd_smp_lock; static cpumask_t wd_smp_cpus_pending; static cpumask_t wd_smp_cpus_stuck; @@ -90,7 +111,7 @@ static inline void wd_smp_unlock(unsigned long *flags) static void wd_lockup_ipi(struct pt_regs *regs) { - pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", raw_smp_processor_id()); + pr_emerg("CPU %d Hard LOCKUP\n", raw_smp_processor_id()); print_modules(); print_irqtrace_events(current); if (regs) @@ -131,8 +152,8 @@ static void watchdog_smp_panic(int cpu, u64 tb) if (cpumask_weight(&wd_smp_cpus_pending) == 0) goto out; - pr_emerg("Watchdog CPU:%d detected Hard LOCKUP other CPUS:%*pbl\n", - cpu, cpumask_pr_args(&wd_smp_cpus_pending)); + pr_emerg("CPU %d detected hard LOCKUP on other CPUs %*pbl\n", + cpu, cpumask_pr_args(&wd_smp_cpus_pending)); if (!sysctl_hardlockup_all_cpu_backtrace) { /* @@ -175,7 +196,7 @@ static void wd_smp_clear_cpu_pending(int cpu, u64 tb) if (unlikely(cpumask_test_cpu(cpu, &wd_smp_cpus_stuck))) { unsigned long flags; - pr_emerg("Watchdog CPU:%d became unstuck\n", cpu); + pr_emerg("CPU %d became unstuck\n", cpu); wd_smp_lock(&flags); cpumask_clear_cpu(cpu, &wd_smp_cpus_stuck); wd_smp_unlock(&flags); @@ -233,13 +254,10 @@ void soft_nmi_interrupt(struct pt_regs *regs) } set_cpu_stuck(cpu, tb); - pr_emerg("Watchdog CPU:%d Hard LOCKUP\n", cpu); + pr_emerg("CPU %d self-detected hard LOCKUP @ %pS\n", cpu, (void *)regs->nip); print_modules(); print_irqtrace_events(current); - if (regs) - show_regs(regs); - else - dump_stack(); + show_regs(regs); wd_smp_unlock(&flags); @@ -388,30 +406,8 @@ int __init watchdog_nmi_probe(void) "powerpc/watchdog:online", start_wd_on_cpu, stop_wd_on_cpu); if (err < 0) { - pr_warn("Watchdog could not be initialized"); + pr_warn("could not be initialized"); return err; } return 0; } - -static void handle_backtrace_ipi(struct pt_regs *regs) -{ - nmi_cpu_backtrace(regs); -} - -static void raise_backtrace_ipi(cpumask_t *mask) -{ - unsigned int cpu; - - for_each_cpu(cpu, mask) { - if (cpu == smp_processor_id()) - handle_backtrace_ipi(NULL); - else - smp_send_nmi_ipi(cpu, handle_backtrace_ipi, 1000000); - } -} - -void arch_trigger_cpumask_backtrace(const cpumask_t *mask, bool exclude_self) -{ - nmi_trigger_cpumask_backtrace(mask, exclude_self, raise_backtrace_ipi); -} |