diff options
Diffstat (limited to 'arch/arm/kernel/perf_event.c')
| -rw-r--r-- | arch/arm/kernel/perf_event.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/arm/kernel/perf_event.c b/arch/arm/kernel/perf_event.c index 56173ae16448..b2abfa18f137 100644 --- a/arch/arm/kernel/perf_event.c +++ b/arch/arm/kernel/perf_event.c @@ -680,6 +680,28 @@ static void __init cpu_pmu_init(struct arm_pmu *armpmu) } /* + * PMU hardware loses all context when a CPU goes offline. + * When a CPU is hotplugged back in, since some hardware registers are + * UNKNOWN at reset, the PMU must be explicitly reset to avoid reading + * junk values out of them. + */ +static int __cpuinit pmu_cpu_notify(struct notifier_block *b, + unsigned long action, void *hcpu) +{ + if ((action & ~CPU_TASKS_FROZEN) != CPU_STARTING) + return NOTIFY_DONE; + + if (cpu_pmu && cpu_pmu->reset) + cpu_pmu->reset(NULL); + + return NOTIFY_OK; +} + +static struct notifier_block __cpuinitdata pmu_cpu_notifier = { + .notifier_call = pmu_cpu_notify, +}; + +/* * CPU PMU identification and registration. */ static int __init @@ -730,6 +752,7 @@ init_hw_perf_events(void) pr_info("enabled with %s PMU driver, %d counters available\n", cpu_pmu->name, cpu_pmu->num_events); cpu_pmu_init(cpu_pmu); + register_cpu_notifier(&pmu_cpu_notifier); armpmu_register(cpu_pmu, "cpu", PERF_TYPE_RAW); } else { pr_info("no hardware support available\n"); |