From a4016a79fcbd139e7378944c0d86a39fdbc70ecc Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 14 May 2009 14:52:17 +0200 Subject: [PATCH] perf_counter: x86: Robustify interrupt handling Two consecutive NMIs could daze and confuse the machine when the first would handle the overflow of both counters. [ Impact: fix false-positive syslog messages under multi-session profiling ] Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Cc: Corey Ashford LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_counter.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 313638c..1dcf670 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -783,6 +783,10 @@ static int amd_pmu_handle_irq(struct pt_regs *regs, int nmi) counter = cpuc->counters[idx]; hwc = &counter->hw; + + if (counter->hw_event.nmi != nmi) + goto next; + val = x86_perf_counter_update(counter, hwc, idx); if (val & (1ULL << (x86_pmu.counter_bits - 1))) goto next; @@ -869,7 +873,6 @@ perf_counter_nmi_handler(struct notifier_block *self, { struct die_args *args = __args; struct pt_regs *regs; - int ret; if (!atomic_read(&active_counters)) return NOTIFY_DONE; @@ -886,9 +889,16 @@ perf_counter_nmi_handler(struct notifier_block *self, regs = args->regs; apic_write(APIC_LVTPC, APIC_DM_NMI); - ret = x86_pmu.handle_irq(regs, 1); + /* + * Can't rely on the handled return value to say it was our NMI, two + * counters could trigger 'simultaneously' raising two back-to-back NMIs. + * + * If the first NMI handles both, the latter will be empty and daze + * the CPU. + */ + x86_pmu.handle_irq(regs, 1); - return ret ? NOTIFY_STOP : NOTIFY_OK; + return NOTIFY_STOP; } static __read_mostly struct notifier_block perf_counter_nmi_notifier = { -- 1.8.2.3