From 9029a5e3801f1cc7cdaab80169d82427acf928d8 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 15 May 2009 08:26:20 +0200 Subject: [PATCH] perf_counter: x86: Protect against infinite loops in intel_pmu_handle_irq() intel_pmu_handle_irq() can lock up in an infinite loop if the hardware does not allow the acking of irqs. Alas, this happened in testing so make this robust and emit a warning if it happens in the future. Also, clean up the IRQ handlers a bit. [ Impact: improve perfcounter irq/nmi handling robustness ] Acked-by: Peter Zijlstra Cc: Paul Mackerras Cc: Corey Ashford LKML-Reference: Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/perf_counter.c | 25 ++++++++++++++++++------- 1 file changed, 18 insertions(+), 7 deletions(-) diff --git a/arch/x86/kernel/cpu/perf_counter.c b/arch/x86/kernel/cpu/perf_counter.c index 46a82d1e4cbe..5a7f718eb1e1 100644 --- a/arch/x86/kernel/cpu/perf_counter.c +++ b/arch/x86/kernel/cpu/perf_counter.c @@ -722,9 +722,13 @@ static void intel_pmu_save_and_restart(struct perf_counter *counter) */ static int intel_pmu_handle_irq(struct pt_regs *regs, int nmi) { - int bit, cpu = smp_processor_id(); + struct cpu_hw_counters *cpuc; + struct cpu_hw_counters; + int bit, cpu, loops; u64 ack, status; - struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu); + + cpu = smp_processor_id(); + cpuc = &per_cpu(cpu_hw_counters, cpu); perf_disable(); status = intel_pmu_get_status(); @@ -733,7 +737,13 @@ static int intel_pmu_handle_irq(struct pt_regs *regs, int nmi) return 0; } + loops = 0; again: + if (++loops > 100) { + WARN_ONCE(1, "perfcounters: irq loop stuck!\n"); + return 1; + } + inc_irq_stat(apic_perf_irqs); ack = status; for_each_bit(bit, (unsigned long *)&status, X86_PMC_IDX_MAX) { @@ -765,13 +775,14 @@ again: static int amd_pmu_handle_irq(struct pt_regs *regs, int nmi) { - int cpu = smp_processor_id(); - struct cpu_hw_counters *cpuc = &per_cpu(cpu_hw_counters, cpu); - u64 val; - int handled = 0; + int cpu, idx, throttle = 0, handled = 0; + struct cpu_hw_counters *cpuc; struct perf_counter *counter; struct hw_perf_counter *hwc; - int idx, throttle = 0; + u64 val; + + cpu = smp_processor_id(); + cpuc = &per_cpu(cpu_hw_counters, cpu); if (++cpuc->interrupts == PERFMON_MAX_INTERRUPTS) { throttle = 1; -- 2.20.1