Commit 9029a5e3 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

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: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 1c80f4b5

arch/x86/kernel/cpu/perf_counter.c

+18 −7
Original line number Diff line number Diff line
@@ -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;

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