With the new throttling/unthrottling code introduced with
commit:
e050e3f0a71b ("perf: Fix broken interrupt rate throttling")
we occasionally hit two WARN_ON_ONCE() checks in:
- intel_pmu_pebs_enable()
- intel_pmu_lbr_enable()
- x86_pmu_start()
The assertions are no longer problematic. There is a valid
path where they can trigger but it is harmless.
The assertion can be triggered with:
$ perf record -e instructions:pp ....
Leading to paths:
intel_pmu_pebs_enable
intel_pmu_enable_event
x86_perf_event_set_period
x86_pmu_start
perf_adjust_freq_unthr_context
perf_event_task_tick
scheduler_tick
And:
intel_pmu_lbr_enable
intel_pmu_enable_event
x86_perf_event_set_period
x86_pmu_start
perf_adjust_freq_unthr_context.
perf_event_task_tick
scheduler_tick
cpuc->enabled is always on because when we get to
perf_adjust_freq_unthr_context() the PMU is not totally
disabled. Furthermore when we need to adjust a period,
we only stop the event we need to change and not the
entire PMU. Thus, when we re-enable, cpuc->enabled is
already set. Note that when we stop the event, both
pebs and lbr are stopped if necessary (and possible).
Signed-off-by: Stephane Eranian <eranian@google.com>
Cc: peterz@infradead.org
Link: http://lkml.kernel.org/r/20120202110401.GA30911@quad
Signed-off-by: Ingo Molnar <mingo@elte.hu>
struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
int idx = event->hw.idx;
- if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
- return;
-
if (WARN_ON_ONCE(idx == -1))
return;
hwc->config &= ~ARCH_PERFMON_EVENTSEL_INT;
cpuc->pebs_enabled |= 1ULL << hwc->idx;
- WARN_ON_ONCE(cpuc->enabled);
if (x86_pmu.intel_cap.pebs_trap && event->attr.precise_ip > 1)
intel_pmu_lbr_enable(event);
if (!x86_pmu.lbr_nr)
return;
- WARN_ON_ONCE(cpuc->enabled);
-
/*
* Reset the LBR stack if we changed task context to
* avoid data leaks.