Re: [PATCH v2] perf/core: fix a possible deadlock scenario

[Cong Wang]

Hi, Peter, Andi

While reviewing the deadlock, I find out it looks like we could have the
following infinite recursion too:

perf_event_account_interrupt()
__perf_event_account_interrupt()
perf_adjust_period()
event->pmu->stop
x86_pmu_stop()
x86_pmu.disable()
intel_pmu_disable_event()
intel_pmu_pebs_disable()
intel_pmu_drain_pebs_buffer()
intel_pmu_drain_pebs_nhm()
<repeat....>

This time is pure hardware events, attr.freq must be non-zero.

And, we could enter this infinite recursion in NMI handler too:

intel_pmu_handle_irq()
perf_event_overflow()
__perf_event_overflow()
__perf_event_account_interrupt()
....

Or this is impossible too?

Thanks!