Stephane Eranian f39d47ff81 perf: Fix double start/stop in x86_pmu_start() ... The following patch fixes a bug introduced by the following commit: e050e3f0a7 ("perf: Fix broken interrupt rate throttling") The patch caused the following warning to pop up depending on the sampling frequency adjustments: ------------[ cut here ]------------ WARNING: at arch/x86/kernel/cpu/perf_event.c:995 x86_pmu_start+0x79/0xd4() It was caused by the following call sequence: perf_adjust_freq_unthr_context.part() { stop() if (delta > 0) { perf_adjust_period() { if (period > 8*...) { stop() ... start() } } } start() } Which caused a double start and a double stop, thus triggering the assert in x86_pmu_start(). The patch fixes the problem by avoiding the double calls. We pass a new argument to perf_adjust_period() to indicate whether or not the event is already stopped. We can't just remove the start/stop from that function because it's called from __perf_event_overflow where the event needs to be reloaded via a stop/start back-toback call. The patch reintroduces the assertion in x86_pmu_start() which was removed by commit: 84f2b9b ("perf: Remove deprecated WARN_ON_ONCE()") In this second version, we've added calls to disable/enable PMU during unthrottling or frequency adjustment based on bug report of spurious NMI interrupts from Eric Dumazet. Reported-and-tested-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: Stephane Eranian <eranian@google.com> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: markus@trippelsdorf.de Cc: paulus@samba.org Link: http://lkml.kernel.org/r/20120207133956.GA4932@quad [ Minor edits to the changelog and to the code ] Signed-off-by: Ingo Molnar <mingo@elte.hu>		2012-02-07 16:58:56 +01:00
..
callchain.c	perf: Don't call release_callchain_buffers() if allocation fails	2012-01-21 09:33:41 +01:00
core.c	perf: Fix double start/stop in x86_pmu_start()	2012-02-07 16:58:56 +01:00
hw_breakpoint.c
internal.h	Merge branch 'perf/urgent' into perf/core	2011-12-06 06:43:49 +01:00
Makefile	perf: Carve out callchain functionality	2011-11-14 13:31:26 +01:00
ring_buffer.c	Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial	2012-01-08 13:21:22 -08:00