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authorStephane Eranian <eranian@google.com>2012-02-07 08:39:57 -0500
committerIngo Molnar <mingo@elte.hu>2012-02-07 10:58:56 -0500
commitf39d47ff819ed52a2afbdbecbe35f23f7755f58d (patch)
tree6fcd6c2b9f6e7416da43065d866bd40d68bb9bc4 /arch
parent136e0b8eabb2913b589fc7fbd418f4d6805dbb56 (diff)
perf: Fix double start/stop in x86_pmu_start()
The following patch fixes a bug introduced by the following commit: e050e3f0a71b ("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>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kernel/cpu/perf_event.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index 2a30e5ae6acf..5adce1040b11 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -986,6 +986,9 @@ static void x86_pmu_start(struct perf_event *event, int flags)
986 struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events); 986 struct cpu_hw_events *cpuc = &__get_cpu_var(cpu_hw_events);
987 int idx = event->hw.idx; 987 int idx = event->hw.idx;
988 988
989 if (WARN_ON_ONCE(!(event->hw.state & PERF_HES_STOPPED)))
990 return;
991
989 if (WARN_ON_ONCE(idx == -1)) 992 if (WARN_ON_ONCE(idx == -1))
990 return; 993 return;
991 994