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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2010-03-11 13:40:30 +0100
committerIngo Molnar <mingo@elte.hu>2010-03-11 15:21:28 +0100
commit45e16a6834b6af098702e5ea6c9a40de42ff77d8 (patch)
tree401649ce862d60960b47c9261a16346a51a72c14 /arch/x86
parent85cfabbcd10f8d112feee6e2ec64ee78033b6d3c (diff)
perf, x86: Fix hw_perf_enable() event assignment
What happens is that we schedule badly like: <...>-1987 [019] 280.252808: x86_pmu_start: event-46/1300c0: idx: 0 <...>-1987 [019] 280.252811: x86_pmu_start: event-47/1300c0: idx: 1 <...>-1987 [019] 280.252812: x86_pmu_start: event-48/1300c0: idx: 2 <...>-1987 [019] 280.252813: x86_pmu_start: event-49/1300c0: idx: 3 <...>-1987 [019] 280.252814: x86_pmu_start: event-50/1300c0: idx: 32 <...>-1987 [019] 280.252825: x86_pmu_stop: event-46/1300c0: idx: 0 <...>-1987 [019] 280.252826: x86_pmu_stop: event-47/1300c0: idx: 1 <...>-1987 [019] 280.252827: x86_pmu_stop: event-48/1300c0: idx: 2 <...>-1987 [019] 280.252828: x86_pmu_stop: event-49/1300c0: idx: 3 <...>-1987 [019] 280.252829: x86_pmu_stop: event-50/1300c0: idx: 32 <...>-1987 [019] 280.252834: x86_pmu_start: event-47/1300c0: idx: 1 <...>-1987 [019] 280.252834: x86_pmu_start: event-48/1300c0: idx: 2 <...>-1987 [019] 280.252835: x86_pmu_start: event-49/1300c0: idx: 3 <...>-1987 [019] 280.252836: x86_pmu_start: event-50/1300c0: idx: 32 <...>-1987 [019] 280.252837: x86_pmu_start: event-51/1300c0: idx: 32 *FAIL* This happens because we only iterate the n_running events in the first pass, and reset their index to -1 if they don't match to force a re-assignment. Now, in our RR example, n_running == 0 because we fully unscheduled, so event-50 will retain its idx==32, even though in scheduling it will have gotten idx=0, and we don't trigger the re-assign path. The easiest way to fix this is the below patch, which simply validates the full assignment in the second pass. Reported-by: Stephane Eranian <eranian@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1268311069.5037.31.camel@laptop> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/kernel/cpu/perf_event.c12
1 files changed, 3 insertions, 9 deletions
diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index c6bde7d7afdc..5fb490c6ee5c 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -811,7 +811,6 @@ void hw_perf_enable(void)
* step2: reprogram moved events into new counters
*/
for (i = 0; i < n_running; i++) {
-
event = cpuc->event_list[i];
hwc = &event->hw;
@@ -826,21 +825,16 @@ void hw_perf_enable(void)
continue;
x86_pmu_stop(event);
-
- hwc->idx = -1;
}
for (i = 0; i < cpuc->n_events; i++) {
-
event = cpuc->event_list[i];
hwc = &event->hw;
- if (i < n_running &&
- match_prev_assignment(hwc, cpuc, i))
- continue;
-
- if (hwc->idx == -1)
+ if (!match_prev_assignment(hwc, cpuc, i))
x86_assign_hw_event(event, cpuc, i);
+ else if (i < n_running)
+ continue;
x86_pmu_start(event);
}