| Message ID | 4C32A4C0.3000600@ozlabs.org (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Commit | 02475c6e8b300f0df5549a879318be610a94e756 |
| Delegated to: | Benjamin Herrenschmidt |
| Headers | show |
diff --git a/arch/powerpc/kernel/perf_event.c b/arch/powerpc/kernel/perf_event.c index 08460a2..3766398 100644 --- a/arch/powerpc/kernel/perf_event.c +++ b/arch/powerpc/kernel/perf_event.c @@ -838,8 +838,11 @@ static void power_pmu_disable(struct perf_event *event) cpuhw = &__get_cpu_var(cpu_hw_events); for (i = 0; i < cpuhw->n_events; ++i) { if (event == cpuhw->event[i]) { - while (++i < cpuhw->n_events) + while (++i < cpuhw->n_events) { cpuhw->event[i-1] = cpuhw->event[i]; + cpuhw->events[i-1] = cpuhw->events[i]; + cpuhw->flags[i-1] = cpuhw->flags[i]; + } --cpuhw->n_events; ppmu->disable_pmc(event->hw.idx - 1, cpuhw->mmcr); if (event->hw.idx) {
When power_pmu_disable() removes the given event from a particular index into cpuhw->event[], it shuffles down higher event[] entries. But, this array is paired with cpuhw->events[] and cpuhw->flags[] so should shuffle them similarly. If these arrays get out of sync, code such as power_check_constraints() will fail. This caused a bug where events were temporarily disabled and then failed to be re-enabled; subsequent code tried to write_pmc() with its (disabled) idx of 0, causing a message "oops trying to write PMC0". This triggers this bug on POWER7, running a miss-heavy test: perf record -e L1-dcache-load-misses -e L1-dcache-store-misses ./misstest Signed-off-by: Matt Evans <matt@ozlabs.org> --- arch/powerpc/kernel/perf_event.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-)