diff options
authorMatt Evans <matt@ozlabs.org>2010-07-05 17:36:32 +0000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-07-08 18:11:37 +1000
commit219a92a4c40db2fac604f63bce9a5a3fe1967879 (patch)
parent2aa72f612144a0a7d4b0b22ae7c122692ac6a013 (diff)
powerpc/perf_event: Fix for power_pmu_disable()
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> Acked-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/powerpc/kernel/perf_event.c b/arch/powerpc/kernel/perf_event.c
index 43b83c35cf5..5c14ffe5125 100644
--- a/arch/powerpc/kernel/perf_event.c
+++ b/arch/powerpc/kernel/perf_event.c
@@ -791,8 +791,11 @@ 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];
+ }
ppmu->disable_pmc(event->hw.idx - 1, cpuhw->mmcr);
if (event->hw.idx) {