Commit-ID: e30e08f65c7ef6c230424264f09c3d53f117f58b
Gitweb: http://git.kernel.org/tip/e30e08f65c7ef6c230424264f09c3d53f117f58b
Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
AuthorDate: Wed, 8 Apr 2009 15:01:25 +0200
Committer: Ingo Molnar <mingo@xxxxxxx>
CommitDate: Wed, 8 Apr 2009 18:53:27 +0200
perf_counter: fix NMI race in task clock
We should not be updating ctx->time from NMI context, work around that.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Corey Ashford <cjashfor@xxxxxxxxxxxxxxxxxx>
LKML-Reference: <20090408130408.681326666@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
kernel/perf_counter.c | 25 ++++++++++++++++---------
1 files changed, 16 insertions(+), 9 deletions(-)
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 863703b..84a3908 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -319,8 +319,6 @@ static void __perf_counter_disable(void *info)
spin_lock_irqsave(&ctx->lock, flags);
- update_context_time(ctx);
-
/*
* If the counter is on, turn it off.
* If it is in error state, leave it in error state.
@@ -2335,13 +2333,11 @@ static const struct hw_perf_counter_ops perf_ops_cpu_clock = {
* Software counter: task time clock
*/
-static void task_clock_perf_counter_update(struct perf_counter *counter)
+static void task_clock_perf_counter_update(struct perf_counter *counter, u64 now)
{
- u64 prev, now;
+ u64 prev;
s64 delta;
- now = counter->ctx->time;
-
prev = atomic64_xchg(&counter->hw.prev_count, now);
delta = now - prev;
atomic64_add(delta, &counter->count);
@@ -2369,13 +2365,24 @@ static int task_clock_perf_counter_enable(struct perf_counter *counter)
static void task_clock_perf_counter_disable(struct perf_counter *counter)
{
hrtimer_cancel(&counter->hw.hrtimer);
- task_clock_perf_counter_update(counter);
+ task_clock_perf_counter_update(counter, counter->ctx->time);
+
}
static void task_clock_perf_counter_read(struct perf_counter *counter)
{
- update_context_time(counter->ctx);
- task_clock_perf_counter_update(counter);
+ u64 time;
+
+ if (!in_nmi()) {
+ update_context_time(counter->ctx);
+ time = counter->ctx->time;
+ } else {
+ u64 now = perf_clock();
+ u64 delta = now - counter->ctx->timestamp;
+ time = counter->ctx->time + delta;
+ }
+
+ task_clock_perf_counter_update(counter, time);
}
static const struct hw_perf_counter_ops perf_ops_task_clock = {
--
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