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Commit e30e08f6 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: fix NMI race in task clock 



We should not be updating ctx->time from NMI context, work around that.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
LKML-Reference: <20090408130408.681326666@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 7333a800

kernel/perf_counter.c

+16 −9
Original line number Diff line number Diff line
@@ -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)

{

	u64 time;



	if (!in_nmi()) {

		update_context_time(counter->ctx);

	task_clock_perf_counter_update(counter);

		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 = {