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Commit 6f10581a authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf: Fix locking for PERF_FORMAT_GROUP 



We should hold event->child_mutex when iterating the inherited
counters, we should hold ctx->mutex when iterating siblings.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20091120212509.251030114@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 59ed446f

kernel/perf_event.c

+13 −7
Original line number Diff line number Diff line
@@ -1782,6 +1782,7 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running) 
	*enabled = 0;

	*running = 0;



	mutex_lock(&event->child_mutex);

	total += perf_event_read(event);

	*enabled += event->total_time_enabled +

			atomic64_read(&event->child_total_time_enabled);
@@ -1793,6 +1794,7 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running) 
		*enabled += child->total_time_enabled;

		*running += child->total_time_running;

	}

	mutex_unlock(&event->child_mutex);



	return total;

}
@@ -1802,10 +1804,12 @@ static int perf_event_read_group(struct perf_event *event, 
				   u64 read_format, char __user *buf)

{

	struct perf_event *leader = event->group_leader, *sub;

	int n = 0, size = 0, ret = 0;

	int n = 0, size = 0, ret = -EFAULT;

	struct perf_event_context *ctx = leader->ctx;

	u64 values[5];

	u64 count, enabled, running;



	mutex_lock(&ctx->mutex);

	count = perf_event_read_value(leader, &enabled, &running);



	values[n++] = 1 + leader->nr_siblings;
@@ -1820,9 +1824,9 @@ static int perf_event_read_group(struct perf_event *event, 
	size = n * sizeof(u64);



	if (copy_to_user(buf, values, size))

		return -EFAULT;

		goto unlock;



	ret += size;

	ret = size;



	list_for_each_entry(sub, &leader->sibling_list, group_entry) {

		n = 0;
@@ -1833,11 +1837,15 @@ static int perf_event_read_group(struct perf_event *event, 


		size = n * sizeof(u64);



		if (copy_to_user(buf + size, values, size))

			return -EFAULT;

		if (copy_to_user(buf + size, values, size)) {

			ret = -EFAULT;

			goto unlock;

		}



		ret += size;

	}

unlock:

	mutex_unlock(&ctx->mutex);



	return ret;

}
@@ -1884,12 +1892,10 @@ perf_read_hw(struct perf_event *event, char __user *buf, size_t count) 
		return -ENOSPC;



	WARN_ON_ONCE(event->ctx->parent_ctx);

	mutex_lock(&event->child_mutex);

	if (read_format & PERF_FORMAT_GROUP)

		ret = perf_event_read_group(event, read_format, buf);

	else

		ret = perf_event_read_one(event, read_format, buf);

	mutex_unlock(&event->child_mutex);



	return ret;

}