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Commit 7d88962e authored by Sukadev Bhattiprolu's avatar Sukadev Bhattiprolu Committed by Ingo Molnar
Browse files

perf/core: Add return value for perf_event_read() 



When we implement the ability to read several counters at once (using
the PERF_PMU_TXN_READ transaction interface), perf_event_read() can
fail when the 'group' parameter is true (eg: trying to read too many
events at once).

For now, have perf_event_read() return an integer. Ignore the return
value when the 'group' parameter is false.

Signed-off-by: default avatarSukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Link: http://lkml.kernel.org/r/1441336073-22750-8-git-send-email-sukadev@linux.vnet.ibm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent fa8c2693

kernel/events/core.c

+34 −11
Original line number Diff line number Diff line
@@ -3187,6 +3187,7 @@ void perf_event_exec(void) 
struct perf_read_data {

	struct perf_event *event;

	bool group;

	int ret;

};



/*
@@ -3227,6 +3228,7 @@ static void __perf_event_read(void *info) 
		if (sub->state == PERF_EVENT_STATE_ACTIVE)

			sub->pmu->read(sub);

	}

	data->ret = 0;



unlock:

	raw_spin_unlock(&ctx->lock);
@@ -3293,8 +3295,10 @@ u64 perf_event_read_local(struct perf_event *event) 
	return val;

}



static void perf_event_read(struct perf_event *event, bool group)

static int perf_event_read(struct perf_event *event, bool group)

{

	int ret = 0;



	/*

	 * If event is enabled and currently active on a CPU, update the

	 * value in the event structure:
@@ -3303,9 +3307,11 @@ static void perf_event_read(struct perf_event *event, bool group) 
		struct perf_read_data data = {

			.event = event,

			.group = group,

			.ret = 0,

		};

		smp_call_function_single(event->oncpu,

					 __perf_event_read, &data, 1);

		ret = data.ret;

	} else if (event->state == PERF_EVENT_STATE_INACTIVE) {

		struct perf_event_context *ctx = event->ctx;

		unsigned long flags;
@@ -3326,6 +3332,8 @@ static void perf_event_read(struct perf_event *event, bool group) 
			update_event_times(event);

		raw_spin_unlock_irqrestore(&ctx->lock, flags);

	}



	return ret;

}



/*
@@ -3842,7 +3850,7 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running) 


	mutex_lock(&event->child_mutex);



	perf_event_read(event, false);

	(void)perf_event_read(event, false);

	total += perf_event_count(event);



	*enabled += event->total_time_enabled +
@@ -3851,7 +3859,7 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running) 
			atomic64_read(&event->child_total_time_running);



	list_for_each_entry(child, &event->child_list, child_list) {

		perf_event_read(child, false);

		(void)perf_event_read(child, false);

		total += perf_event_count(child);

		*enabled += child->total_time_enabled;

		*running += child->total_time_running;
@@ -3862,13 +3870,16 @@ u64 perf_event_read_value(struct perf_event *event, u64 *enabled, u64 *running) 
}

EXPORT_SYMBOL_GPL(perf_event_read_value);



static void __perf_read_group_add(struct perf_event *leader,

static int __perf_read_group_add(struct perf_event *leader,

					u64 read_format, u64 *values)

{

	struct perf_event *sub;

	int n = 1; /* skip @nr */

	int ret;



	perf_event_read(leader, true);

	ret = perf_event_read(leader, true);

	if (ret)

		return ret;



	/*

	 * Since we co-schedule groups, {enabled,running} times of siblings
@@ -3897,6 +3908,8 @@ static void __perf_read_group_add(struct perf_event *leader, 
		if (read_format & PERF_FORMAT_ID)

			values[n++] = primary_event_id(sub);

	}



	return 0;

}



static int perf_read_group(struct perf_event *event,
@@ -3904,7 +3917,7 @@ static int perf_read_group(struct perf_event *event, 
{

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

	struct perf_event_context *ctx = leader->ctx;

	int ret = event->read_size;

	int ret;

	u64 *values;



	lockdep_assert_held(&ctx->mutex);
@@ -3921,17 +3934,27 @@ static int perf_read_group(struct perf_event *event, 
	 */

	mutex_lock(&leader->child_mutex);



	__perf_read_group_add(leader, read_format, values);

	list_for_each_entry(child, &leader->child_list, child_list)

		__perf_read_group_add(child, read_format, values);

	ret = __perf_read_group_add(leader, read_format, values);

	if (ret)

		goto unlock;



	list_for_each_entry(child, &leader->child_list, child_list) {

		ret = __perf_read_group_add(child, read_format, values);

		if (ret)

			goto unlock;

	}



	mutex_unlock(&leader->child_mutex);



	ret = event->read_size;

	if (copy_to_user(buf, values, event->read_size))

		ret = -EFAULT;

	goto out;



unlock:

	mutex_unlock(&leader->child_mutex);

out:

	kfree(values);



	return ret;

}
@@ -4037,7 +4060,7 @@ static unsigned int perf_poll(struct file *file, poll_table *wait) 


static void _perf_event_reset(struct perf_event *event)

{

	perf_event_read(event, false);

	(void)perf_event_read(event, false);

	local64_set(&event->count, 0);

	perf_event_update_userpage(event);

}