perf/core: Invert perf_read_group() loops

}

EXPORT_SYMBOL_GPL(perf_event_read_value);

static int perf_read_group(struct perf_event *event,

				   u64 read_format, char __user *buf)

static void __perf_read_group_add(struct perf_event *leader,

					u64 read_format, u64 *values)

{

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

	struct perf_event_context *ctx = leader->ctx;

	int n = 0, size = 0, ret;

	u64 count, enabled, running;

	u64 values[5];

	struct perf_event *sub;

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

	lockdep_assert_held(&ctx->mutex);

	perf_event_read(leader, true);

	/*

	 * Since we co-schedule groups, {enabled,running} times of siblings

	 * will be identical to those of the leader, so we only publish one

	 * set.

	 */

	if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED) {

		values[n++] += leader->total_time_enabled +

			atomic64_read(&leader->child_total_time_enabled);

	}

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

	if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING) {

		values[n++] += leader->total_time_running +

			atomic64_read(&leader->child_total_time_running);

	}

	values[n++] = 1 + leader->nr_siblings;

	if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)

		values[n++] = enabled;

	if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)

		values[n++] = running;

	values[n++] = count;

	/*

	 * Write {count,id} tuples for every sibling.

	 */

	values[n++] += perf_event_count(leader);

	if (read_format & PERF_FORMAT_ID)

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

	size = n * sizeof(u64);

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

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

		if (read_format & PERF_FORMAT_ID)

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

	}

}

static int perf_read_group(struct perf_event *event,

				   u64 read_format, char __user *buf)

{

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

	struct perf_event_context *ctx = leader->ctx;

	int ret = event->read_size;

	u64 *values;

	if (copy_to_user(buf, values, size))

		return -EFAULT;

	lockdep_assert_held(&ctx->mutex);

	ret = size;

	values = kzalloc(event->read_size, GFP_KERNEL);

	if (!values)

		return -ENOMEM;

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

		n = 0;

	values[0] = 1 + leader->nr_siblings;

		values[n++] = perf_event_read_value(sub, &enabled, &running);

		if (read_format & PERF_FORMAT_ID)

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

	/*

	 * By locking the child_mutex of the leader we effectively

	 * lock the child list of all siblings.. XXX explain how.

	 */

	mutex_lock(&leader->child_mutex);

		size = n * sizeof(u64);

	__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);

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

			return -EFAULT;

		}

	mutex_unlock(&leader->child_mutex);

		ret += size;

	}

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

		ret = -EFAULT;

	kfree(values);

	return ret;

}