}
EXPORT_SYMBOL_GPL(perf_event_read_value);
-static int perf_event_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;
+ struct perf_event *sub;
+ int n = 1; /* skip @nr */
u64 count, enabled, running;
- u64 values[5];
-
- lockdep_assert_held(&ctx->mutex);
count = perf_event_read_value(leader, &enabled, &running);
- values[n++] = 1 + leader->nr_siblings;
+ /*
+ * 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++] = enabled;
if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
values[n++] = running;
- values[n++] = count;
+
+ /*
+ * Write {count,id} tuples for every sibling.
+ */
+ values[n++] += count;
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(leader);
- size = n * sizeof(u64);
-
- if (copy_to_user(buf, values, size))
- return -EFAULT;
-
- ret = size;
-
list_for_each_entry(sub, &leader->sibling_list, group_entry) {
- n = 0;
-
values[n++] = perf_event_read_value(sub, &enabled, &running);
if (read_format & PERF_FORMAT_ID)
values[n++] = primary_event_id(sub);
+ }
+}
- size = n * sizeof(u64);
+static int perf_event_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 + ret, values, size)) {
- return -EFAULT;
- }
+ lockdep_assert_held(&ctx->mutex);
- ret += size;
- }
+ values = kzalloc(event->read_size, GFP_KERNEL);
+ if (!values)
+ return -ENOMEM;
+
+ values[0] = 1 + leader->nr_siblings;
+
+ /*
+ * 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);
+
+ __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);
+
+ mutex_unlock(&leader->child_mutex);
+
+ if (copy_to_user(buf, values, event->read_size))
+ ret = -EFAULT;
+
+ kfree(values);
return ret;
}