diff options
| -rw-r--r-- | kernel/perf_event.c | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 49d8be5a45e3..34659d4085c7 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -1867,7 +1867,19 @@ int perf_event_release_kernel(struct perf_event *event) event->state = PERF_EVENT_STATE_FREE; WARN_ON_ONCE(ctx->parent_ctx); - mutex_lock(&ctx->mutex); + /* + * There are two ways this annotation is useful: + * + * 1) there is a lock recursion from perf_event_exit_task + * see the comment there. + * + * 2) there is a lock-inversion with mmap_sem through + * perf_event_read_group(), which takes faults while + * holding ctx->mutex, however this is called after + * the last filedesc died, so there is no possibility + * to trigger the AB-BA case. + */ + mutex_lock_nested(&ctx->mutex, SINGLE_DEPTH_NESTING); perf_event_remove_from_context(event); mutex_unlock(&ctx->mutex); @@ -5305,7 +5317,7 @@ void perf_event_exit_task(struct task_struct *child) * * But since its the parent context it won't be the same instance. */ - mutex_lock_nested(&child_ctx->mutex, SINGLE_DEPTH_NESTING); + mutex_lock(&child_ctx->mutex); again: list_for_each_entry_safe(child_event, tmp, &child_ctx->pinned_groups, |