perf: Fix context leak in put_event()

Commit:

  a83fe28 ("perf: Fix put_event() ctx lock")

changed the locking logic in put_event() by replacing mutex_lock_nested()
with perf_event_ctx_lock_nested(), but didn't fix the subsequent
mutex_unlock() with a correct counterpart, perf_event_ctx_unlock().

Contexts are thus leaked as a result of incremented refcount
in perf_event_ctx_lock_nested().

Signed-off-by: Leon Yu <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Paul Mackerras <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Fixes: a83fe28 ("perf: Fix put_event() ctx lock")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

Author: clyu

kernel/events/core.c

@@ -3591,7 +3591,7 @@ static void put_event(struct perf_event *event)
 	ctx = perf_event_ctx_lock_nested(event, SINGLE_DEPTH_NESTING);
 	WARN_ON_ONCE(ctx->parent_ctx);
 	perf_remove_from_context(event, true);
-	mutex_unlock(&ctx->mutex);
+	perf_event_ctx_unlock(event, ctx);
 
 	_free_event(event);
 }