[PATCH 11/14] futex: Verify exit_mutex ownership in futex_exit_recursive()

[Bart Van Assche]

futex_exit_recursive() unlocks tsk->futex.exit_mutex if the futex state
is FUTEX_STATE_EXITING. It uses __assume_ctx_lock() to inform Clang's
context analysis that this mutex is held. However, __assume_ctx_lock()
does not verify that assumption. Convert the __assume_ctx_lock() call
into a lockdep_assume_ctx_held() call such that the lock ownership
assumption is also verified at runtime by lockdep.

Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Signed-off-by: Bart Van Assche <bvanassche@xxxxxxx>
---
 kernel/futex/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/futex/core.c b/kernel/futex/core.c
index a240638f69e5..4e5aa0160dd2 100644
--- a/kernel/futex/core.c
+++ b/kernel/futex/core.c
@@ -1503,7 +1503,7 @@ void futex_exit_recursive(struct task_struct *tsk)
 {
 	/* If the state is FUTEX_STATE_EXITING then futex_exit_mutex is held */
 	if (tsk->futex.state == FUTEX_STATE_EXITING) {
-		__assume_ctx_lock(&tsk->futex.exit_mutex);
+		lockdep_assume_ctx_held(&tsk->futex.exit_mutex);
 		mutex_unlock(&tsk->futex.exit_mutex);
 	}
 	tsk->futex.state = FUTEX_STATE_DEAD;