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-rw-r--r--kernel/futex.c6
1 files changed, 6 insertions, 0 deletions
diff --git a/kernel/futex.c b/kernel/futex.c
index 5872e3507f3..5e71a6bf6f6 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -270,7 +270,13 @@ static void wake_futex(struct futex_q *q)
/*
* The waiting task can free the futex_q as soon as this is written,
* without taking any locks. This must come last.
+ *
+ * A memory barrier is required here to prevent the following store
+ * to lock_ptr from getting ahead of the wakeup. Clearing the lock
+ * at the end of wake_up_all() does not prevent this store from
+ * moving.
*/
+ wmb();
q->lock_ptr = NULL;
}