The current comment for the barrier that guarantees that waiter
increment is always before taking the hb spinlock (barrier (A))
needs to be fixed. We are obviously referring to hb_waiters_inc,
which is a full barrier.
Reported-by: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Davidlohr Bueso <dbu...@suse.de>
---
kernel/futex.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/futex.c b/kernel/futex.c
index fdd312da0992..5ec2473a3497 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -2221,11 +2221,11 @@ static inline struct futex_hash_bucket
*queue_lock(struct futex_q *q)
* decrement the counter at queue_unlock() when some error has
* occurred and we don't end up adding the task to the list.
*/
- hb_waiters_inc(hb);
+ hb_waiters_inc(hb); /* implies smp_mb(); (A) */
q->lock_ptr = &hb->lock;
- spin_lock(&hb->lock); /* implies smp_mb(); (A) */
+ spin_lock(&hb->lock);
return hb;
}
--
2.16.4
