4.14-stable review patch. If anyone has any objections, please let me know.
------------------
From: Omar Sandoval <osan...@fb.com>
commit c6b9d9a33029014446bd9ed84c1688f6d3d4eab9 upstream.
The following cleanup commit:
50816c48997a ("sched/wait: Standardize internal naming of wait-queue entries")
... unintentionally changed the behavior of add_wait_queue() from
inserting the wait entry at the head of the wait queue to the tail
of the wait queue.
Beyond a negative performance impact this change in behavior
theoretically also breaks wait queues which mix exclusive and
non-exclusive waiters, as non-exclusive waiters will not be
woken up if they are queued behind enough exclusive waiters.
Signed-off-by: Omar Sandoval <osan...@fb.com>
Reviewed-by: Jens Axboe <ax...@kernel.dk>
Acked-by: Peter Zijlstra <pet...@infradead.org>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: kernel-t...@fb.com
Fixes: ("sched/wait: Standardize internal naming of wait-queue entries")
Link:
http://lkml.kernel.org/r/a16c8ccffd39bd08fdaa45a5192294c784b803a7.1512544324.git.osan...@fb.com
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
kernel/sched/wait.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -27,7 +27,7 @@ void add_wait_queue(struct wait_queue_he
wq_entry->flags &= ~WQ_FLAG_EXCLUSIVE;
spin_lock_irqsave(&wq_head->lock, flags);
- __add_wait_queue_entry_tail(wq_head, wq_entry);
+ __add_wait_queue(wq_head, wq_entry);
spin_unlock_irqrestore(&wq_head->lock, flags);
}
EXPORT_SYMBOL(add_wait_queue);
