From: tip-bot for Omar Sandoval <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: tglx@linutronix.de, peterz@infradead.org,
torvalds@linux-foundation.org, hpa@zytor.com, axboe@kernel.dk,
linux-kernel@vger.kernel.org, mingo@kernel.org, osandov@fb.com
Subject: [tip:sched/core] sched/wait: Fix add_wait_queue() behavioral change
Date: Wed, 6 Dec 2017 12:28:53 -0800 [thread overview]
Message-ID: <tip-c6b9d9a33029014446bd9ed84c1688f6d3d4eab9@git.kernel.org> (raw)
In-Reply-To: <a16c8ccffd39bd08fdaa45a5192294c784b803a7.1512544324.git.osandov@fb.com>
Commit-ID: c6b9d9a33029014446bd9ed84c1688f6d3d4eab9
Gitweb: https://git.kernel.org/tip/c6b9d9a33029014446bd9ed84c1688f6d3d4eab9
Author: Omar Sandoval <osandov@fb.com>
AuthorDate: Tue, 5 Dec 2017 23:15:31 -0800
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 6 Dec 2017 19:30:34 +0100
sched/wait: Fix add_wait_queue() behavioral change
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 <osandov@fb.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: kernel-team@fb.com
Fixes: ("sched/wait: Standardize internal naming of wait-queue entries")
Link: http://lkml.kernel.org/r/a16c8ccffd39bd08fdaa45a5192294c784b803a7.1512544324.git.osandov@fb.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/wait.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index 98feab7..929ecb7 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -27,7 +27,7 @@ void add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq
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);
next prev parent reply other threads:[~2017-12-06 20:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-30 0:58 add_wait_queue() (unintentional?) behavior change in v4.13 Omar Sandoval
2017-11-30 2:37 ` Linus Torvalds
2017-12-06 7:15 ` [PATCH] sched/wait: fix add_wait_queue() behavior change Omar Sandoval
2017-12-06 16:11 ` Jens Axboe
2017-12-06 16:46 ` Ingo Molnar
2017-12-06 20:28 ` tip-bot for Omar Sandoval [this message]
2017-12-06 16:43 ` add_wait_queue() (unintentional?) behavior change in v4.13 Ingo Molnar
2017-12-06 2:35 ` Fubo Chen
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