52 lines
2 KiB
Diff
52 lines
2 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Omar Sandoval <osandov@fb.com>
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Date: Tue, 5 Dec 2017 23:15:31 -0800
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Subject: [PATCH] sched/wait: Fix add_wait_queue() behavioral change
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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The following cleanup commit:
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50816c48997a ("sched/wait: Standardize internal naming of wait-queue entries")
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... unintentionally changed the behavior of add_wait_queue() from
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inserting the wait entry at the head of the wait queue to the tail
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of the wait queue.
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Beyond a negative performance impact this change in behavior
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theoretically also breaks wait queues which mix exclusive and
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non-exclusive waiters, as non-exclusive waiters will not be
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woken up if they are queued behind enough exclusive waiters.
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Signed-off-by: Omar Sandoval <osandov@fb.com>
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Reviewed-by: Jens Axboe <axboe@kernel.dk>
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Acked-by: Peter Zijlstra <peterz@infradead.org>
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Cc: Linus Torvalds <torvalds@linux-foundation.org>
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Cc: Thomas Gleixner <tglx@linutronix.de>
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Cc: kernel-team@fb.com
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Fixes: ("sched/wait: Standardize internal naming of wait-queue entries")
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Link: http://lkml.kernel.org/r/a16c8ccffd39bd08fdaa45a5192294c784b803a7.1512544324.git.osandov@fb.com
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Signed-off-by: Ingo Molnar <mingo@kernel.org>
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(cherry picked from commit c6b9d9a33029014446bd9ed84c1688f6d3d4eab9)
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Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>
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---
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kernel/sched/wait.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
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index d6afed6d0752..c09ebe92a40a 100644
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--- a/kernel/sched/wait.c
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+++ b/kernel/sched/wait.c
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@@ -27,7 +27,7 @@ void add_wait_queue(struct wait_queue_head *wq_head, struct wait_queue_entry *wq
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wq_entry->flags &= ~WQ_FLAG_EXCLUSIVE;
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spin_lock_irqsave(&wq_head->lock, flags);
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- __add_wait_queue_entry_tail(wq_head, wq_entry);
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+ __add_wait_queue(wq_head, wq_entry);
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spin_unlock_irqrestore(&wq_head->lock, flags);
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}
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EXPORT_SYMBOL(add_wait_queue);
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--
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2.14.2
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