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@@ -0,0 +1,52 @@
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+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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+From: Omar Sandoval <[email protected]>
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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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+
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+The following cleanup commit:
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+
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+ 50816c48997a ("sched/wait: Standardize internal naming of wait-queue entries")
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+
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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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+
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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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+
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+Signed-off-by: Omar Sandoval <[email protected]>
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+Reviewed-by: Jens Axboe <[email protected]>
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+Acked-by: Peter Zijlstra <[email protected]>
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+Cc: Linus Torvalds <[email protected]>
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+Cc: Thomas Gleixner <[email protected]>
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+Cc: [email protected]
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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 <[email protected]>
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+(cherry picked from commit c6b9d9a33029014446bd9ed84c1688f6d3d4eab9)
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+Signed-off-by: Fabian Grünbichler <[email protected]>
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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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+
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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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+
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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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+
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Fabian Grünbichler