linux-kernel - [PATCH 2.6.32 21/42] sched/core: Remove false-positive warning from wake_up

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Date:	Sat, 23 Jan 2016 15:12:42 +0100
From:	Willy Tarreau <w@....eu>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Mike Galbraith <efault@....de>,
	Thomas Gleixner <tglx@...utronix.de>, oleg@...hat.com,
	Ingo Molnar <mingo@...nel.org>,
	Ben Hutchings <ben@...adent.org.uk>, Willy Tarreau <w@....eu>
Subject: [PATCH 2.6.32 21/42] sched/core: Remove false-positive warning from
 wake_up_process()

2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------

From: Sasha Levin <sasha.levin@...cle.com>

commit 119d6f6a3be8b424b200dcee56e74484d5445f7e upstream.

Because wakeups can (fundamentally) be late, a task might not be in
the expected state. Therefore testing against a task's state is racy,
and can yield false positives.

Signed-off-by: Sasha Levin <sasha.levin@...cle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: oleg@...hat.com
Fixes: 9067ac85d533 ("wake_up_process() should be never used to wakeup a TASK_STOPPED/TRACED task")
Link: http://lkml.kernel.org/r/1448933660-23082-1-git-send-email-sasha.levin@oracle.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
[bwh: Backported to 3.2: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
(cherry picked from commit 0e796c1b57fdd97fc040b0b78ff7fea6c0a4a39d)
Signed-off-by: Willy Tarreau <w@....eu>
---
 kernel/sched.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 42bf6a6..fe26b86 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2618,7 +2618,6 @@ out:
  */
 int wake_up_process(struct task_struct *p)
 {
-	WARN_ON(task_is_stopped_or_traced(p));
 	return try_to_wake_up(p, TASK_NORMAL, 0);
 }
 EXPORT_SYMBOL(wake_up_process);
-- 
1.7.12.2.21.g234cd45.dirty