linux-kernel - [PATCH RT 1/4] sched: ttwu: Return success when only changing the saved

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Date:	Tue, 17 Jan 2012 22:45:32 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org,
	linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Carsten Emde <C.Emde@...dl.org>,
	John Kacur <jkacur@...hat.com>, stable-rt@...r.kernel.org
Subject: [PATCH RT 1/4] sched: ttwu: Return success when only changing the saved_state value

From: Thomas Gleixner <tglx@...utronix.de>

When a task blocks on a rt lock, it saves the current state in
p->saved_state, so a lock related wake up will not destroy the
original state.

When a real wakeup happens, while the task is running due to a lock
wakeup already, we update p->saved_state to TASK_RUNNING, but we do
not return success, which might cause another wakeup in the waitqueue
code and the task remains in the waitqueue list. Return success in
that case as well.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: stable-rt@...r.kernel.org
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/sched.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 63aeba0..e5ef7a8 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2693,8 +2693,10 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags)
 		 * if the wakeup condition is true.
 		 */
 		if (!(wake_flags & WF_LOCK_SLEEPER)) {
-			if (p->saved_state & state)
+			if (p->saved_state & state) {
 				p->saved_state = TASK_RUNNING;
+				success = 1;
+			}
 		}
 		goto out;
 	}
-- 
1.7.8.3



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