linux-kernel - [PATCH] sched: fix rt_nr_migratory corruption raised in push_rt

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Date:	Mon, 30 May 2011 21:39:50 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Mike Galbraith <efault@....de>,
	Yong Zhang <yong.zhang0@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: [PATCH] sched: fix rt_nr_migratory corruption raised in push_rt_task()

When pushing, if a pushable task could not be pushed, it is dequeued with no
updating the rt_nr_migratory element of RT run-queue, then rt_nr_migratory is
corrupted, which is fixed by removing the dequeue operation.

Signed-off-by: Hillf Danton <dhillf@...il.com>
---
 kernel/sched_rt.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index 88725c9..496e06a 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -1378,6 +1378,7 @@ static int push_rt_task(struct rq *rq)
 {
 	struct task_struct *next_task;
 	struct rq *lowest_rq;
+	int ret = 1;

 	if (!rq->rt.overloaded)
 		return 0;
@@ -1425,7 +1426,7 @@ retry:
 			 * since the other cpus will pull from us when they
 			 * are ready.
 			 */
-			dequeue_pushable_task(rq, next_task);
+			ret = 0;
 			goto out;
 		}

@@ -1452,7 +1453,7 @@ retry:
 out:
 	put_task_struct(next_task);

-	return 1;
+	return ret;
 }

 static void push_rt_tasks(struct rq *rq)
--
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