linux-kernel - [tip:sched/urgent] sched: Fix broken assertion

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Date:	Thu, 17 Dec 2009 12:31:52 GMT
From:	tip-bot for Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...hat.com,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, mingo@...e.hu
Subject: [tip:sched/urgent] sched: Fix broken assertion

Commit-ID:  077614ee1e93245a3b9a4e1213659405dbeb0ba6
Gitweb:     http://git.kernel.org/tip/077614ee1e93245a3b9a4e1213659405dbeb0ba6
Author:     Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Thu, 17 Dec 2009 13:16:31 +0100
Committer:  Ingo Molnar <mingo@...e.hu>
CommitDate: Thu, 17 Dec 2009 13:22:46 +0100

sched: Fix broken assertion

There's a preemption race in the set_task_cpu() debug check in
that when we get preempted after setting task->state we'd still
be on the rq proper, but fail the test.

Check for preempted tasks, since those are always on the RQ.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
LKML-Reference: <20091217121830.137155561@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
 kernel/sched.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 7be88a7..720df10 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2041,7 +2041,8 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
 	 * We should never call set_task_cpu() on a blocked task,
 	 * ttwu() will sort out the placement.
 	 */
-	WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING);
+	WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
+			!(task_thread_info(p)->preempt_count & PREEMPT_ACTIVE));
 #endif
 
 	trace_sched_migrate_task(p, new_cpu);
--
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