[PATCH 5/6] sched: Fix broken assertion

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

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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@chello.nl>
LKML-Reference: <new-submission>
---
 kernel/sched.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -2041,7 +2041,8 @@ void set_task_cpu(struct task_struct *p,
 	 * 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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