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Subject[tip:sched/urgent] sched: Fix broken assertion
Commit-ID:  077614ee1e93245a3b9a4e1213659405dbeb0ba6
Gitweb: http://git.kernel.org/tip/077614ee1e93245a3b9a4e1213659405dbeb0ba6
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Thu, 17 Dec 2009 13:16:31 +0100
Committer: Ingo Molnar <mingo@elte.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@chello.nl>
LKML-Reference: <20091217121830.137155561@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.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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