sched/deadline: Fix lock pinning warning during CPU hotplug
The following warning can be triggered by hot-unplugging the CPU on which an active SCHED_DEADLINE task is running on: WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:3531 lock_release+0x690/0x6a0 releasing a pinned lock Call Trace: dump_stack+0x99/0xd0 __warn+0xd1/0xf0 ? dl_task_timer+0x1a1/0x2b0 warn_slowpath_fmt+0x4f/0x60 ? sched_clock+0x13/0x20 lock_release+0x690/0x6a0 ? enqueue_pushable_dl_task+0x9b/0xa0 ? enqueue_task_dl+0x1ca/0x480 _raw_spin_unlock+0x1f/0x40 dl_task_timer+0x1a1/0x2b0 ? push_dl_task.part.31+0x190/0x190 WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:3649 lock_unpin_lock+0x181/0x1a0 unpinning an unpinned lock Call Trace: dump_stack+0x99/0xd0 __warn+0xd1/0xf0 warn_slowpath_fmt+0x4f/0x60 lock_unpin_lock+0x181/0x1a0 dl_task_timer+0x127/0x2b0 ? push_dl_task.part.31+0x190/0x190 As per the comment before this code, its safe to drop the RQ lock here, and since we (potentially) change rq, unpin and repin to avoid the splat. Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com> [ Rewrote changelog. ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@arm.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Luca Abeni <luca.abeni@unitn.it> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Link: http://lkml.kernel.org/r/1470274940-17976-1-git-send-email-wanpeng.li@hotmail.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -658,8 +658,11 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
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*
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* XXX figure out if select_task_rq_dl() deals with offline cpus.
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*/
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if (unlikely(!rq->online))
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if (unlikely(!rq->online)) {
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lockdep_unpin_lock(&rq->lock, rf.cookie);
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rq = dl_task_offline_migration(rq, p);
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rf.cookie = lockdep_pin_lock(&rq->lock);
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}
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/*
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* Queueing this task back might have overloaded rq, check if we need
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