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[tip:sched/urgent] sched/core: Add missing lockdep_unpin() annotations

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Commit-ID:  0aaafaabfcba8aa991913cd3280a5dbf7f111a2a
Gitweb:     http://git.kernel.org/tip/0aaafaabfcba8aa991913cd3280a5dbf7f111a2a
Author:     Peter Zijlstra <peterz@infradead.org>
AuthorDate: Fri, 23 Oct 2015 11:50:08 +0200
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 23 Oct 2015 12:02:10 +0200

sched/core: Add missing lockdep_unpin() annotations

Luca and Wanpeng reported two missing annotations that led to
false lockdep complaints. Add the missing annotations.

Reported-by: Luca Abeni <luca.abeni@unitn.it>
Reported-by: Wanpeng Li <wanpeng.li@hotmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: cbce1a686700 ("sched,lockdep: Employ lock pinning")
Link: http://lkml.kernel.org/r/20151023095008.GY17308@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 kernel/sched/core.c     | 9 ++++++++-
 kernel/sched/deadline.c | 9 ++++++++-
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 5bd7d60..bcd214e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2366,8 +2366,15 @@ void wake_up_new_task(struct task_struct *p)
 	trace_sched_wakeup_new(p);
 	check_preempt_curr(rq, p, WF_FORK);
 #ifdef CONFIG_SMP
-	if (p->sched_class->task_woken)
+	if (p->sched_class->task_woken) {
+		/*
+		 * Nothing relies on rq->lock after this, so its fine to
+		 * drop it.
+		 */
+		lockdep_unpin_lock(&rq->lock);
 		p->sched_class->task_woken(rq, p);
+		lockdep_pin_lock(&rq->lock);
+	}
 #endif
 	task_rq_unlock(rq, p, &flags);
 }
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 142df26..8b0a15e 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -668,8 +668,15 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
 	 * Queueing this task back might have overloaded rq, check if we need
 	 * to kick someone away.
 	 */
-	if (has_pushable_dl_tasks(rq))
+	if (has_pushable_dl_tasks(rq)) {
+		/*
+		 * Nothing relies on rq->lock after this, so its safe to drop
+		 * rq->lock.
+		 */
+		lockdep_unpin_lock(&rq->lock);
 		push_dl_task(rq);
+		lockdep_pin_lock(&rq->lock);
+	}
 #endif
 
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Thread

lockdep-related warning in  kernel/sched/deadline.c::find_lock_later_rq() Luca Abeni <luca.abeni@unitn.it> - 2015-10-21 15:30 +0200
  Re: lockdep-related warning in  kernel/sched/deadline.c::find_lock_later_rq() Wanpeng Li <wanpeng.li@hotmail.com> - 2015-10-22 07:40 +0200
    Re: lockdep-related warning in  kernel/sched/deadline.c::find_lock_later_rq() Luca Abeni <luca.abeni@unitn.it> - 2015-10-22 09:10 +0200
      Re: lockdep-related warning in  kernel/sched/deadline.c::find_lock_later_rq() Peter Zijlstra <peterz@infradead.org> - 2015-10-23 12:00 +0200
        [tip:sched/urgent] sched/core: Add missing lockdep_unpin()   annotations tip-bot for Peter Zijlstra <tipbot@zytor.com> - 2015-10-23 12:10 +0200
        Re: lockdep-related warning in  kernel/sched/deadline.c::find_lock_later_rq() Luca Abeni <luca.abeni@unitn.it> - 2015-10-23 22:20 +0200

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