linux-kernel - [PATCH] sched/deadline: always enqueue on previous rq when dl_task

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Message-Id: <1427792017-7356-1-git-send-email-juri.lelli@arm.com>
Date:	Tue, 31 Mar 2015 09:53:36 +0100
From:	Juri Lelli <juri.lelli@....com>
To:	peterz@...radead.org
Cc:	linux-kernel@...r.kernel.org, Juri Lelli <juri.lelli@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Kirill Tkhai <ktkhai@...allels.com>,
	Juri Lelli <juri.lelli@...il.com>
Subject: [PATCH] sched/deadline: always enqueue on previous rq when dl_task_timer fires

dl_task_timer() may fire on a different rq from where a task was removed
after throttling. Since the call path is:

  dl_task_timer() ->
    enqueue_task_dl() ->
      enqueue_dl_entity() ->
        replenish_dl_entity()

and replenish_dl_entity() uses dl_se's rq, we can't use current's rq
in dl_task_timer(), but we need to lock the task's previous one.

Signed-off-by: Juri Lelli <juri.lelli@....com>
Tested-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
Acked-by: Kirill Tkhai <ktkhai@...allels.com>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Kirill Tkhai <ktkhai@...allels.com>
Cc: Juri Lelli <juri.lelli@...il.com>
Cc: linux-kernel@...r.kernel.org
Fixes: 3960c8c0c789 ("sched: Make dl_task_time() use task_rq_lock()")
---
 kernel/sched/deadline.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 3fa8fa6..f670cbb 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -514,7 +514,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
 	unsigned long flags;
 	struct rq *rq;
 
-	rq = task_rq_lock(current, &flags);
+	rq = task_rq_lock(p, &flags);
 
 	/*
 	 * We need to take care of several possible races here:
@@ -569,7 +569,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
 		push_dl_task(rq);
 #endif
 unlock:
-	task_rq_unlock(rq, current, &flags);
+	task_rq_unlock(rq, p, &flags);
 
 	return HRTIMER_NORESTART;
 }
-- 
2.2.2

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