linux-kernel - [PATCH 4.0 207/220] sched/deadline: Always enqueue on previous rq when dl_task

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Message-Id: <20150502185903.216058575@linuxfoundation.org>
Date:	Sat,  2 May 2015 21:02:02 +0200
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Juri Lelli <juri.lelli@....com>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>,
	Kirill Tkhai <ktkhai@...allels.com>,
	Juri Lelli <juri.lelli@...il.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: [PATCH 4.0 207/220] sched/deadline: Always enqueue on previous rq when dl_task_timer() fires

4.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Juri Lelli <juri.lelli@....com>

commit 4cd57f97135840f637431c92380c8da3edbe44ed upstream.

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.

Tested-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
Signed-off-by: Juri Lelli <juri.lelli@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Kirill Tkhai <ktkhai@...allels.com>
Cc: Juri Lelli <juri.lelli@...il.com>
Fixes: 3960c8c0c789 ("sched: Make dl_task_time() use task_rq_lock()")
Link: http://lkml.kernel.org/r/1427792017-7356-1-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 kernel/sched/deadline.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -514,7 +514,7 @@ static enum hrtimer_restart dl_task_time
 	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_time
 		push_dl_task(rq);
 #endif
 unlock:
-	task_rq_unlock(rq, current, &flags);
+	task_rq_unlock(rq, p, &flags);
 
 	return HRTIMER_NORESTART;
 }


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