[tip:sched/core] sched/deadline: Always enqueue on previous rq when dl_task_timer() fires

From: tip-bot for Juri Lelli
Date: Thu Apr 02 2015 - 14:47:35 EST

Commit-ID: 4cd57f97135840f637431c92380c8da3edbe44ed
Gitweb: http://git.kernel.org/tip/4cd57f97135840f637431c92380c8da3edbe44ed
Author: Juri Lelli <juri.lelli@xxxxxxx>
AuthorDate: Tue, 31 Mar 2015 09:53:36 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 2 Apr 2015 17:42:56 +0200

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() ->

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@xxxxxxxxxxxxxxx>
Signed-off-by: Juri Lelli <juri.lelli@xxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Kirill Tkhai <ktkhai@xxxxxxxxxxxxx>
Cc: Juri Lelli <juri.lelli@xxxxxxxxx>
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@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
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 5e2f99b..9d3ad64 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)
- task_rq_unlock(rq, current, &flags);
+ task_rq_unlock(rq, p, &flags);

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