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Subject[tip:sched/core] sched/deadline: Fix stale yield state
Commit-ID:  1019a359d3dc4b64d0e1e5a5efcb725d5e83994d
Gitweb: http://git.kernel.org/tip/1019a359d3dc4b64d0e1e5a5efcb725d5e83994d
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Wed, 26 Nov 2014 08:44:03 +0800
Committer: Ingo Molnar <mingo@kernel.org>
CommitDate: Wed, 4 Feb 2015 07:52:26 +0100

sched/deadline: Fix stale yield state

When we fail to start the deadline timer in update_curr_dl(), we
forget to clear ->dl_yielded, resulting in wrecked time keeping.

Since the natural place to clear both ->dl_yielded and ->dl_throttled
is in replenish_dl_entity(); both are after all waiting for that event;
make it so.

Luckily since 67dfa1b756f2 ("sched/deadline: Implement
cancel_dl_timer() to use in switched_from_dl()") the
task_on_rq_queued() condition in dl_task_timer() must be true, and can
therefore call enqueue_task_dl() unconditionally.

Reported-by: Wanpeng Li <wanpeng.li@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Kirill Tkhai <ktkhai@parallels.com>
Cc: Juri Lelli <juri.lelli@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1416962647-76792-4-git-send-email-wanpeng.li@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/sched/deadline.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 7b684f9..a027799 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -350,6 +350,11 @@ static void replenish_dl_entity(struct sched_dl_entity *dl_se,
dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline;
dl_se->runtime = pi_se->dl_runtime;
}
+
+ if (dl_se->dl_yielded)
+ dl_se->dl_yielded = 0;
+ if (dl_se->dl_throttled)
+ dl_se->dl_throttled = 0;
}

/*
@@ -536,23 +541,19 @@ again:

sched_clock_tick();
update_rq_clock(rq);
- dl_se->dl_throttled = 0;
- dl_se->dl_yielded = 0;
- if (task_on_rq_queued(p)) {
- enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
- if (dl_task(rq->curr))
- check_preempt_curr_dl(rq, p, 0);
- else
- resched_curr(rq);
+ enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
+ if (dl_task(rq->curr))
+ check_preempt_curr_dl(rq, p, 0);
+ else
+ resched_curr(rq);
#ifdef CONFIG_SMP
- /*
- * Queueing this task back might have overloaded rq,
- * check if we need to kick someone away.
- */
- if (has_pushable_dl_tasks(rq))
- push_dl_task(rq);
+ /*
+ * Queueing this task back might have overloaded rq,
+ * check if we need to kick someone away.
+ */
+ if (has_pushable_dl_tasks(rq))
+ push_dl_task(rq);
#endif
- }
unlock:
raw_spin_unlock(&rq->lock);

@@ -613,10 +614,9 @@ static void update_curr_dl(struct rq *rq)

dl_se->runtime -= dl_se->dl_yielded ? 0 : delta_exec;
if (dl_runtime_exceeded(rq, dl_se)) {
+ dl_se->dl_throttled = 1;
__dequeue_task_dl(rq, curr, 0);
- if (likely(start_dl_timer(dl_se, curr->dl.dl_boosted)))
- dl_se->dl_throttled = 1;
- else
+ if (unlikely(!start_dl_timer(dl_se, curr->dl.dl_boosted)))
enqueue_task_dl(rq, curr, ENQUEUE_REPLENISH);

if (!is_leftmost(curr, &rq->dl))
@@ -853,7 +853,7 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
* its rq, the bandwidth timer callback (which clearly has not
* run yet) will take care of this.
*/
- if (p->dl.dl_throttled)
+ if (p->dl.dl_throttled && !(flags & ENQUEUE_REPLENISH))
return;

enqueue_dl_entity(&p->dl, pi_se, flags);

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