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>

1 files changed, 19 insertions, 19 deletions

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 7b684f9341a5..a027799ae130 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);