From 5bfd126e80dca70431aef8fdbc1cf14535f3c338 Mon Sep 17 00:00:00 2001 From: Juri Lelli Date: Tue, 15 Apr 2014 13:49:04 +0200 Subject: [PATCH] sched/deadline: Fix sched_yield() behavior yield_task_dl() is broken: o it forces current to be throttled setting its runtime to zero; o it sets current's dl_se->dl_new to one, expecting that dl_task_timer() will queue it back with proper parameters at replenish time. Unfortunately, dl_task_timer() has this check at the very beginning: if (!dl_task(p) || dl_se->dl_new) goto unlock; So, it just bails out and the task is never replenished. It actually yielded forever. To fix this, introduce a new flag indicating that the task properly yielded the CPU before its current runtime expired. While this is a little overdoing at the moment, the flag would be useful in the future to discriminate between "good" jobs (of which remaining runtime could be reclaimed, i.e. recycled) and "bad" jobs (for which dl_throttled task has been set) that needed to be stopped. Reported-by: yjay.kim Signed-off-by: Juri Lelli Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/20140429103953.e68eba1b2ac3309214e3dc5a@gmail.com Signed-off-by: Ingo Molnar --- include/linux/sched.h | 7 +++++-- kernel/sched/core.c | 1 + kernel/sched/deadline.c | 5 +++-- 3 files changed, 9 insertions(+), 4 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 25f54c79f757..2a4298fb0d85 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1153,9 +1153,12 @@ struct sched_dl_entity { * * @dl_boosted tells if we are boosted due to DI. If so we are * outside bandwidth enforcement mechanism (but only until we - * exit the critical section). + * exit the critical section); + * + * @dl_yielded tells if task gave up the cpu before consuming + * all its available runtime during the last job. */ - int dl_throttled, dl_new, dl_boosted; + int dl_throttled, dl_new, dl_boosted, dl_yielded; /* * Bandwidth enforcement timer. Each -deadline task has its diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9fe2190005cb..e62c65a12d5b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3124,6 +3124,7 @@ __setparam_dl(struct task_struct *p, const struct sched_attr *attr) dl_se->dl_bw = to_ratio(dl_se->dl_period, dl_se->dl_runtime); dl_se->dl_throttled = 0; dl_se->dl_new = 1; + dl_se->dl_yielded = 0; } static void __setscheduler_params(struct task_struct *p, diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index b08095786cb8..800e99b99075 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -528,6 +528,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer) sched_clock_tick(); update_rq_clock(rq); dl_se->dl_throttled = 0; + dl_se->dl_yielded = 0; if (p->on_rq) { enqueue_task_dl(rq, p, ENQUEUE_REPLENISH); if (task_has_dl_policy(rq->curr)) @@ -893,10 +894,10 @@ static void yield_task_dl(struct rq *rq) * We make the task go to sleep until its current deadline by * forcing its runtime to zero. This way, update_curr_dl() stops * it and the bandwidth timer will wake it up and will give it - * new scheduling parameters (thanks to dl_new=1). + * new scheduling parameters (thanks to dl_yielded=1). */ if (p->dl.runtime > 0) { - rq->curr->dl.dl_new = 1; + rq->curr->dl.dl_yielded = 1; p->dl.runtime = 0; } update_curr_dl(rq);