diff options
| -rw-r--r-- | kernel/sched/core.c | 4 | ||||
| -rw-r--r-- | kernel/sched/deadline.c | 34 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 5 |
3 files changed, 36 insertions, 7 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 0cd34e68680c..379cb87da69d 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1008,6 +1008,9 @@ inline int task_curr(const struct task_struct *p) return cpu_curr(task_cpu(p)) == p; } +/* + * Can drop rq->lock because from sched_class::switched_from() methods drop it. + */ static inline void check_class_changed(struct rq *rq, struct task_struct *p, const struct sched_class *prev_class, int oldprio) @@ -1015,6 +1018,7 @@ static inline void check_class_changed(struct rq *rq, struct task_struct *p, if (prev_class != p->sched_class) { if (prev_class->switched_from) prev_class->switched_from(rq, p); + /* Possble rq->lock 'hole'. */ p->sched_class->switched_to(rq, p); } else if (oldprio != p->prio || dl_task(p)) p->sched_class->prio_changed(rq, p, oldprio); diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 2e31a30e623c..9d483e862e58 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -563,11 +563,6 @@ void init_dl_task_timer(struct sched_dl_entity *dl_se) { struct hrtimer *timer = &dl_se->dl_timer; - if (hrtimer_active(timer)) { - hrtimer_try_to_cancel(timer); - return; - } - hrtimer_init(timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); timer->function = dl_task_timer; } @@ -1610,10 +1605,35 @@ void init_sched_dl_class(void) #endif /* CONFIG_SMP */ +/* + * Ensure p's dl_timer is cancelled. May drop rq->lock for a while. + */ +static void cancel_dl_timer(struct rq *rq, struct task_struct *p) +{ + struct hrtimer *dl_timer = &p->dl.dl_timer; + + /* Nobody will change task's class if pi_lock is held */ + lockdep_assert_held(&p->pi_lock); + + if (hrtimer_active(dl_timer)) { + int ret = hrtimer_try_to_cancel(dl_timer); + + if (unlikely(ret == -1)) { + /* + * Note, p may migrate OR new deadline tasks + * may appear in rq when we are unlocking it. + * A caller of us must be fine with that. + */ + raw_spin_unlock(&rq->lock); + hrtimer_cancel(dl_timer); + raw_spin_lock(&rq->lock); + } + } +} + static void switched_from_dl(struct rq *rq, struct task_struct *p) { - if (hrtimer_active(&p->dl.dl_timer) && !dl_policy(p->policy)) - hrtimer_try_to_cancel(&p->dl.dl_timer); + cancel_dl_timer(rq, p); __dl_clear_params(p); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index ec3917c5f898..49b941fe2cc2 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1157,6 +1157,11 @@ struct sched_class { void (*task_fork) (struct task_struct *p); void (*task_dead) (struct task_struct *p); + /* + * The switched_from() call is allowed to drop rq->lock, therefore we + * cannot assume the switched_from/switched_to pair is serliazed by + * rq->lock. They are however serialized by p->pi_lock. + */ void (*switched_from) (struct rq *this_rq, struct task_struct *task); void (*switched_to) (struct rq *this_rq, struct task_struct *task); void (*prio_changed) (struct rq *this_rq, struct task_struct *task, |