sched: Guarantee task priority in pick_next_task() (37e117c0) · Commits · 戴 / test

kernel/sched/core.c

+8 −4

Original line number	Diff line number	Diff line
		@@ -2586,25 +2586,29 @@ static inline void schedule_debug(struct task_struct *prev)
		static inline struct task_struct *
		pick_next_task(struct rq rq, struct task_struct prev)
		{
		const struct sched_class *class;
		const struct sched_class *class = &fair_sched_class;
		struct task_struct *p;

		/*
		* Optimization: we know that if all tasks are in
		* the fair class we can call that function directly:
		*/
		if (likely(prev->sched_class == &fair_sched_class &&
		if (likely(prev->sched_class == class &&
		rq->nr_running == rq->cfs.h_nr_running)) {
		p = fair_sched_class.pick_next_task(rq, prev);
		if (likely(p))
		if (likely(p && p != RETRY_TASK))
		return p;
		}

		again:
		for_each_class(class) {
		p = class->pick_next_task(rq, prev);
		if (p)
		if (p) {
		if (unlikely(p == RETRY_TASK))
		goto again;
		return p;
		}
		}

		BUG(); /* the idle class will always have a runnable task */
		}

+12 −1

Original line number	Diff line number	Diff line
		@@ -4686,6 +4686,7 @@ pick_next_task_fair(struct rq rq, struct task_struct prev)
		struct cfs_rq *cfs_rq = &rq->cfs;
		struct sched_entity *se;
		struct task_struct *p;
		int new_tasks;

		again:
		#ifdef CONFIG_FAIR_GROUP_SCHED
		@@ -4784,7 +4785,17 @@ simple:
		return p;

		idle:
		if (idle_balance(rq)) /* drops rq->lock */
		/*
		* Because idle_balance() releases (and re-acquires) rq->lock, it is
		* possible for any higher priority task to appear. In that case we
		* must re-start the pick_next_entity() loop.
		*/
		new_tasks = idle_balance(rq);

		if (rq->nr_running != rq->cfs.h_nr_running)
		return RETRY_TASK;

		if (new_tasks)
		goto again;

		return NULL;

+9 −1

Original line number	Diff line number	Diff line
		@@ -1360,8 +1360,16 @@ pick_next_task_rt(struct rq rq, struct task_struct prev)
		struct task_struct *p;
		struct rt_rq *rt_rq = &rq->rt;

		if (need_pull_rt_task(rq, prev))
		if (need_pull_rt_task(rq, prev)) {
		pull_rt_task(rq);
		/*
		* pull_rt_task() can drop (and re-acquire) rq->lock; this
		* means a dl task can slip in, in which case we need to
		* re-start task selection.
		*/
		if (unlikely(rq->dl.dl_nr_running))
		return RETRY_TASK;
		}

		if (!rt_rq->rt_nr_running)
		return NULL;

+5 −0

Original line number	Diff line number	Diff line
		@@ -1091,6 +1091,8 @@ static const u32 prio_to_wmult[40] = {

		#define DEQUEUE_SLEEP 1

		#define RETRY_TASK ((void *)-1UL)

		struct sched_class {
		const struct sched_class *next;

		@@ -1105,6 +1107,9 @@ struct sched_class {
		* It is the responsibility of the pick_next_task() method that will
		* return the next task to call put_prev_task() on the @prev task or
		* something equivalent.
		*
		* May return RETRY_TASK when it finds a higher prio class has runnable
		* tasks.
		*/
		struct task_struct * (pick_next_task) (struct rq rq,
		struct task_struct *prev);