sched: Guarantee task priority in pick_next_task() (37e117c0) · Commits · e / devices / android_kernel_fairphone_FP4

kernel/sched/core.c

+8 −4

Original line number	Original line	Diff line number	Diff line
	@@ -2586,25 +2586,29 @@ static inline void schedule_debug(struct task_struct *prev)
	static inline struct task_struct *		static inline struct task_struct *
	pick_next_task(struct rq rq, struct task_struct prev)		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;		struct task_struct *p;

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

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

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

+12 −1

Original line number	Original line	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 cfs_rq *cfs_rq = &rq->cfs;
	struct sched_entity *se;		struct sched_entity *se;
	struct task_struct *p;		struct task_struct *p;
			int new_tasks;

	again:		again:
	#ifdef CONFIG_FAIR_GROUP_SCHED		#ifdef CONFIG_FAIR_GROUP_SCHED
	@@ -4784,7 +4785,17 @@ pick_next_task_fair(struct rq rq, struct task_struct prev)
	return p;		return p;

	idle:		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;		goto again;

	return NULL;		return NULL;

+9 −1

Original line number	Original line	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 task_struct *p;
	struct rt_rq *rt_rq = &rq->rt;		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(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)		if (!rt_rq->rt_nr_running)
	return NULL;		return NULL;

+5 −0

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

	#define DEQUEUE_SLEEP 1		#define DEQUEUE_SLEEP 1

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

	struct sched_class {		struct sched_class {
	const struct sched_class *next;		const struct sched_class *next;

	@@ -1105,6 +1107,9 @@ struct sched_class {
	* It is the responsibility of the pick_next_task() method that will		* 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		* return the next task to call put_prev_task() on the @prev task or
	* something equivalent.		* 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 * (pick_next_task) (struct rq rq,
	struct task_struct *prev);		struct task_struct *prev);