Commit 7b3d61f6 authored by John Stultz's avatar John Stultz Committed by Peter Zijlstra
Browse files

sched: Split out __schedule() deactivate task logic into a helper 



As we're going to re-use the deactivation logic,
split it into a helper.

Signed-off-by: default avatarJohn Stultz <jstultz@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarMetin Kaya <metin.kaya@arm.com>
Reviewed-by: default avatarQais Yousef <qyousef@layalina.io>
Tested-by: default avatarK Prateek Nayak <kprateek.nayak@amd.com>
Tested-by: default avatarMetin Kaya <metin.kaya@arm.com>
Link: https://lore.kernel.org/r/20241009235352.1614323-7-jstultz@google.com
parent 18adad1d

kernel/sched/core.c

+40 −27
Original line number Diff line number Diff line
@@ -6490,6 +6490,45 @@ pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) 
#define SM_PREEMPT		1

#define SM_RTLOCK_WAIT		2



/*

 * Helper function for __schedule()

 *

 * If a task does not have signals pending, deactivate it

 * Otherwise marks the task's __state as RUNNING

 */

static bool try_to_block_task(struct rq *rq, struct task_struct *p,

			      unsigned long task_state)

{

	int flags = DEQUEUE_NOCLOCK;



	if (signal_pending_state(task_state, p)) {

		WRITE_ONCE(p->__state, TASK_RUNNING);

		return false;

	}



	p->sched_contributes_to_load =

		(task_state & TASK_UNINTERRUPTIBLE) &&

		!(task_state & TASK_NOLOAD) &&

		!(task_state & TASK_FROZEN);



	if (unlikely(is_special_task_state(task_state)))

		flags |= DEQUEUE_SPECIAL;



	/*

	 * __schedule()			ttwu()

	 *   prev_state = prev->state;    if (p->on_rq && ...)

	 *   if (prev_state)		    goto out;

	 *     p->on_rq = 0;		  smp_acquire__after_ctrl_dep();

	 *				  p->state = TASK_WAKING

	 *

	 * Where __schedule() and ttwu() have matching control dependencies.

	 *

	 * After this, schedule() must not care about p->state any more.

	 */

	block_task(rq, p, flags);

	return true;

}



/*

 * __schedule() is the main scheduler function.

 *
@@ -6598,33 +6637,7 @@ static void __sched notrace __schedule(int sched_mode) 
			goto picked;

		}

	} else if (!preempt && prev_state) {

		if (signal_pending_state(prev_state, prev)) {

			WRITE_ONCE(prev->__state, TASK_RUNNING);

		} else {

			int flags = DEQUEUE_NOCLOCK;



			prev->sched_contributes_to_load =

				(prev_state & TASK_UNINTERRUPTIBLE) &&

				!(prev_state & TASK_NOLOAD) &&

				!(prev_state & TASK_FROZEN);



			if (unlikely(is_special_task_state(prev_state)))

				flags |= DEQUEUE_SPECIAL;



			/*

			 * __schedule()			ttwu()

			 *   prev_state = prev->state;    if (p->on_rq && ...)

			 *   if (prev_state)		    goto out;

			 *     p->on_rq = 0;		  smp_acquire__after_ctrl_dep();

			 *				  p->state = TASK_WAKING

			 *

			 * Where __schedule() and ttwu() have matching control dependencies.

			 *

			 * After this, schedule() must not care about p->state any more.

			 */

			block_task(rq, prev, flags);

			block = true;

		}

		block = try_to_block_task(rq, prev, prev_state);

		switch_count = &prev->nvcsw;

	}