Commit d18b96ce authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Factor out abbreviated dispatch dequeue into dispatch_dequeue_locked() 



move_task_between_dsqs() contains open-coded abbreviated dequeue logic when
moving tasks between non-local DSQs. Factor this out into
dispatch_dequeue_locked() which can be used when both the task's rq and dsq
locks are already held. Add lockdep assertions to both dispatch_dequeue() and
the new helper to verify locking requirements.

This prepares for the load balancer which will need the same abbreviated
dequeue pattern.

Cc: Andrea Righi <arighi@nvidia.com>
Cc: Dan Schatzberg <schatzberg.dan@gmail.com>
Cc: Emil Tsalapatis <etsal@meta.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent d2974cc7

kernel/sched/ext.c

+17 −2
Original line number Diff line number Diff line
@@ -1106,6 +1106,8 @@ static void dispatch_dequeue(struct rq *rq, struct task_struct *p) 
	struct scx_dispatch_q *dsq = p->scx.dsq;

	bool is_local = dsq == &rq->scx.local_dsq;



	lockdep_assert_rq_held(rq);



	if (!dsq) {

		/*

		 * If !dsq && on-list, @p is on @rq's ddsp_deferred_locals.
@@ -1152,6 +1154,20 @@ static void dispatch_dequeue(struct rq *rq, struct task_struct *p) 
		raw_spin_unlock(&dsq->lock);

}



/*

 * Abbreviated version of dispatch_dequeue() that can be used when both @p's rq

 * and dsq are locked.

 */

static void dispatch_dequeue_locked(struct task_struct *p,

				    struct scx_dispatch_q *dsq)

{

	lockdep_assert_rq_held(task_rq(p));

	lockdep_assert_held(&dsq->lock);



	task_unlink_from_dsq(p, dsq);

	p->scx.dsq = NULL;

}



static struct scx_dispatch_q *find_dsq_for_dispatch(struct scx_sched *sch,

						    struct rq *rq, u64 dsq_id,

						    struct task_struct *p)
@@ -1812,8 +1828,7 @@ static struct rq *move_task_between_dsqs(struct scx_sched *sch, 
		 * @p is going from a non-local DSQ to a non-local DSQ. As

		 * $src_dsq is already locked, do an abbreviated dequeue.

		 */

		task_unlink_from_dsq(p, src_dsq);

		p->scx.dsq = NULL;

		dispatch_dequeue_locked(p, src_dsq);

		raw_spin_unlock(&src_dsq->lock);



		dispatch_enqueue(sch, dst_dsq, p, enq_flags);