Commit 18f85699 authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Restructure dispatch_to_local_dsq() 



Now that there's nothing left after the big if block, flip the if condition
and unindent the body.

No functional changes intended.

v2: Add BUG() to clarify control can't reach the end of
    dispatch_to_local_dsq() in UP kernels per David.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarDavid Vernet <void@manifault.com>
parent 0aab2630

kernel/sched/ext.c

+46 −50
Original line number Diff line number Diff line
@@ -2402,18 +2402,21 @@ static void dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq, 
	}



#ifdef CONFIG_SMP

	if (likely(task_can_run_on_remote_rq(p, dst_rq, true))) {

	if (unlikely(!task_can_run_on_remote_rq(p, dst_rq, true))) {

		dispatch_enqueue(&scx_dsq_global, p, enq_flags | SCX_ENQ_CLEAR_OPSS);

		return;

	}



	/*

		 * @p is on a possibly remote @src_rq which we need to lock to

		 * move the task. If dequeue is in progress, it'd be locking

		 * @src_rq and waiting on DISPATCHING, so we can't grab @src_rq

		 * lock while holding DISPATCHING.

	 * @p is on a possibly remote @src_rq which we need to lock to move the

	 * task. If dequeue is in progress, it'd be locking @src_rq and waiting

	 * on DISPATCHING, so we can't grab @src_rq lock while holding

	 * DISPATCHING.

	 *

		 * As DISPATCHING guarantees that @p is wholly ours, we can

		 * pretend that we're moving from a DSQ and use the same

		 * mechanism - mark the task under transfer with holding_cpu,

		 * release DISPATCHING and then follow the same protocol. See

		 * unlink_dsq_and_lock_src_rq().

	 * As DISPATCHING guarantees that @p is wholly ours, we can pretend that

	 * we're moving from a DSQ and use the same mechanism - mark the task

	 * under transfer with holding_cpu, release DISPATCHING and then follow

	 * the same protocol. See unlink_dsq_and_lock_src_rq().

	 */

	p->scx.holding_cpu = raw_smp_processor_id();
@@ -2430,23 +2433,19 @@ static void dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq, 
	if (likely(p->scx.holding_cpu == raw_smp_processor_id()) &&

	    !WARN_ON_ONCE(src_rq != task_rq(p))) {

		/*

			 * If @p is staying on the same rq, there's no need to

			 * go through the full deactivate/activate cycle.

			 * Optimize by abbreviating the operations in

			 * move_task_to_local_dsq().

		 * If @p is staying on the same rq, there's no need to go

		 * through the full deactivate/activate cycle. Optimize by

		 * abbreviating the operations in move_task_to_local_dsq().

		 */

		if (src_rq == dst_rq) {

			p->scx.holding_cpu = -1;

				dispatch_enqueue(&dst_rq->scx.local_dsq,

						 p, enq_flags);

			dispatch_enqueue(&dst_rq->scx.local_dsq, p, enq_flags);

		} else {

				move_task_to_local_dsq(p, enq_flags,

						       src_rq, dst_rq);

			move_task_to_local_dsq(p, enq_flags, src_rq, dst_rq);

		}



		/* if the destination CPU is idle, wake it up */

			if (sched_class_above(p->sched_class,

					      dst_rq->curr->sched_class))

		if (sched_class_above(p->sched_class, dst_rq->curr->sched_class))

			resched_curr(dst_rq);

	}
@@ -2455,12 +2454,9 @@ static void dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq, 
		raw_spin_rq_unlock(dst_rq);

		raw_spin_rq_lock(rq);

	}



		return;

	}

#else	/* CONFIG_SMP */

	BUG();	/* control can not reach here on UP */

#endif	/* CONFIG_SMP */



	dispatch_enqueue(&scx_dsq_global, p, enq_flags | SCX_ENQ_CLEAR_OPSS);

}



/**