Commit 0aab2630 authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Fix processs_ddsp_deferred_locals() by unifying DTL_INVALID handling 



With the preceding update, the only return value which makes meaningful
difference is DTL_INVALID, for which one caller, finish_dispatch(), falls
back to the global DSQ and the other, process_ddsp_deferred_locals(),
doesn't do anything.

It should always fallback to the global DSQ. Move the global DSQ fallback
into dispatch_to_local_dsq() and remove the return value.

v2: Patch title and description updated to reflect the behavior fix for
    process_ddsp_deferred_locals().

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarDavid Vernet <void@manifault.com>
parent e683949a

kernel/sched/ext.c

+10 −31
Original line number Diff line number Diff line
@@ -2370,12 +2370,6 @@ static bool consume_dispatch_q(struct rq *rq, struct scx_dispatch_q *dsq) 
	return false;

}



enum dispatch_to_local_dsq_ret {

	DTL_DISPATCHED,		/* successfully dispatched */

	DTL_LOST,		/* lost race to dequeue */

	DTL_INVALID,		/* invalid local dsq_id */

};



/**

 * dispatch_to_local_dsq - Dispatch a task to a local dsq

 * @rq: current rq which is locked
@@ -2390,8 +2384,7 @@ enum dispatch_to_local_dsq_ret { 
 * The caller must have exclusive ownership of @p (e.g. through

 * %SCX_OPSS_DISPATCHING).

 */

static enum dispatch_to_local_dsq_ret

dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq,

static void dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq,

				  struct task_struct *p, u64 enq_flags)

{

	struct rq *src_rq = task_rq(p);
@@ -2405,13 +2398,11 @@ dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq, 
	 */

	if (rq == src_rq && rq == dst_rq) {

		dispatch_enqueue(dst_dsq, p, enq_flags | SCX_ENQ_CLEAR_OPSS);

		return DTL_DISPATCHED;

		return;

	}



#ifdef CONFIG_SMP

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

		bool dsp;



		/*

		 * @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
@@ -2436,10 +2427,8 @@ dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq, 
		}



		/* task_rq couldn't have changed if we're still the holding cpu */

		dsp = p->scx.holding_cpu == raw_smp_processor_id() &&

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



		if (likely(dsp)) {

		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.
@@ -2467,11 +2456,11 @@ dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_dsq, 
			raw_spin_rq_lock(rq);

		}



		return dsp ? DTL_DISPATCHED : DTL_LOST;

		return;

	}

#endif	/* CONFIG_SMP */



	return DTL_INVALID;

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

}



/**
@@ -2548,21 +2537,11 @@ static void finish_dispatch(struct rq *rq, struct task_struct *p, 


	dsq = find_dsq_for_dispatch(this_rq(), dsq_id, p);



	if (dsq->id == SCX_DSQ_LOCAL) {

		switch (dispatch_to_local_dsq(rq, dsq, p, enq_flags)) {

		case DTL_DISPATCHED:

			break;

		case DTL_LOST:

			break;

		case DTL_INVALID:

			dispatch_enqueue(&scx_dsq_global, p,

					 enq_flags | SCX_ENQ_CLEAR_OPSS);

			break;

		}

	} else {

	if (dsq->id == SCX_DSQ_LOCAL)

		dispatch_to_local_dsq(rq, dsq, p, enq_flags);

	else

		dispatch_enqueue(dsq, p, enq_flags | SCX_ENQ_CLEAR_OPSS);

}

}



static void flush_dispatch_buf(struct rq *rq)

{