[PATCH 05/11] sched_ext: Restructure dispatch_to_local_dsq()

Tejun Heo
2024-08-30T11:04:30Z

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

No functional changes intended.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/sched/ext.c | 94 ++++++++++++++++++++++------------------------
1 file changed, 44 insertions(+), 50 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 34b4e63850c1..add267f31396 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -2333,65 +2333,59 @@ 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))) {
- /*
- * @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_task_rq().
- */
- p->scx.holding_cpu = raw_smp_processor_id();
+ 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;
+ }

- /* store_release ensures that dequeue sees the above */
- atomic_long_set_release(&p->scx.ops_state, SCX_OPSS_NONE);
+ /*
+ * @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_task_rq().
+ */
+ p->scx.holding_cpu = raw_smp_processor_id();

- /* switch to @src_rq lock */
- if (rq != src_rq) {
- raw_spin_rq_unlock(rq);
- raw_spin_rq_lock(src_rq);
- }
+ /* store_release ensures that dequeue sees the above */
+ atomic_long_set_release(&p->scx.ops_state, SCX_OPSS_NONE);

- /* task_rq couldn't have changed if we're still the holding cpu */
- 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 (src_rq == dst_rq) {
- p->scx.holding_cpu = -1;
- dispatch_enqueue(&dst_rq->scx.local_dsq,
- p, enq_flags);
- } else {
- move_task_to_local_dsq(p, enq_flags,
- src_rq, dst_rq);
- }
+ /* switch to @src_rq lock */
+ if (rq != src_rq) {
+ raw_spin_rq_unlock(rq);
+ raw_spin_rq_lock(src_rq);
+ }

- /* if the destination CPU is idle, wake it up */
- if (sched_class_above(p->sched_class,
- dst_rq->curr->sched_class))
- resched_curr(dst_rq);
+ /* task_rq couldn't have changed if we're still the holding cpu */
+ 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 (src_rq == dst_rq) {
+ p->scx.holding_cpu = -1;
+ dispatch_enqueue(&dst_rq->scx.local_dsq, p, enq_flags);
+ } else {
+ move_task_to_local_dsq(p, enq_flags, src_rq, dst_rq);
}

- /* switch back to @rq lock */
- if (rq != dst_rq) {
- raw_spin_rq_unlock(dst_rq);
- raw_spin_rq_lock(rq);
- }
+ /* if the destination CPU is idle, wake it up */
+ if (sched_class_above(p->sched_class, dst_rq->curr->sched_class))
+ resched_curr(dst_rq);
+ }

- return;
+ /* switch back to @rq lock */
+ if (rq != dst_rq) {
+ raw_spin_rq_unlock(dst_rq);
+ raw_spin_rq_lock(rq);
}
#endif /* CONFIG_SMP */
-
- dispatch_enqueue(&scx_dsq_global, p, enq_flags | SCX_ENQ_CLEAR_OPSS);
}

/**
--
2.46.0