[PATCH 09/11] sched_ext: Replace consume_local_task() with move_local_task_to_local_dsq()

Tejun Heo
2024-08-30T11:04:34Z

- Rename move_task_to_local_dsq() to move_remote_task_to_local_dsq().

- Rename consume_local_task() to move_local_task_to_local_dsq() and remove
task_unlink_from_dsq() and source DSQ unlocking from it.

This is to make the migration code easier to reuse.

No functional changes intended.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/sched/ext.c | 42 ++++++++++++++++++++++++++----------------
1 file changed, 26 insertions(+), 16 deletions(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 51d141602a11..df33524d68f3 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -2103,23 +2103,30 @@ static bool yield_to_task_scx(struct rq *rq, struct task_struct *to)
return false;
}

-static void consume_local_task(struct task_struct *p,
- struct scx_dispatch_q *dsq, struct rq *rq)
+static void move_local_task_to_local_dsq(struct task_struct *p, u64 enq_flags,
+ struct scx_dispatch_q *src_dsq,
+ struct rq *dst_rq)
{
- lockdep_assert_held(&dsq->lock); /* released on return */
+ struct scx_dispatch_q *dst_dsq = &dst_rq->scx.local_dsq;
+
+ /* @dsq is locked and @p is on @dst_rq */
+ lockdep_assert_held(&src_dsq->lock);
+ lockdep_assert_rq_held(dst_rq);

- /* @dsq is locked and @p is on this rq */
WARN_ON_ONCE(p->scx.holding_cpu >= 0);
- task_unlink_from_dsq(p, dsq);
- list_add_tail(&p->scx.dsq_list.node, &rq->scx.local_dsq.list);
- dsq_mod_nr(&rq->scx.local_dsq, 1);
- p->scx.dsq = &rq->scx.local_dsq;
- raw_spin_unlock(&dsq->lock);
+
+ if (enq_flags & (SCX_ENQ_HEAD | SCX_ENQ_PREEMPT))
+ list_add(&p->scx.dsq_list.node, &dst_dsq->list);
+ else
+ list_add_tail(&p->scx.dsq_list.node, &dst_dsq->list);
+
+ dsq_mod_nr(dst_dsq, 1);
+ p->scx.dsq = dst_dsq;
}

#ifdef CONFIG_SMP
/**
- * move_task_to_local_dsq - Move a task from a different rq to a local DSQ
+ * move_remote_task_to_local_dsq - Move a task from a foreign rq to a local DSQ
* @p: task to move
* @enq_flags: %SCX_ENQ_*
* @src_rq: rq to move the task from, locked on entry, released on return
@@ -2127,8 +2134,8 @@ static void consume_local_task(struct task_struct *p,
*
* Move @p which is currently on @src_rq to @dst_rq's local DSQ.
*/
-static void move_task_to_local_dsq(struct task_struct *p, u64 enq_flags,
- struct rq *src_rq, struct rq *dst_rq)
+static void move_remote_task_to_local_dsq(struct task_struct *p, u64 enq_flags,
+ struct rq *src_rq, struct rq *dst_rq)
{
lockdep_assert_rq_held(src_rq);

@@ -2251,7 +2258,7 @@ static bool consume_remote_task(struct rq *this_rq, struct task_struct *p,
raw_spin_rq_unlock(this_rq);

if (unlink_dsq_and_lock_task_rq(p, dsq, task_rq)) {
- move_task_to_local_dsq(p, 0, task_rq, this_rq);
+ move_remote_task_to_local_dsq(p, 0, task_rq, this_rq);
return true;
} else {
raw_spin_rq_unlock(task_rq);
@@ -2282,7 +2289,9 @@ static bool consume_dispatch_q(struct rq *rq, struct scx_dispatch_q *dsq)
struct rq *task_rq = task_rq(p);

if (rq == task_rq) {
- consume_local_task(p, dsq, rq);
+ task_unlink_from_dsq(p, dsq);
+ move_local_task_to_local_dsq(p, 0, dsq, rq);
+ raw_spin_unlock(&dsq->lock);
return true;
}

@@ -2362,13 +2371,14 @@ static void dispatch_to_local_dsq(struct rq *rq, struct scx_dispatch_q *dst_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().
+ * abbreviating move_remote_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);
+ move_remote_task_to_local_dsq(p, enq_flags,
+ src_rq, dst_rq);
}

/* if the destination CPU is idle, wake it up */
--
2.46.0