sched_ext: Replace consume_local_task() with move_local_task_to_local_dsq()

- 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>
Acked-by: David Vernet <void@manifault.com>

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index baed98c0ceb3ba7eefee9cfd74cd91358f6b2f71..cfb41328588217f984f93f3b81189df23938da7b 100644 (file)
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -2172,23 +2172,30 @@ 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
@@ -2196,8 +2203,8 @@ 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);
 
@@ -2320,7 +2327,7 @@ static bool consume_remote_task(struct rq *this_rq, struct task_struct *p,
        raw_spin_rq_unlock(this_rq);
 
        if (unlink_dsq_and_lock_src_rq(p, dsq, src_rq)) {
-               move_task_to_local_dsq(p, 0, src_rq, this_rq);
+               move_remote_task_to_local_dsq(p, 0, src_rq, this_rq);
                return true;
        } else {
                raw_spin_rq_unlock(src_rq);
@@ -2351,7 +2358,9 @@ retry:
                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;
                }
 
@@ -2431,13 +2440,14 @@ 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 */