sched_ext: Refactor do_enqueue_task() local and global DSQ paths

[ Upstream commit 3546119 ]

The local and global DSQ enqueue paths in do_enqueue_task() share the same
slice refill logic. Factor out the common code into a shared enqueue label.
This makes adding new enqueue cases easier. No functional changes.

Reviewed-by: Andrea Righi <arighi@nvidia.com>
Reviewed-by: Emil Tsalapatis <emil@etsalapatis.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Stable-dep-of: 7e0ffb7 ("sched_ext: Fix stale direct dispatch state in ddsp_dsq_id")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: htejun

kernel/sched/ext.c

@@ -1243,6 +1243,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
 {
 	struct scx_sched *sch = scx_root;
 	struct task_struct **ddsp_taskp;
+	struct scx_dispatch_q *dsq;
 	unsigned long qseq;
 
 	WARN_ON_ONCE(!(p->scx.flags & SCX_TASK_QUEUED));
@@ -1310,23 +1311,25 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
 direct:
 	direct_dispatch(sch, p, enq_flags);
 	return;
-
+local_norefill:
+	dispatch_enqueue(sch, &rq->scx.local_dsq, p, enq_flags);
+	return;
 local:
+	dsq = &rq->scx.local_dsq;
+	goto enqueue;
+global:
+	dsq = find_global_dsq(sch, p);
+	goto enqueue;
+
+enqueue:
 	/*
 	 * For task-ordering, slice refill must be treated as implying the end
 	 * of the current slice. Otherwise, the longer @p stays on the CPU, the
 	 * higher priority it becomes from scx_prio_less()'s POV.
 	 */
 	touch_core_sched(rq, p);
 	refill_task_slice_dfl(sch, p);
-local_norefill:
-	dispatch_enqueue(sch, &rq->scx.local_dsq, p, enq_flags);
-	return;
-
-global:
-	touch_core_sched(rq, p);	/* see the comment in local: */
-	refill_task_slice_dfl(sch, p);
-	dispatch_enqueue(sch, find_global_dsq(sch, p), p, enq_flags);
+	dispatch_enqueue(sch, dsq, p, enq_flags);
 }
 
 static bool task_runnable(const struct task_struct *p)