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From: Usama Arif <usama.arif@linux.dev>
To: arighi@nvidia.com, bpf@vger.kernel.org, bsegall@google.com,
	changwoo@igalia.com, dietmar.eggemann@arm.com, etsal@meta.com,
	juri.lelli@redhat.com, kprateek.nayak@amd.com,
	linux-kernel@vger.kernel.org, mgorman@suse.de, mingo@redhat.com,
	peterz@infradead.org, rostedt@goodmis.org,
	sched-ext@lists.linux.dev, tj@kernel.org,
	vincent.guittot@linaro.org, void@manifault.com,
	vschneid@redhat.com, yphbchou0911@gmail.com
Cc: Usama Arif <usama.arif@linux.dev>
Subject: [PATCH] sched_ext: Update scx_dispatch_dequeue() comments
Date: Wed, 23 Sep 2026 14:34:18 -0700	[thread overview]
Message-ID: <20260923213418.3197834-1-usama.arif@linux.dev> (raw)

Remote consumption now reaches the !dsq branch with holding_cpu set,
just like direct dispatch. Also, the dsq-present branch races with
unlink_dsq_and_switch_rq_lock(), not dispatch_to_local_dsq().

Update both comments to describe the current transfer paths. No
functional change.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Usama Arif <usama.arif@linux.dev>
---
 kernel/sched/ext/ext.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/kernel/sched/ext/ext.c b/kernel/sched/ext/ext.c
index 0135ff6824b03..f95d1cf8d3d1c 100644
--- a/kernel/sched/ext/ext.c
+++ b/kernel/sched/ext/ext.c
@@ -1832,10 +1832,9 @@ void scx_dispatch_dequeue(struct rq *rq, struct task_struct *p)
 			list_del_init(&p->scx.dsq_list.node);
 
 		/*
-		 * When dispatching directly from the BPF scheduler to a local
-		 * DSQ, the task isn't associated with any DSQ but
-		 * @p->scx.holding_cpu may be set under the protection of
-		 * %SCX_OPSS_DISPATCHING.
+		 * When moving a task to a local DSQ through either direct dispatch
+		 * or remote consumption, the task isn't associated with any DSQ but
+		 * @p->scx.holding_cpu may be set.
 		 */
 		if (p->scx.holding_cpu >= 0)
 			p->scx.holding_cpu = -1;
@@ -1855,9 +1854,9 @@ void scx_dispatch_dequeue(struct rq *rq, struct task_struct *p)
 		scx_task_unlink_from_dsq(p, dsq);
 	} else {
 		/*
-		 * We're racing against dispatch_to_local_dsq() which already
-		 * removed @p from @dsq and set @p->scx.holding_cpu. Clear the
-		 * holding_cpu which tells dispatch_to_local_dsq() that it lost
+		 * We're racing against unlink_dsq_and_switch_rq_lock(), which
+		 * already removed @p from @dsq and set @p->scx.holding_cpu. Clear
+		 * holding_cpu to tell unlink_dsq_and_switch_rq_lock() that it lost
 		 * the race.
 		 */
 		WARN_ON_ONCE(!list_empty(&p->scx.dsq_list.node));
-- 
2.53.0-Meta


             reply	other threads:[~2026-09-23 21:34 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-23 21:34 Usama Arif [this message]
2026-09-23 23:20 ` Tejun Heo

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