linux-kernel - [PATCH] scx: set p->scx.ops_state using atomic_long_set

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Date:   Thu,  7 Dec 2023 11:04:59 +0900
From:   Changwoo Min <multics69@...il.com>
To:     tj@...nel.org
Cc:     kernel-dev@...lia.com, andrea.righi@...onical.com,
        andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
        brho@...gle.com, bristot@...hat.com, bsegall@...gle.com,
        changwoo@...lia.com, daniel@...earbox.net, derkling@...gle.com,
        dietmar.eggemann@....com, dschatzberg@...a.com,
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        himadrics@...ia.fr, joshdon@...gle.com, juri.lelli@...hat.com,
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        martin.lau@...nel.org, memxor@...il.com, mgorman@...e.de,
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        riel@...riel.com, rostedt@...dmis.org,
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        vschneid@...hat.com
Subject: [PATCH] scx: set p->scx.ops_state using atomic_long_set_release

p->scx.ops_state should be updated using the release semantics,
atomic_long_set_release(), because it is read using
atomic_long_read_acquire() at ops_dequeue() and wait_ops_state().
---
 kernel/sched/ext.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
index 53ee906aa2b6..3a40ca2007b6 100644
--- a/kernel/sched/ext.c
+++ b/kernel/sched/ext.c
@@ -881,7 +881,7 @@ static void do_enqueue_task(struct rq *rq, struct task_struct *p, u64 enq_flags,
 	qseq = rq->scx.ops_qseq++ << SCX_OPSS_QSEQ_SHIFT;
 
 	WARN_ON_ONCE(atomic_long_read(&p->scx.ops_state) != SCX_OPSS_NONE);
-	atomic_long_set(&p->scx.ops_state, SCX_OPSS_QUEUEING | qseq);
+	atomic_long_set_release(&p->scx.ops_state, SCX_OPSS_QUEUEING | qseq);
 
 	ddsp_taskp = this_cpu_ptr(&direct_dispatch_task);
 	WARN_ON_ONCE(*ddsp_taskp);
-- 
2.43.0