From: Tejun Heo <tj@kernel.org>
To: Shakeel Butt <shakeel.butt@linux.dev>
Cc: "Paul E . McKenney" <paulmck@kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
"JP Kobryn" <inwardvessel@gmail.com>,
"Johannes Weiner" <hannes@cmpxchg.org>,
"Ying Huang" <huang.ying.caritas@gmail.com>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Alexei Starovoitov" <ast@kernel.org>,
"Sebastian Andrzej Siewior" <bigeasy@linutronix.de>,
"Michal Koutný" <mkoutny@suse.com>,
bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org,
"Meta kernel team" <kernel-team@meta.com>
Subject: Re: [PATCH] llist: add [READ|WRITE]_ONCE tags for llist_node
Date: Thu, 26 Jun 2025 14:15:28 -1000 [thread overview]
Message-ID: <aF3ioBE_HX2_s-_o@slm.duckdns.org> (raw)
In-Reply-To: <fyyks2xnzytr5hybzxeb4srrmrr64dxacwrcjd7v7anttjdy3s@hgp2s2th2t5m>
Hello,
On Thu, Jun 26, 2025 at 04:38:18PM -0700, Shakeel Butt wrote:
> diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c
> index c8a48cf83878..02258b43abb3 100644
> --- a/kernel/cgroup/rstat.c
> +++ b/kernel/cgroup/rstat.c
> @@ -86,8 +86,12 @@ __bpf_kfunc void css_rstat_updated(struct cgroup_subsys_state *css, int cpu)
> return;
>
> rstatc = css_rstat_cpu(css, cpu);
> - /* If already on list return. */
> - if (llist_on_list(&rstatc->lnode))
> + /*
> + * If already on list return.
> + *
> + * TODO: add detailed comment on the potential race.
> + */
> + if (data_race(llist_on_list(&rstatc->lnode)))
> return;
Yeah, also in the functdion comment, explain that if avoiding such races is
important enough to justify the overhead, the caller can put smp_mb() before
calling css_rstat_updated().
Thanks.
--
tejun
prev parent reply other threads:[~2025-06-27 0:15 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-26 19:05 Shakeel Butt
2025-06-26 23:38 ` Shakeel Butt
2025-06-27 0:15 ` Tejun Heo [this message]
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