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McKenney" , Andrew Morton , JP Kobryn , Johannes Weiner , Ying Huang , Vlastimil Babka , Alexei Starovoitov , Sebastian Andrzej Siewior , Michal =?iso-8859-1?Q?Koutn=FD?= , bpf@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team Subject: Re: [PATCH] llist: add [READ|WRITE]_ONCE tags for llist_node Message-ID: References: <20250626190550.4170599-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 2EFFF140017 X-Rspam-User: X-Rspamd-Server: rspam06 X-Stat-Signature: 8g85eb91ddpshhmtqcti9rqhwsifihn4 X-HE-Tag: 1750983331-387594 X-HE-Meta: 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 bWs5yvhw SnKf4qByOHDvpB1vBel5ukAPsfvQUZxz7YAUOakbl892NCZDijXAP2dv35+xnBftlhWY5xWZXiIoCnrAW/gXSOko3EdBGMT6FH/2DmIGYf3V7kFYJaw8SKN2up/i0OcM9bfByow0YMC169VKHgRL0RZ3A9Fm/vQc2yk0GmmHzGX8XSaP/i1rB6EvqeGvRqV7AJVIJcIR5ih4xbz7mJCB+nWJzDmNr1OiT6Dl+kyhTyy5CwPSjZLA8B1ldOUv6d8ZA6DRy0AOTcmS2/gGeOWgOf/C3wnqhwqx6EmRsjSobqzoConA= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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