From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 82AF09460; Fri, 27 Jun 2025 00:15:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750983330; cv=none; b=qZkHJCiVOgajLCtyJR/s3qsEDJgYjPs3UkBWAF8X9Ue4BVBFW9bgm1lTdvvH5nz3ijlCk6UVYvat6g0DoykoPSGYPaElxCVLk33P2k1JspGGVCSitCLLtnzWLtA4uIse4qpyTiKnWfqhcHGJeSDrUvbFBzGDm5MnsU9JebrM4F0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750983330; c=relaxed/simple; bh=m945KNlyWYf0qERzTab94sokctIlIGpySTIYEKVfQzw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EGCnCFcHMub5aX6qa1lvIsv9J0AQcJoWGYIHjW0cGr1hRJGhClGW12ao3AsHsUhUZOZ1X5BMr0KnDEWah6I4wkNb07Ftaajqtl1+Gm5ye1u9Q86Wt9RHlefcC/KYn9+JZmSUScTl8N7NMuflw7W0rogKrKDjmoQTXDAVV8rYRBU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kr7Ib40r; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kr7Ib40r" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D17A3C4CEEB; Fri, 27 Jun 2025 00:15:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750983330; bh=m945KNlyWYf0qERzTab94sokctIlIGpySTIYEKVfQzw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=kr7Ib40rXKzOfbtpOqTWk9H9JSFObuOi9Ec+z059VOSTkYmi1AivcRjSyMIaMdn66 +ZHuP9iKnzV+TSucZtWy7hdMSjaO+mxiDbliqh1SOYybiJyIR4xlHYdMHL0WCCizFA wGthh9jhYPB9alBN0zhcKc6/NgEPfQ42pllSbve8U/nB/6zm+6bI2gMt8gXmK0P9dC P7fT5E1cZgkmG+xa+SyLp9fRVgXyLwGw474Iqrx7nh9MGmZQSR0nZoqg5FXjDtHgKt XmbP+ghaSoiILCroptjomvtLpiB7CoIqOlElo2r6jmdcSFV2NAau+TnBuzrXjxGbLL D5sGuaEYbdQVw== Date: Thu, 26 Jun 2025 14:15:28 -1000 From: Tejun Heo To: Shakeel Butt Cc: "Paul E . 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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