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Tue, 14 May 2024 14:10:00 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id Sg2vGbhwQ2Z6NwAAD6G6ig (envelope-from ); Tue, 14 May 2024 14:10:00 +0000 Date: Tue, 14 May 2024 16:09:58 +0200 From: Michal Hocko To: Xiu Jianfeng Cc: hannes@cmpxchg.org, roman.gushchin@linux.dev, shakeel.butt@linux.dev, muchun.song@linux.dev, akpm@linux-foundation.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -next] memcg: don't handle event_list for v2 when offlining Message-ID: References: <20240514131106.1326323-1-xiujianfeng@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240514131106.1326323-1-xiujianfeng@huawei.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 90638180021 X-Stat-Signature: tphwu5ujywxygbf4cyi9dyf7e9kk6kio X-HE-Tag: 1715695802-892033 X-HE-Meta: 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 KredavIU xvpYHbCb6KM1aw2qfTMoJzyxhaft38U+K1ZRoLk6WPuyrqOAXS2/pBhLBePEhKGuM5j9UqtsZ1BFyb3YbCdLc1OfUx0SVMlpilqW9HeOSYWZqrwD7L05HMpIAoGSMqEf93/jKFAYW3BufZXyomdTzq3UAXE7Zo2/JP98O85et4Yd/xHk9h1oMYclu8pkgLZBSkCfO/jGSXpfXj63IxdF2V4w5DpAZiUaLxOgr7LBewqClYI3g0pLaDQlq7e4059NDWfb80Ehp5UX4p8zrRtPCH0P3UqtJlMkW16nx 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: On Tue 14-05-24 13:11:06, Xiu Jianfeng wrote: > The event_list for memcg is only valid for v1 and not used for v2, > so it's unnessesary to handle event_list for v2. You are right but the code as is works just fine. The list will be empty. It is true that we do not need to take event_list_lock lock but nobody should be using this lock anyway. Also the offline callback is not particularly hot path. So why do we want to change the code? > > Signed-off-by: Xiu Jianfeng > --- > mm/memcontrol.c | 12 +++++++----- > 1 file changed, 7 insertions(+), 5 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index d127c9c5fabf..4254f9cd05f4 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -5881,12 +5881,14 @@ static void mem_cgroup_css_offline(struct cgroup_subsys_state *css) > * Notify userspace about cgroup removing only after rmdir of cgroup > * directory to avoid race between userspace and kernelspace. > */ > - spin_lock_irq(&memcg->event_list_lock); > - list_for_each_entry_safe(event, tmp, &memcg->event_list, list) { > - list_del_init(&event->list); > - schedule_work(&event->remove); > + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys)) { > + spin_lock_irq(&memcg->event_list_lock); > + list_for_each_entry_safe(event, tmp, &memcg->event_list, list) { > + list_del_init(&event->list); > + schedule_work(&event->remove); > + } > + spin_unlock_irq(&memcg->event_list_lock); > } > - spin_unlock_irq(&memcg->event_list_lock); > > page_counter_set_min(&memcg->memory, 0); > page_counter_set_low(&memcg->memory, 0); > -- > 2.34.1 -- Michal Hocko SUSE Labs