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Wed, 15 May 2024 10:45:04 +0800 Message-ID: <29aae825-6a1c-1935-a50f-d824c308c4c9@huawei.com> Date: Wed, 15 May 2024 10:45:04 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH -next] memcg: don't handle event_list for v2 when offlining To: Michal Hocko CC: , , , , , , , References: <20240514131106.1326323-1-xiujianfeng@huawei.com> Content-Language: en-US From: xiujianfeng In-Reply-To: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.110.112] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggpeml500023.china.huawei.com (7.185.36.114) X-Rspamd-Queue-Id: E67D1140007 X-Stat-Signature: 7oa6x5eunju7jz66rzqdf63zsx1o3btn X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1715741108-313501 X-HE-Meta: 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 CuhiUA1v lS8TS/Yl4/7VbV8NFeZ56AZ0Z74OBazHQLKhbhnzJynvkafn9FTxzd722s6SaLjml4uwSYrzQCdPSccxFzTCqm3qnTwzkNx9w2yCe30CNTWu1ib6s+J4rh9gDrJhts6I3U/0pDvVTVpxsw8fCKIqiRoempcJ3C8XeE1uZuJdj4LlFCjsT3czC/3eFFxIaF/sW0/UQwfe+iwisBhmhJKhtPouE9H4Cn1P8hvkB 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 2024/5/14 22:09, Michal Hocko wrote: > 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? > Actually, I don’t quite agree, but I don't insist on this patch. Thanks for your feedback. >> >> 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 >