linux-kernel - Re: [PATCH -next] memcg: don't handle event

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <29aae825-6a1c-1935-a50f-d824c308c4c9@huawei.com>
Date: Wed, 15 May 2024 10:45:04 +0800
From: xiujianfeng <xiujianfeng@...wei.com>
To: Michal Hocko <mhocko@...e.com>
CC: <hannes@...xchg.org>, <roman.gushchin@...ux.dev>,
	<shakeel.butt@...ux.dev>, <muchun.song@...ux.dev>,
	<akpm@...ux-foundation.org>, <cgroups@...r.kernel.org>, <linux-mm@...ck.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH -next] memcg: don't handle event_list for v2 when
 offlining



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 <xiujianfeng@...wei.com>
>> ---
>>  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
>