linux-kernel - Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list

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Message-ID: <20200106012034.GA15705@richard>
Date:   Mon, 6 Jan 2020 09:20:34 +0800
From:   Wei Yang <richardw.yang@...ux.intel.com>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Wei Yang <richardw.yang@...ux.intel.com>, hannes@...xchg.org,
        mhocko@...nel.org, vdavydov.dev@...il.com,
        akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, yang.shi@...ux.alibaba.com
Subject: Re: [RFC PATCH] mm: thp: grab the lock before manipulation defer list

On Fri, Jan 03, 2020 at 04:44:59PM -0800, David Rientjes wrote:
>On Sat, 4 Jan 2020, Wei Yang wrote:
>
>> On Fri, Jan 03, 2020 at 11:29:06AM -0800, David Rientjes wrote:
>> >On Fri, 3 Jan 2020, Wei Yang wrote:
>> >
>> >> As all the other places, we grab the lock before manipulate the defer list.
>> >> Current implementation may face a race condition.
>> >> 
>> >> Fixes: 87eaceb3faa5 ("mm: thp: make deferred split shrinker memcg aware")
>> >> 
>> >> Signed-off-by: Wei Yang <richardw.yang@...ux.intel.com>
>> >> 
>> >> ---
>> >> I notice the difference during code reading and just confused about the
>> >> difference. No specific test is done since limited knowledge about cgroup.
>> >> 
>> >> Maybe I miss something important?
>> >
>> >The check for !list_empty(page_deferred_list(page)) must certainly be 
>> >serialized with doing list_del_init(page_deferred_list(page)).
>> >
>> 
>> Hi David
>> 
>> Would you mind giving more information? You mean list_empty and list_del_init
>> is atomic?
>> 
>
>I mean your patch is obviously correct :)  It should likely also have a 
>stable@...r.kernel.org # 5.4+

Ah, my poor English ;-)

>
>Acked-by: David Rientjes <rientjes@...gle.com>

-- 
Wei Yang
Help you, Help me