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Subject: Re: [PATCH] mm/page_counter: fix various data races
To:     Qian Cai <cai@lca.pw>
Cc:     Dmitry Vyukov <dvyukov@google.com>,
        Michal Hocko <mhocko@kernel.org>, akpm@linux-foundation.org,
        hannes@cmpxchg.org, elver@google.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <59f892d0-5fc4-ae32-ce65-5a688d9180c8@I-love.SAKURA.ne.jp>
 <2D795DB7-66FE-4F01-872F-F8ACAE9505EF@lca.pw>
From:   Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Message-ID: <d98acf1e-ef0a-035f-2d7c-e22bc4c874bd@i-love.sakura.ne.jp>
Date:   Wed, 29 Jan 2020 22:09:29 +0900
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On 2020/01/29 21:25, Qian Cai wrote:
> 
> 
>> On Jan 29, 2020, at 7:13 AM, Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp> wrote:
>>
>> By the way, can READ_ONCE()/WRITE_ONCE() really solve this warning?
>> The link above says read/write on the same location ( mm/page_counter.c:129 ).
>> I don't know how READ_ONCE()/WRITE_ONCE() can solve the race.
> 
> That looks like a different one where it complains about c->failcnt++. I’ll send a separate patch for that.
> 

Ah, then this patch is meant for mm/page_counter.c:138 versus page_counter.c:139 race which was
closed as invalid at https://syzkaller.appspot.com/bug?id=871391ec080746185a2dd437c54d75fcd1ef0ef8 .