Re: [PATCH 04/12] bcache: Don't reinvent the wheel but use existing llist API

Michael Lyle
2017-09-26T19:55:55Z

Thanks everyone--

Yes, this looks good to me and works in testing.

Mike

On Tue, Sep 26, 2017 at 12:46 AM, Coly Li <i@coly.li> wrote:
> On 2017/9/26 下午12:38, Michael Lyle wrote:
>> I believe this introduces a critical bug.
>>
>> cl->list is used to link together the llists for both things waiting,
>> and for things that are being woken.
>>
>> If a closure that is woken decides to wait again, it will corrupt the
>> llist that __closure_wake_up is using.
>>
>> The previous iteration structure gets the next element of the list
>> before waking and is therefore safe.
>
>
> Hi Michael and Byungchul,
>
> This is my fault to suggest Byungchul to change his correct patch into
> wrong one. But it's good to learn such an implicit race behind bcache
> code. I just post a patch to explain how this race may happen and
> corrupt the reverse list iteration. Could you please to review the fix ?
>
> And thanks to Michael again to catch this bug.
>
> --
> Coly Li