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

Coly Li
2017-09-26T07:09:25Z

On 2017/9/26 下午2:39, 박병철/선임연구원/SW
Platform(연)AOT팀(byungchul.park@lge.com) wrote:
>> -----Original Message-----
>> From: Michael Lyle [mailto:mlyle@lyle.org]
>> Sent: Tuesday, September 26, 2017 1:38 PM
>> To: Coly Li
>> Cc: linux-bcache@vger.kernel.org; linux-block@vger.kernel.org;
>> axboe@kernel.dk; Eric Wheeler; Byungchul Park; Kent Overstreet
>> Subject: Re: [PATCH 04/12] bcache: Don't reinvent the wheel but use existing
>> llist API
>>
>> 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.
>
> Do you mean we have to use llist_for_each_entry_safe() instead of non-safe version?
> Is it ok if we use it instead?

Yes, we should use llist_for_each_entry_safe(), there is a quite
implicit race here.

--
Coly Li