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

Coly Li
2017-09-26T07:08:50Z

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 Mike,

Good catch! I see llist_del_all() but forget cl->list can be modified in
closure_wait(). Yes there is potential chance to mislead
llist_for_each_entry() to iterate wrong list.
llist_for_each_entry_safe() should be used here. I will send a fix to
Jens, hope to catch up 4.14 still.

Thanks!
--
Coly Li