On 2017/9/26 下午2:39, 박병철/선임연구원/SW Platform(연)AOT팀(byungchul.park@xxxxxxx) wrote: >> -----Original Message----- >> From: Michael Lyle [mailto:mlyle@xxxxxxxx] >> Sent: Tuesday, September 26, 2017 1:38 PM >> To: Coly Li >> Cc: linux-bcache@xxxxxxxxxxxxxxx; linux-block@xxxxxxxxxxxxxxx; >> axboe@xxxxxxxxx; 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
