Re: [PATCH v2] mm/page_alloc: fix potential deadlock on zonelist_update_seq seqlock

Michal Hocko
2023-04-05T08:28:13Z

On Tue 04-04-23 14:25:28, Andrew Morton wrote:
> On Tue, 4 Apr 2023 23:31:58 +0900 Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> wrote:
>
> > syzbot is reporting circular locking dependency which involves
> > zonelist_update_seq seqlock [1], for this lock is checked by memory
> > allocation requests which do not need to be retried.
>
> I queued this, along with a note that an updated changelog is likely.
>
> Do we feel that a -stable backport is warranted? I think so, from your
> earlier comments. Please add the cc:stable to the changelog in this
> situation.

Memory hotplug is pretty rare event so the deadlock is quite unlikely.
On the other hand the fix is pretty easy so it shouldn't hurt to have it
in stable kernels.

--
Michal Hocko
SUSE Labs