Re: [syzbot] [mm?] [cgroups?] WARNING: bad unlock balance in lruvec_stat_mod_folio

[Shakeel Butt]

+Qi & Yosry

On Tue, Apr 07, 2026 at 10:53:24AM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    cc13002a9f98 Add linux-next specific files for 20260402
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10d8946a580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=4e6c8be618ab359
> dashboard link: https://syzkaller.appspot.com/bug?extid=1a3353a77896e73a8f53
> compiler:       Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
> 
> Unfortunately, I don't have any reproducer for this issue yet.

Let's wait for the reproducer. I can only think of cgroup_subsys_on_dfl() check
returning different value in get_non_dying_memcg_start() and
get_non_dying_memcg_end() to cause this uneven rcu unlock. However I can't think
why and how that can happen.