Re: [syzbot] [cgroups?] [mm?] WARNING in __mod_memcg_lruvec_state

Yu Zhao
2024-04-05T01:44:57Z

On Thu, Apr 4, 2024 at 7:36 PM Yosry Ahmed <yosryahmed@google.com> wrote:
>
> On Wed, Apr 3, 2024 at 6:08 PM Andrew Morton <akpm@linux-foundation.org> wrote:
> >
> > On Tue, 02 Apr 2024 01:03:26 -0700 syzbot <syzbot+9319a4268a640e26b72b@syzkaller.appspotmail.com> wrote:
> >
> > > Hello,
> > >
> > > syzbot found the following issue on:
> > >
> > > HEAD commit: 317c7bc0ef03 Merge tag 'mmc-v6.9-rc1' of git://git.kernel...
> > > git tree: upstream
> > > console output: https://syzkaller.appspot.com/x/log.txt?x=15fd40c5180000
> > > kernel config: https://syzkaller.appspot.com/x/.config?x=f64ec427e98bccd7
> > > dashboard link: https://syzkaller.appspot.com/bug?extid=9319a4268a640e26b72b
> > > compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > >
> > > Unfortunately, I don't have any reproducer for this issue yet.
> > >
> > > Downloadable assets:
> > > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-317c7bc0.raw.xz
> > > vmlinux: https://storage.googleapis.com/syzbot-assets/efab473d72c0/vmlinux-317c7bc0.xz
> > > kernel image: https://storage.googleapis.com/syzbot-assets/5ba3f56d362d/bzImage-317c7bc0.xz
> > >
> > > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > > Reported-by: syzbot+9319a4268a640e26b72b@syzkaller.appspotmail.com
> > >
> > > ------------[ cut here ]------------
> > > WARNING: CPU: 0 PID: 30105 at mm/memcontrol.c:865 __mod_memcg_lruvec_state+0x3fa/0x550 mm/memcontrol.c:865
> > > Modules linked in:
> > > CPU: 0 PID: 30105 Comm: syz-executor.2 Not tainted 6.9.0-rc1-syzkaller-00178-g317c7bc0ef03 #0
> > > Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
> > > RIP: 0010:__mod_memcg_lruvec_state+0x3fa/0x550 mm/memcontrol.c:865
> > > Code: 45 85 e4 75 1d 48 83 c4 18 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc b8 00 04 00 00 e9 80 fd ff ff 89 c6 e9 a0 fd ff ff 90 <0f> 0b 90 e9 a7 fc ff ff 48 c7 c7 18 43 e1 8f e8 32 51 f8 ff e9 5e
> > > RSP: 0018:ffffc900034beef8 EFLAGS: 00010202
> > > RAX: 0000000000000292 RBX: 0000000000000001 RCX: 1ffffffff1fc2863
> > > RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff888024b92bc8
> > > RBP: ffff888024b92000 R08: 0000000000000005 R09: 0000000000000000
> > > R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001
> > > R13: ffff88801c326000 R14: 0000000000000001 R15: ffff888024b92000
> > > FS: 00007f0811bf96c0(0000) GS:ffff88806b000000(0000) knlGS:0000000000000000
> > > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > > CR2: 000000000cfff1dd CR3: 000000003e4e2000 CR4: 0000000000350ef0
> > > DR0: 0000000000000031 DR1: 0000000000000000 DR2: 0000000000000000
> > > DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> > > Call Trace:
> > > <TASK>
> > > __update_lru_size include/linux/mm_inline.h:47 [inline]
> > > lru_gen_update_size include/linux/mm_inline.h:199 [inline]
> > > lru_gen_add_folio+0x62d/0xe80 include/linux/mm_inline.h:262
> > > lruvec_add_folio include/linux/mm_inline.h:323 [inline]
> > > lru_add_fn+0x3fc/0xd80 mm/swap.c:215
> > > folio_batch_move_lru+0x243/0x400 mm/swap.c:233
> >
> > Well it beats me. I assume we failed to update for a new case. I'll
> > toss this into -next to perhaps shed a bit of light.
> >
> > --- a/mm/memcontrol.c~__mod_memcg_lruvec_state-enhance-diagnostics
> > +++ a/mm/memcontrol.c
> > @@ -860,10 +860,12 @@ void __mod_memcg_lruvec_state(struct lru
> > case NR_ANON_THPS:
> > case NR_SHMEM_PMDMAPPED:
> > case NR_FILE_PMDMAPPED:
> > - WARN_ON_ONCE(!in_task());
> > + if (WARN_ON_ONCE(!in_task()))
> > + pr_warn("stat item index: %d\n", idx);
> > break;
> > default:
> > - VM_WARN_ON_IRQS_ENABLED();
> > + if (VM_WARN_ON_IRQS_ENABLED())
> > + pr_warn("stat item index: %d\n", idx);
>
> Line 865 from this commit should be this warning (i.e. warning because
> IRQs are enabled). This also makes sense because __update_lru_size()
> should not be updating any of the above stats.
>
> folio_batch_move_lru() in the above call stack should be acquiring the
> lock with IRQs disabled though, so I am not sure what's going on from
> a quick look.
>
> Adding Yu Zhao here.

Probably an RT build where _irqsave doesn't disable IRQ?