Message-ID: <CAKFNMonBntuJ4Z8_tXkfBLzU=4vYOEYHd3YqxC7yWTOwkw+ypg@mail.gmail.com>
Date: Mon, 19 Feb 2024 21:32:56 +0900
From: Ryusuke Konishi <konishi.ryusuke@...il.com>
To: syzbot <syzbot+c8166c541d3971bf6c87@...kaller.appspotmail.com>
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-nilfs@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [nilfs?] INFO: task hung in nilfs_segctor_thread (2)

On Mon, Feb 19, 2024 at 7:54 PM syzbot wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    f735966ee23c Merge branches 'for-next/reorg-va-space' and ..
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linuxgit for-kernelci
> console output: https://syzkaller.appspot.com/x/log.txt?x=12dbb3dc180000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d47605a39da2cf06
> dashboard link: https://syzkaller.appspot.com/bug?extid=c8166c541d3971bf6c87
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: arm64
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/bdea2316c4db/disk-f735966e.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/75ba7806a91c/vmlinux-f735966e.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/208f119d45ed/Image-f735966e.gz.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+c8166c541d3971bf6c87@...kaller.appspotmail.com
>
> INFO: task segctord:26558 blocked for more than 143 seconds.
>       Not tainted 6.8.0-rc3-syzkaller-gf735966ee23c #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:segctord        state:D stack:0     pid:26558 tgid:26558 ppid:2      flags:0x00000008
> Call trace:
>  __switch_to+0x314/0x560 arch/arm64/kernel/process.c:556
>  context_switch kernel/sched/core.c:5400 [inline]
>  __schedule+0x1498/0x24b4 kernel/sched/core.c:6727
>  __schedule_loop kernel/sched/core.c:6802 [inline]
>  schedule+0xb8/0x19c kernel/sched/core.c:6817
>  schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6874
>  rwsem_down_write_slowpath+0xcfc/0x1aa0 kernel/locking/rwsem.c:1178
>  __down_write_common kernel/locking/rwsem.c:1306 [inline]
>  __down_write kernel/locking/rwsem.c:1315 [inline]
>  down_write+0xb4/0xc0 kernel/locking/rwsem.c:1580
>  nilfs_transaction_lock+0x178/0x33c fs/nilfs2/segment.c:357
>  nilfs_segctor_thread_construct fs/nilfs2/segment.c:2523 [inline]
>  nilfs_segctor_thread+0x3cc/0xd78 fs/nilfs2/segment.c:2608
>  kthread+0x288/0x310 kernel/kthread.c:388
>  ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860
>
> Showing all locks held in the system:
> 1 lock held by khungtaskd/29:
>  #0: ffff80008ee43fc0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:297
> 2 locks held by getty/5931:
>  #0: ffff0000d82710a0 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
>  #1: ffff800093fe72f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41c/0x1228 drivers/tty/n_tty.c:2201
> 1 lock held by syz-executor.0/6205:
>  #0: ffff0000d6d12c68 (&pipe->mutex/1){+.+.}-{3:3}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:297
> 2 locks held by kworker/u4:26/13298:
> 6 locks held by syz-executor.2/26553:
> 1 lock held by segctord/26558:
>  #0: ffff00011fc2d2a0
>  (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_lock+0x178/0x33c fs/nilfs2/segment.c:357
> 1 lock held by syz-executor.3/11586:
>  #0: ffff0000c346f8b8 (&nft_net->commit_mutex){+.+.}-{3:3}, at: nf_tables_valid_genid+0x3c/0xd4 net/netfilter/nf_tables_api.c:10624
> 1 lock held by syz-executor.1/11588:
> 1 lock held by syz-executor.2/11593:
>  #0: ffff0001485282b8 (&nft_net->commit_mutex){+.+.}-{3:3}, at: nf_tables_valid_genid+0x3c/0xd4 net/netfilter/nf_tables_api.c:10624
> 1 lock held by syz-executor.4/11594:
>  #0: ffff0000d343fcb8 (&nft_net->commit_mutex){+.+.}-{3:3}, at: nf_tables_valid_genid+0x3c/0xd4 net/netfilter/nf_tables_api.c:10624
> 4 locks held by syz-executor.0/11595:
>  #0: ffff0001b400ef58 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested kernel/sched/core.c:559 [inline]
>  #0: ffff0001b400ef58 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock kernel/sched/sched.h:1385 [inline]
>  #0: ffff0001b400ef58 (&rq->__lock){-.-.}-{2:2}, at: rq_lock kernel/sched/sched.h:1699 [inline]
>  #0: ffff0001b400ef58 (&rq->__lock){-.-.}-{2:2}, at: __schedule+0x2e0/0x24b4 kernel/sched/core.c:6643
>  #1: ffff0001b3ffac88 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_switch+0x3c0/0x618 kernel/sched/psi.c:988
>  #2: ffff0001b401cc88 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_change+0x100/0x234 kernel/sched/psi.c:912
>  #3: ffff0001b401cc88 (&per_cpu_ptr(group->pcpu, cpu)->seq){-.-.}-{0:0}, at: psi_task_change+0x100/0x234 kernel/sched/psi.c:912
>
> =============================================
>
>
>
> ---
> This report is generated by a bot. It may contain errors.
> See https://goo.gl/tpsmEJ for more information about syzbot.
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>
> syzbot will keep track of this issue. See:
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>
> If the report is already addressed, let syzbot know by replying with:
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>
> If the report is a duplicate of another one, reply with:
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>
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This is difficult to handle as there is no reproducer and lack of
information, but one of the fixes merged in 6.8-rc4 is related to this
task hang, so I would like to see if it can be reproduced in 6.8-rc4
or later.

Ryusuke Konishi

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