syzbot


INFO: task hung in nilfs_segctor_thread (4)

Status: upstream: reported C repro on 2026/03/30 01:14
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+ca3bc754a90607840f57@syzkaller.appspotmail.com
First crash: 109d, last: 4d08h
Fix bisection: failed (error log, bisect log)
  
Bug presence (1)
Date Name Commit Repro Result
2026/03/30 upstream (ToT) 7aaa8047eafd C [report] INFO: task hung in nilfs_segctor_thread
Similar bugs (15)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in nilfs_segctor_thread (5) nilfs 1 1 383d 383d 0/29 auto-obsoleted due to no activity on 2025/09/27 08:54
linux-6.6 INFO: task hung in nilfs_segctor_thread 1 1 18d 18d 0/2 upstream: reported on 2026/06/28 21:10
linux-4.19 INFO: task hung in nilfs_segctor_thread nilfs2 1 C 41 1249d 1350d 0/1 upstream: reported C repro on 2022/11/05 03:06
upstream INFO: task hung in nilfs_segctor_thread (6) nilfs 1 C done 41 72d 212d 29/29 fixed on 2026/05/06 16:40
linux-5.15 INFO: task hung in nilfs_segctor_thread (2) 1 2 716d 796d 0/3 auto-obsoleted due to no activity on 2024/11/07 22:53
upstream INFO: task hung in nilfs_segctor_thread (3) nilfs 1 138 702d 727d 0/29 auto-obsoleted due to no activity on 2024/10/22 18:08
upstream INFO: task hung in nilfs_segctor_thread nilfs 1 C error 94 1171d 1345d 22/29 fixed on 2023/06/08 14:41
linux-5.15 INFO: task hung in nilfs_segctor_thread 1 3 1182d 1194d 0/3 auto-obsoleted due to no activity on 2023/08/20 05:29
upstream INFO: task hung in nilfs_segctor_thread (7) prio:high nilfs 1 syz error 18 31d 30d 0/29 closed as dup on 2026/06/19 02:51
upstream INFO: task hung in nilfs_segctor_thread (4) nilfs 1 1 622d 622d 0/29 auto-obsoleted due to no activity on 2025/01/31 15:40
linux-4.14 INFO: task hung in nilfs_segctor_thread nilfs2 1 C 1 1247d 1247d 0/1 upstream: reported C repro on 2023/02/16 07:03
linux-6.1 INFO: task hung in nilfs_segctor_thread (2) 1 2 109d 192d 0/3 auto-obsoleted due to no activity on 2026/07/07 21:46
upstream INFO: task hung in nilfs_segctor_thread (2) nilfs 1 C inconclusive 98 769d 879d 26/29 fixed on 2024/07/09 19:14
linux-6.1 INFO: task hung in nilfs_segctor_thread 1 40 651d 796d 0/3 auto-obsoleted due to no activity on 2024/12/12 18:46
linux-5.15 INFO: task hung in nilfs_segctor_thread (3) 1 1 590d 590d 0/3 auto-obsoleted due to no activity on 2025/03/13 18:17
Last patch testing requests (1)
Created Duration User Patch Repo Result
2026/04/13 04:25 20m retest repro linux-5.15.y report log

Sample crash report:
INFO: task segctord:4399 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:segctord        state:D
 stack:29104 pid: 4399 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 rwsem_down_write_slowpath+0xe63/0x13a0 kernel/locking/rwsem.c:1165
 nilfs_transaction_lock+0x24a/0x4b0 fs/nilfs2/segment.c:357
 nilfs_segctor_thread_construct fs/nilfs2/segment.c:2562 [inline]
 nilfs_segctor_thread+0x528/0x1100 fs/nilfs2/segment.c:2647
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
INFO: task segctord:4424 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:segctord        state:D
 stack:29104 pid: 4424 ppid:     2 flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5049 [inline]
 __schedule+0x11c3/0x4350 kernel/sched/core.c:6395
 schedule+0x11b/0x1e0 kernel/sched/core.c:6478
 rwsem_down_write_slowpath+0xe63/0x13a0 kernel/locking/rwsem.c:1165
 nilfs_transaction_lock+0x24a/0x4b0 fs/nilfs2/segment.c:357
 nilfs_segctor_thread_construct fs/nilfs2/segment.c:2562 [inline]
 nilfs_segctor_thread+0x528/0x1100 fs/nilfs2/segment.c:2647
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
 #0: ffffffff8c31ef20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3944:
 #0: ffff88802cae9098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: 
ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x594/0x1a50 drivers/tty/n_tty.c:2158
3 locks held by syz.2.19/4356:
2 locks held by syz.1.18/4389:
3 locks held by syz.0.17/4393:
 #0: ffff88802b4de460 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5c/0x200 fs/namespace.c:430
 #1: ffff88807ba782a0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_lock+0x24a/0x4b0 fs/nilfs2/segment.c:357
 #2: ffff8880b903a358 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x25/0x130 kernel/sched/core.c:475
3 locks held by syz.4.21/4401:
3 locks held by syz.3.20/4397:
1 lock held by segctord/4399:
 #0: ffff88802c1e32a0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_lock+0x24a/0x4b0 fs/nilfs2/segment.c:357
2 locks held by syz.5.22/4425:
1 lock held by segctord/4424:
 #0: ffff8880208782a0 (&nilfs->ns_segctor_sem){++++}-{3:3}
, at: nilfs_transaction_lock+0x24a/0x4b0 fs/nilfs2/segment.c:357
2 locks held by syz.6.23/4510:
1 lock held by segctord/4508:
 #0: ffff888075c332a0 (
&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_lock+0x24a/0x4b0 fs/nilfs2/segment.c:357
2 locks held by syz.7.24/4528:
6 locks held by syz.8.25/4526:
1 lock held by segctord/4527:
 #0: ffff888019fef2a0 (&nilfs->ns_segctor_sem){++++}-{3:3}, at: nilfs_transaction_lock+0x24a/0x4b0 fs/nilfs2/segment.c:357
2 locks held by syz.9.26/4539:
1 lock held by udevd/4886:
2 locks held by syz.4.372/5405:

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a2/0x3d0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
 watchdog+0xe1b/0xe60 kernel/hung_task.c:369
 kthread+0x42e/0x520 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 4526 Comm: syz.8.25 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:io_serial_in+0x73/0xb0 drivers/tty/serial/8250/8250_port.c:461
Code: e8 62 1c 25 fd 44 89 f9 d3 e3 49 83 c6 40 4c 89 f0 48 c1 e8 03 42 80 3c 20 00 74 08 4c 89 f7 e8 c3 3a 6a fd 41 03 1e 89 da ec <0f> b6 c0 5b 41 5c 41 5e 41 5f c3 44 89 f9 80 e1 07 38 c1 7c aa 4c
RSP: 0018:ffffc9000408eab8 EFLAGS: 00000002
RAX: 1ffffffff2cc2d00 RBX: 00000000000003fd RCX: 0000000000000000
RDX: 00000000000003fd RSI: 0000000000000000 RDI: 0000000000000020
RBP: 0000000000000020 R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff52000811d4c R12: dffffc0000000000
R13: dffffc0000000000 R14: ffffffff966168a0 R15: 0000000000000000
FS:  00007fd0fba146c0(0000) GS:ffff8880b9000000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f35070b4dac CR3: 0000000022d72000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 serial_in drivers/tty/serial/8250/8250.h:116 [inline]
 wait_for_xmitr+0xc7/0x240 drivers/tty/serial/8250/8250_port.c:2069
 serial8250_console_putchar+0x1a/0x50 drivers/tty/serial/8250/8250_port.c:3315
 uart_console_write+0xaa/0x100 drivers/tty/serial/serial_core.c:1981
 serial8250_console_write+0xb90/0xf50 drivers/tty/serial/8250/8250_port.c:3392
 call_console_drivers kernel/printk/printk.c:-1 [inline]
 console_unlock+0xb47/0x10f0 kernel/printk/printk.c:2744
 vprintk_emit+0xc0/0x150 kernel/printk/printk.c:2274
 _printk+0xda/0x130 kernel/printk/printk.c:2299
 __nilfs_msg+0x2d8/0x3b0 fs/nilfs2/super.c:78
 nilfs_sufile_updatev+0x218/0x640 fs/nilfs2/sufile.c:174
 nilfs_sufile_freev fs/nilfs2/sufile.h:87 [inline]
 nilfs_segctor_collect_blocks fs/nilfs2/segment.c:1246 [inline]
 nilfs_segctor_collect fs/nilfs2/segment.c:1534 [inline]
 nilfs_segctor_do_construct+0x1ff7/0x6c10 fs/nilfs2/segment.c:2090
 nilfs_segctor_construct+0x170/0x690 fs/nilfs2/segment.c:2455
 nilfs_clean_segments+0x3cb/0xac0 fs/nilfs2/segment.c:2529
 nilfs_ioctl_clean_segments fs/nilfs2/ioctl.c:946 [inline]
 nilfs_ioctl+0x2068/0x21b0 fs/nilfs2/ioctl.c:1310
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:874 [inline]
 __se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd0fc3b3e59
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fd0fba14028 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007fd0fc63bfa0 RCX: 00007fd0fc3b3e59
RDX: 0000200000000640 RSI: 0000000040786e88 RDI: 0000000000000005
RBP: 00007fd0fc449e6f R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd0fc63c038 R14: 00007fd0fc63bfa0 R15: 00007fff55f0ce18
 </TASK>

Crashes (9):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/07/11 21:49 linux-5.15.y c86c4726e7f0 d78ea535 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
2026/03/30 01:13 linux-5.15.y 91d48252ad4b b5ceaad2 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
2026/07/13 07:49 linux-5.15.y c86c4726e7f0 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
2026/07/11 17:32 linux-5.15.y c86c4726e7f0 d78ea535 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
2026/06/05 09:56 linux-5.15.y dc027a595035 197909be .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
2026/05/31 15:33 linux-5.15.y 241d66fa280c 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
2026/05/31 11:10 linux-5.15.y 241d66fa280c 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
2026/05/30 17:39 linux-5.15.y 241d66fa280c 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
2026/05/30 17:18 linux-5.15.y 241d66fa280c 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in nilfs_segctor_thread
* Struck through repros no longer work on HEAD.