INFO: task hung in n_tty_flush_buffer (2)

Status: auto-obsoleted due to no activity on 2025/02/04 04:28
Subsystems: serial
[Documentation on labels]
First crash: 631d, last: 631d
▶ ▼ Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
android-49 INFO: task hung in n_tty_flush_buffer 1 syz, C 6 2950d 2664d 0/3 public: reported C repro on 2019/04/14 00:00
upstream INFO: task hung in n_tty_flush_buffer (3) serial prio:high 1 1 139d 139d 0/29 auto-obsoleted due to no activity on 2026/06/11 06:05
upstream INFO: task hung in n_tty_flush_buffer serial 1 6 2951d 3025d 8/29 fixed on 2018/07/09 18:05
linux-4.14 INFO: task hung in n_tty_flush_buffer 1 1 2275d 2275d 0/1 auto-closed as invalid on 2020/09/03 14:06

Sample crash report:
INFO: task kworker/1:1:46 blocked for more than 143 seconds.
      Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:1     state:D stack:21120 pid:46    tgid:46    ppid:2      flags:0x00004000
Workqueue: events vc_SAK
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0xe55/0x5740 kernel/sched/core.c:6690
 __schedule_loop kernel/sched/core.c:6767 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6782
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6839
 rwsem_down_write_slowpath+0x539/0x12a0 kernel/locking/rwsem.c:1176
 __down_write_common kernel/locking/rwsem.c:1304 [inline]
 __down_write kernel/locking/rwsem.c:1313 [inline]
 down_write+0x1d8/0x200 kernel/locking/rwsem.c:1578
 n_tty_flush_buffer+0x25/0x1b0 drivers/tty/n_tty.c:358
 tty_buffer_flush+0x236/0x310 drivers/tty/tty_buffer.c:241
 tty_ldisc_flush+0x64/0xe0 drivers/tty/tty_ldisc.c:388
 __do_SAK+0x6a1/0x800 drivers/tty/tty_io.c:3038
 vc_SAK+0x7f/0x310 drivers/tty/vt/vt_ioctl.c:993
 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
INFO: task kworker/u8:3:53 blocked for more than 143 seconds.
      Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:3    state:D stack:23328 pid:53    tgid:53    ppid:2      flags:0x00004000
Workqueue: events_unbound flush_to_ldisc
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0xe55/0x5740 kernel/sched/core.c:6690
 __schedule_loop kernel/sched/core.c:6767 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6782
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6839
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x5b8/0x9c0 kernel/locking/mutex.c:752
 flush_to_ldisc+0x31/0x780 drivers/tty/tty_buffer.c:467
 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
INFO: task kworker/1:3:13423 blocked for more than 143 seconds.
      Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:3     state:D stack:23344 pid:13423 tgid:13423 ppid:2      flags:0x00004000
Workqueue: events console_callback
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0xe55/0x5740 kernel/sched/core.c:6690
 __schedule_loop kernel/sched/core.c:6767 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6782
 schedule_timeout+0x258/0x2a0 kernel/time/timer.c:2591
 ___down_common+0x2d7/0x460 kernel/locking/semaphore.c:225
 __down_common kernel/locking/semaphore.c:246 [inline]
 __down+0x20/0x30 kernel/locking/semaphore.c:254
 down+0x74/0xa0 kernel/locking/semaphore.c:63
 console_lock+0x5b/0xa0 kernel/printk/printk.c:2808
 console_callback+0x63/0x4c0 drivers/tty/vt/vt.c:3120
 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
INFO: task syz.3.1900:14485 blocked for more than 143 seconds.
      Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.1900      state:D stack:27312 pid:14485 tgid:14481 ppid:5831   flags:0x00004006
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0xe55/0x5740 kernel/sched/core.c:6690
 __schedule_loop kernel/sched/core.c:6767 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6782
 schedule_timeout+0x258/0x2a0 kernel/time/timer.c:2591
 ___down_common+0x2d7/0x460 kernel/locking/semaphore.c:225
 __down_common kernel/locking/semaphore.c:246 [inline]
 __down+0x20/0x30 kernel/locking/semaphore.c:254
 down+0x74/0xa0 kernel/locking/semaphore.c:63
 console_lock+0x5b/0xa0 kernel/printk/printk.c:2808
 do_con_write+0x154/0x7bb0 drivers/tty/vt/vt.c:3056
 con_put_char+0x74/0xa0 drivers/tty/vt/vt.c:3442
 tty_put_char+0xbc/0x160 drivers/tty/tty_io.c:3167
 do_output_char+0x151/0x840 drivers/tty/n_tty.c:469
 process_output drivers/tty/n_tty.c:494 [inline]
 n_tty_write+0x4c3/0x1140 drivers/tty/n_tty.c:2400
 iterate_tty_write drivers/tty/tty_io.c:1015 [inline]
 file_tty_write.constprop.0+0x506/0x9a0 drivers/tty/tty_io.c:1090
 new_sync_write fs/read_write.c:590 [inline]
 vfs_write+0x5ae/0x1150 fs/read_write.c:683
 ksys_write+0x12f/0x260 fs/read_write.c:736
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fa805f7e719
RSP: 002b:00007fa806cdc038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fa806136130 RCX: 00007fa805f7e719
RDX: 0000000000001006 RSI: 0000000020001040 RDI: 000000000000000c
RBP: 00007fa805ff139e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fa806136130 R15: 00007fff1674b078
 </TASK>
INFO: task syz.1.1923:14561 blocked for more than 143 seconds.
      Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.1923      state:D stack:27008 pid:14561 tgid:14560 ppid:5828   flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0xe55/0x5740 kernel/sched/core.c:6690
 __schedule_loop kernel/sched/core.c:6767 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6782
 schedule_timeout+0x258/0x2a0 kernel/time/timer.c:2591
 ___down_common+0x2d7/0x460 kernel/locking/semaphore.c:225
 __down_common kernel/locking/semaphore.c:246 [inline]
 __down+0x20/0x30 kernel/locking/semaphore.c:254
 down+0x74/0xa0 kernel/locking/semaphore.c:63
 console_lock+0x5b/0xa0 kernel/printk/printk.c:2808
 con_install+0x9a/0x600 drivers/tty/vt/vt.c:3517
 tty_driver_install_tty drivers/tty/tty_io.c:1304 [inline]
 tty_init_dev.part.0+0x99/0x660 drivers/tty/tty_io.c:1416
 tty_init_dev include/linux/err.h:67 [inline]
 tty_open_by_driver drivers/tty/tty_io.c:2082 [inline]
 tty_open+0xac1/0xf80 drivers/tty/tty_io.c:2129
 chrdev_open+0x237/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x6ca/0x1530 fs/open.c:958
 vfs_open+0x82/0x3f0 fs/open.c:1088
 do_open fs/namei.c:3774 [inline]
 path_openat+0x1e6a/0x2d60 fs/namei.c:3933
 do_filp_open+0x1dc/0x430 fs/namei.c:3960
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1415
 do_sys_open fs/open.c:1430 [inline]
 __do_sys_openat fs/open.c:1446 [inline]
 __se_sys_openat fs/open.c:1441 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1441
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f396c97d0b0
RSP: 002b:00007f396d821b70 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f396c97d0b0
RDX: 0000000000000002 RSI: 00007f396d821c10 RDI: 00000000ffffff9c
RBP: 00007f396d821c10 R08: 0000000000000000 R09: 00007f396d821986
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f396cb35f80 R15: 00007ffd45b32ea8
 </TASK>
INFO: task syz.1.1923:14562 blocked for more than 143 seconds.
      Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.1923      state:D stack:27600 pid:14562 tgid:14560 ppid:5828   flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0xe55/0x5740 kernel/sched/core.c:6690
 __schedule_loop kernel/sched/core.c:6767 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6782
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6839
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x5b8/0x9c0 kernel/locking/mutex.c:752
 tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 tty_open+0x53d/0xf80 drivers/tty/tty_io.c:2129
 chrdev_open+0x237/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x6ca/0x1530 fs/open.c:958
 vfs_open+0x82/0x3f0 fs/open.c:1088
 do_open fs/namei.c:3774 [inline]
 path_openat+0x1e6a/0x2d60 fs/namei.c:3933
 do_filp_open+0x1dc/0x430 fs/namei.c:3960
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1415
 do_sys_open fs/open.c:1430 [inline]
 __do_sys_openat fs/open.c:1446 [inline]
 __se_sys_openat fs/open.c:1441 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1441
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f396c97d0b0
RSP: 002b:00007f396d800b70 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f396c97d0b0
RDX: 0000000000000002 RSI: 00007f396d800c10 RDI: 00000000ffffff9c
RBP: 00007f396d800c10 R08: 0000000000000000 R09: 00007f396d800986
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f396cb36058 R15: 00007ffd45b32ea8
 </TASK>
INFO: task syz.0.1938:14610 blocked for more than 143 seconds.
      Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.1938      state:D stack:26808 pid:14610 tgid:14609 ppid:5841   flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5328 [inline]
 __schedule+0xe55/0x5740 kernel/sched/core.c:6690
 __schedule_loop kernel/sched/core.c:6767 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6782
 schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6839
 __mutex_lock_common kernel/locking/mutex.c:684 [inline]
 __mutex_lock+0x5b8/0x9c0 kernel/locking/mutex.c:752
 tty_open_by_driver drivers/tty/tty_io.c:2046 [inline]
 tty_open+0x53d/0xf80 drivers/tty/tty_io.c:2129
 chrdev_open+0x237/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x6ca/0x1530 fs/open.c:958
 vfs_open+0x82/0x3f0 fs/open.c:1088
 do_open fs/namei.c:3774 [inline]
 path_openat+0x1e6a/0x2d60 fs/namei.c:3933
 do_filp_open+0x1dc/0x430 fs/namei.c:3960
 do_sys_openat2+0x17a/0x1e0 fs/open.c:1415
 do_sys_open fs/open.c:1430 [inline]
 __do_sys_openat fs/open.c:1446 [inline]
 __se_sys_openat fs/open.c:1441 [inline]
 __x64_sys_openat+0x175/0x210 fs/open.c:1441
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f820157d0b0
RSP: 002b:00007f82023afb70 EFLAGS: 00000293 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 00007f820157d0b0
RDX: 0000000000000002 RSI: 00007f82023afc10 RDI: 00000000ffffff9c
RBP: 00007f82023afc10 R08: 0000000000000000 R09: 00007f82023af986
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8201735f80 R15: 00007ffcb5de3f28
 </TASK>
INFO: lockdep is turned off.
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 30 Comm: khungtaskd Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
 watchdog+0xf0c/0x1240 kernel/hung_task.c:379
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 17441 Comm: syz.0.2351 Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:folio_mark_dirty+0xa/0x150 mm/page-writeback.c:2892
Code: cc cc 48 89 df e8 86 13 2a 00 eb 93 0f 1f 40 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 41 54 49 89 fc 55 <53> e8 50 89 c8 ff 4c 89 e7 e8 18 ea 08 00 48 85 c0 0f 84 e9 00 00
RSP: 0018:ffffc9000302fb68 EFLAGS: 00000246
RAX: 0000000000040000 RBX: ffffea000158e9c0 RCX: ffffc900434d5000
RDX: 0000000000040000 RSI: ffffffff81ccc496 RDI: ffffea000158e9c0
RBP: ffffea000158e9f4 R08: 0000000000000001 R09: fffff940002b1d38
R10: ffffea000158e9c7 R11: 0000000000000000 R12: ffffea000158e9c0
R13: ffff88807c5cc2d0 R14: 0000000000001000 R15: ffff88807c5cc320
FS:  00007f4fdbf7a6c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4fdbf59d58 CR3: 00000000b3746000 CR4: 00000000003526f0
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 shmem_write_end+0x1f2/0x4d0 mm/shmem.c:3076
 generic_perform_write+0x4e5/0x920 mm/filemap.c:4069
 shmem_file_write_iter+0x10e/0x140 mm/shmem.c:3218
 new_sync_write fs/read_write.c:590 [inline]
 vfs_write+0x5ae/0x1150 fs/read_write.c:683
 ksys_write+0x12f/0x260 fs/read_write.c:736
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f4fdb17e719
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f4fdbf7a038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f4fdb336130 RCX: 00007f4fdb17e719
RDX: 000000000208e24b RSI: 0000000020000000 RDI: 0000000000000006
RBP: 00007f4fdb1f139e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f4fdb336130 R15: 00007ffc363979c8
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/11/06 04:27 upstream 2e1b3cc9d7f7 3a465482 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root INFO: task hung in n_tty_flush_buffer
* Struck through repros no longer work on HEAD.