syzbot


INFO: task hung in do_con_write (3)

Status: auto-obsoleted due to no activity on 2022/11/25 16:33
Subsystems: serial
[Documentation on labels]
First crash: 578d, last: 578d
Similar bugs (5)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in do_con_write serial 4 1358d 1526d 0/26 auto-closed as invalid on 2020/10/06 18:58
linux-4.14 INFO: task hung in do_con_write 9 1338d 1555d 0/1 auto-closed as invalid on 2020/11/25 15:01
upstream INFO: task hung in do_con_write (2) serial 2 914d 924d 0/26 auto-closed as invalid on 2021/12/25 05:43
upstream INFO: task hung in do_con_write (4) serial 1 114d 111d 0/26 auto-obsoleted due to no activity on 2024/03/04 00:42
linux-4.19 INFO: task hung in do_con_write 3 1339d 1396d 0/1 auto-closed as invalid on 2020/11/25 06:45

Sample crash report:
INFO: task syz-executor.4:8130 blocked for more than 143 seconds.
      Not tainted 6.0.0-rc2-syzkaller-00248-ge022620b5d05 #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.4  state:D stack:28368 pid: 8130 ppid:  3646 flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5182 [inline]
 __schedule+0xadf/0x52b0 kernel/sched/core.c:6494
 schedule+0xda/0x1b0 kernel/sched/core.c:6570
 schedule_timeout+0x1db/0x2a0 kernel/time/timer.c:1911
 ___down_common kernel/locking/semaphore.c:225 [inline]
 __down_common+0x341/0x780 kernel/locking/semaphore.c:246
 down+0x70/0x90 kernel/locking/semaphore.c:63
 console_lock+0x28/0x80 kernel/printk/printk.c:2568
 do_con_write+0x10f/0x1e40 drivers/tty/vt/vt.c:2908
 con_write+0x21/0x40 drivers/tty/vt/vt.c:3295
 process_output_block drivers/tty/n_tty.c:586 [inline]
 n_tty_write+0x4ca/0xfd0 drivers/tty/n_tty.c:2350
 do_tty_write drivers/tty/tty_io.c:1024 [inline]
 file_tty_write.constprop.0+0x499/0x8f0 drivers/tty/tty_io.c:1095
 call_write_iter include/linux/fs.h:2187 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x9e9/0xdd0 fs/read_write.c:578
 ksys_write+0x127/0x250 fs/read_write.c:631
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7f9d55289279
RSP: 002b:00007f9d5633d168 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f9d5539c050 RCX: 00007f9d55289279
RDX: 0000000000001006 RSI: 00000000200000c0 RDI: 0000000000000003
RBP: 00007f9d552e3189 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f9d558cfb1f R14: 00007f9d5633d300 R15: 0000000000022000
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8bf88770 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x26/0xc70 kernel/rcu/tasks.h:507
1 lock held by rcu_tasks_trace/13:
 #0: ffffffff8bf88470 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x26/0xc70 kernel/rcu/tasks.h:507
1 lock held by khungtaskd/28:
 #0: ffffffff8bf892c0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6492
2 locks held by getty/3285:
 #0: ffff88814ab43098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:244
 #1: ffffc90002d262f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0xef0/0x13e0 drivers/tty/n_tty.c:2177
4 locks held by syz-executor.4/8130:
 #0: ffff88802082a098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x22/0x80 drivers/tty/tty_ldisc.c:244
 #1: ffff88802082a130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: tty_write_lock drivers/tty/tty_io.c:950 [inline]
 #1: ffff88802082a130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: do_tty_write drivers/tty/tty_io.c:973 [inline]
 #1: ffff88802082a130 (&tty->atomic_write_lock){+.+.}-{3:3}, at: file_tty_write.constprop.0+0x296/0x8f0 drivers/tty/tty_io.c:1095
 #2: ffff88802082a2e8 (&tty->termios_rwsem){++++}-{3:3}, at: n_tty_write+0x1bf/0xfd0 drivers/tty/n_tty.c:2333
 #3: ffffc900030bb380 (&ldata->output_lock){+.+.}-{3:3}, at: process_output_block drivers/tty/n_tty.c:541 [inline]
 #3: ffffc900030bb380 (&ldata->output_lock){+.+.}-{3:3}, at: n_tty_write+0x5f6/0xfd0 drivers/tty/n_tty.c:2350
3 locks held by syz-executor.1/8128:
1 lock held by syz-executor.4/8219:
 #0: ffffffff8ca0b068 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2050 [inline]
 #0: ffffffff8ca0b068 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x593/0xff0 drivers/tty/tty_io.c:2133
1 lock held by syz-executor.4/8266:
 #0: ffffffff8ca0b068 (tty_mutex){+.+.}-{3:3}, at: tty_open_by_driver drivers/tty/tty_io.c:2050 [inline]
 #0: ffffffff8ca0b068 (tty_mutex){+.+.}-{3:3}, at: tty_open+0x593/0xff0 drivers/tty/tty_io.c:2133

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

NMI backtrace for cpu 1
CPU: 1 PID: 28 Comm: khungtaskd Not tainted 6.0.0-rc2-syzkaller-00248-ge022620b5d05 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/22/2022
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106
 nmi_cpu_backtrace.cold+0x46/0x14f lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x206/0x250 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+0xc18/0xf50 kernel/hung_task.c:369
 kthread+0x2e4/0x3a0 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:306
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
NMI backtrace for cpu 0 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
NMI backtrace for cpu 0 skipped: idling at acpi_safe_halt+0x6f/0xb0 drivers/acpi/processor_idle.c:112

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2022/08/27 16:30 upstream e022620b5d05 07177916 .config console log report info ci-upstream-kasan-gce INFO: task hung in do_con_write
* Struck through repros no longer work on HEAD.