syzbot


INFO: task hung in wb_shutdown (2)

Status: fixed on 2018/05/17 10:02
Reported-by: syzbot+c0cf869505e03bdf1a24@syzkaller.appspotmail.com
Fix commit: 8236b0ae31c8 bdi: wake up concurrent wb_shutdown() callers.
First crash: 1643d, last: 1604d
similar bugs (1):
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in wb_shutdown 14 1643d 1645d 0/24 closed as invalid on 2018/03/27 11:14

Sample crash report:
INFO: task kworker/0:2:1979 blocked for more than 120 seconds.
      Not tainted 4.17.0-rc2+ #24
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/0:2     D19800  1979      2 0x80000000
Workqueue: events cgwb_release_workfn
Call Trace:
 context_switch kernel/sched/core.c:2848 [inline]
 __schedule+0x801/0x1e30 kernel/sched/core.c:3490
 schedule+0xef/0x430 kernel/sched/core.c:3549
 bit_wait+0x18/0x90 kernel/sched/wait_bit.c:197
 __wait_on_bit+0xb3/0x130 kernel/sched/wait_bit.c:48
 out_of_line_wait_on_bit+0x204/0x3a0 kernel/sched/wait_bit.c:63
 wait_on_bit include/linux/wait_bit.h:76 [inline]
 wb_shutdown+0x370/0x470 mm/backing-dev.c:366
 cgwb_release_workfn+0x87/0x750 mm/backing-dev.c:509
 process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
 worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
 kthread+0x345/0x410 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412

Showing all locks held in the system:
2 locks held by kworker/u4:2/29:
 #0: 00000000ff50c69d ((wq_completion)"events_unbound"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline]
 #0: 00000000ff50c69d ((wq_completion)"events_unbound"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: 00000000ff50c69d ((wq_completion)"events_unbound"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
 #0: 00000000ff50c69d ((wq_completion)"events_unbound"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
 #0: 00000000ff50c69d ((wq_completion)"events_unbound"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
 #0: 00000000ff50c69d ((wq_completion)"events_unbound"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0: 00000000ff50c69d ((wq_completion)"events_unbound"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
 #1: 00000000c57fea68 ((work_completion)(&sub_info->work)){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
2 locks held by khungtaskd/892:
 #0: 00000000f3191291 (rcu_read_lock){....}, at: check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
 #0: 00000000f3191291 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60 kernel/hung_task.c:249
 #1: 00000000b5f4a652 (tasklist_lock){.+.+}, at: debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470
2 locks held by kworker/0:2/1979:
 #0: 0000000067d9af8b ((wq_completion)"events"){+.+.}, at: __write_once_size include/linux/compiler.h:215 [inline]
 #0: 0000000067d9af8b ((wq_completion)"events"){+.+.}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
 #0: 0000000067d9af8b ((wq_completion)"events"){+.+.}, at: atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
 #0: 0000000067d9af8b ((wq_completion)"events"){+.+.}, at: atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
 #0: 0000000067d9af8b ((wq_completion)"events"){+.+.}, at: set_work_data kernel/workqueue.c:617 [inline]
 #0: 0000000067d9af8b ((wq_completion)"events"){+.+.}, at: set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0: 0000000067d9af8b ((wq_completion)"events"){+.+.}, at: process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
 #1: 00000000a4607626 ((work_completion)(&wb->release_work)){+.+.}, at: process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
2 locks held by getty/4463:
 #0: 00000000a1d45b98 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
 #1: 00000000da655b8c (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4464:
 #0: 00000000913f5485 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
 #1: 00000000c9c0da09 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4465:
 #0: 00000000f2d2ba72 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
 #1: 00000000395b83c8 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4466:
 #0: 0000000066555597 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
 #1: 00000000c4a84ec3 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4467:
 #0: 00000000b9152073 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
 #1: 000000008ac29ae3 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4468:
 #0: 0000000043fffd7f (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
 #1: 00000000830701e4 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4469:
 #0: 00000000cf701e19 (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
 #1: 00000000e5618399 (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
1 lock held by syz-executor2/4537:
 #0: 00000000b5f4a652 (tasklist_lock){.+.+}, at: release_task.part.15+0x2b8/0x1b90 kernel/exit.c:197

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

NMI backtrace for cpu 1
CPU: 1 PID: 892 Comm: khungtaskd Not tainted 4.17.0-rc2+ #24
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1b9/0x294 lib/dump_stack.c:113
TCP: request_sock_TCPv6: Possible SYN flooding on port 20000. Sending cookies.  Check SNMP counters.
 nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
 nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
 trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
 check_hung_task kernel/hung_task.c:132 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
 watchdog+0xc10/0xf60 kernel/hung_task.c:249
 kthread+0x345/0x410 kernel/kthread.c:238
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:412
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 25208 Comm: syz-executor3 Not tainted 4.17.0-rc2+ #24
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:get_current arch/x86/include/asm/current.h:15 [inline]
RIP: 0010:debug_lockdep_rcu_enabled.part.1+0x18/0x60 kernel/rcu/update.c:301
RSP: 0018:ffff8801b54c7778 EFLAGS: 00000002
RAX: dffffc0000000000 RBX: ffff8801cfdfe200 RCX: 0000000000000000
RDX: 0000000000000004 RSI: dffffc0000000000 RDI: ffffffff8909cc20
RBP: ffff8801b54c7780 R08: ffffffff8a7158c8 R09: ffff8801b54c7628
R10: ffff8801cfdfea60 R11: ffff8801cfdfe200 R12: ffff8801b54c78a8
R13: ffffffff8a7158c8 R14: dffffc0000000000 R15: ffff8801bcb29da8
FS:  00000000027a1940(0000) GS:ffff8801dae00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000625208 CR3: 00000001ae14c000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 debug_lockdep_rcu_enabled+0x77/0x90 kernel/rcu/update.c:300
 trace_lock_release include/trace/events/lock.h:58 [inline]
 lock_release+0x6f2/0xa10 kernel/locking/lockdep.c:3938
 seqcount_lockdep_reader_access include/linux/seqlock.h:82 [inline]
 read_seqcount_begin include/linux/seqlock.h:164 [inline]
 ktime_get+0x15b/0x430 kernel/time/timekeeping.c:763
 __hrtimer_start_range_ns kernel/time/hrtimer.c:1080 [inline]
 hrtimer_start_range_ns+0x1d9/0xd10 kernel/time/hrtimer.c:1115
 hrtimer_start_expires include/linux/hrtimer.h:412 [inline]
 do_nanosleep+0x1ad/0x730 kernel/time/hrtimer.c:1686
 hrtimer_nanosleep+0x2cc/0x610 kernel/time/hrtimer.c:1743
 __do_sys_nanosleep kernel/time/hrtimer.c:1775 [inline]
 __se_sys_nanosleep kernel/time/hrtimer.c:1762 [inline]
 __x64_sys_nanosleep+0x1df/0x270 kernel/time/hrtimer.c:1762
 do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4810a1
RSP: 002b:0000000000a3e950 EFLAGS: 00000293 ORIG_RAX: 0000000000000023
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00000000004810a1
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000a3e960
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000a3e940 R11: 0000000000000293 R12: 0000000000000000
R13: 0000000000000002 R14: 000000000072bea0 R15: 000000000005a91b
Code: 00 e9 9c fd ff ff 0f 1f 00 66 2e 0f 1f 84 00 00 00 00 00 48 b8 00 00 00 00 00 fc ff df 55 48 89 e5 53 65 48 8b 1c 25 c0 ed 01 00 <48> 8d bb 34 08 00 00 48 89 fa 48 c1 ea 03 0f b6 14 02 48 89 f8 

Crashes (5064):
Manager Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Title
ci-upstream-kasan-gce 2018/04/29 21:37 upstream c61a56ababa4 bb79c6ab .config log report
ci-upstream-kasan-gce 2018/04/27 21:38 upstream d8a332730e75 7785e404 .config log report
ci-upstream-kasan-gce 2018/04/27 02:07 upstream 0644f186fc9d 73417389 .config log report
ci-upstream-kasan-gce 2018/04/26 20:21 upstream 69bfd470f462 73417389 .config log report
ci-upstream-kasan-gce 2018/04/26 18:26 upstream 69bfd470f462 73417389 .config log report
ci-upstream-kasan-gce 2018/04/26 11:07 upstream 26ed24e429d8 73417389 .config log report
ci-upstream-kasan-gce-root 2018/04/26 09:53 upstream 26ed24e429d8 73417389 .config log report
ci-upstream-kasan-gce-root 2018/04/26 06:31 upstream 26ed24e429d8 73417389 .config log report
ci-upstream-kasan-gce 2018/04/26 03:31 upstream 26ed24e429d8 73417389 .config log report
ci-upstream-kasan-gce 2018/04/25 22:30 upstream 3be4aaf4e2d3 73417389 .config log report
ci-upstream-kasan-gce 2018/04/25 19:28 upstream 3be4aaf4e2d3 73417389 .config log report
ci-upstream-kasan-gce 2018/04/25 15:01 upstream 3be4aaf4e2d3 73417389 .config log report
ci-upstream-kasan-gce-root 2018/04/25 12:45 upstream 3be4aaf4e2d3 73417389 .config log report
ci-upstream-kasan-gce 2018/04/25 05:07 upstream 24cac7009cb1 37e76fe2 .config log report
ci-upstream-kasan-gce-root 2018/04/24 23:31 upstream 24cac7009cb1 37e76fe2 .config log report
ci-upstream-kasan-gce-root 2018/04/24 09:02 upstream 6d08b06e67cd e7e85d36 .config log report
ci-upstream-kasan-gce 2018/04/24 05:17 upstream 6d08b06e67cd e7e85d36 .config log report
ci-upstream-kasan-gce 2018/04/23 08:30 upstream 5ec83b22a2dd d23fcf6c .config log report
ci-upstream-kasan-gce 2018/04/22 19:28 upstream 285848b0f407 d23fcf6c .config log report
ci-upstream-kasan-gce 2018/04/22 17:17 upstream 285848b0f407 d23fcf6c .config log report
ci-upstream-kasan-gce 2018/04/22 13:35 upstream 285848b0f407 d23fcf6c .config log report
ci-upstream-kasan-gce 2018/04/21 23:19 upstream 5e7c7806111a d23fcf6c .config log report
ci-upstream-kasan-gce 2018/04/21 10:37 upstream 83beed7b2b26 ca03d688 .config log report
ci-upstream-kasan-gce 2018/04/21 02:11 upstream 83beed7b2b26 ca03d688 .config log report
ci-upstream-kasan-gce 2018/04/20 10:51 upstream 87ef12027b9b eae05cb0 .config log report
ci-upstream-kasan-gce-root 2018/04/20 06:55 upstream 87ef12027b9b eae05cb0 .config log report
ci-upstream-kasan-gce-root 2018/04/20 04:46 upstream 87ef12027b9b eae05cb0 .config log report
ci-upstream-kasan-gce 2018/04/19 14:04 upstream 87ef12027b9b 3642839c .config log report
ci-upstream-kasan-gce-root 2018/04/16 23:23 upstream a27fc14219f2 b80fd3b5 .config log report
ci-upstream-kasan-gce 2018/04/14 04:08 upstream 1bad9ce155a7 7a67784c .config log report
ci-upstream-kasan-gce-root 2018/04/14 01:18 upstream 1bad9ce155a7 7a67784c .config log report
ci-upstream-kasan-gce-root 2018/04/13 21:34 upstream 1bad9ce155a7 7a67784c .config log report
ci-upstream-kasan-gce 2018/04/13 19:11 upstream 16e205cf42da 0a0c5db6 .config log report
ci-upstream-kasan-gce 2018/04/12 18:41 upstream c17b0aadb7d8 eb2295de .config log report
ci-upstream-kasan-gce 2018/04/11 22:21 upstream b284d4d5a678 9cd56d71 .config log report
ci-upstream-kasan-gce-root 2018/04/11 21:02 upstream b284d4d5a678 9cd56d71 .config log report
ci-upstream-kasan-gce-root 2018/04/09 09:00 upstream 3fd14cdcc05a f13fb445 .config log report
ci-upstream-kasan-gce-root 2018/04/08 13:39 upstream 3fd14cdcc05a 77bd5117 .config log report
ci-upstream-kasan-gce-root 2018/04/07 13:03 upstream 3fd14cdcc05a 66f22a7f .config log report
ci-upstream-kasan-gce 2018/04/06 11:01 upstream 38c23685b273 4f1152d4 .config log report
ci-upstream-kasan-gce-root 2018/04/06 01:07 upstream 3c8ba0d61d04 a932eae6 .config log report
ci-upstream-kasan-gce 2018/04/05 21:34 upstream e02d37bf55a9 a932eae6 .config log report
ci-upstream-kasan-gce 2018/04/05 16:03 upstream 3e968c9f1401 5e1ccffc .config log report
ci-upstream-kasan-gce 2018/03/28 07:38 upstream 3eb2ce825ea1 bf5e585c .config log report
ci-upstream-kasan-gce-386 2018/04/11 08:55 upstream f2d285669aae 8b8de427 .config log report
ci-upstream-kasan-gce-386 2018/04/10 19:20 upstream f2d285669aae 8b8de427 .config log report
ci-upstream-kasan-gce-386 2018/04/06 04:25 upstream f2d285669aae a932eae6 .config log report
ci-upstream-kasan-gce-386 2018/04/05 23:55 upstream f2d285669aae a932eae6 .config log report
* Struck through repros no longer work on HEAD.