bisecting fixing commit since 96d454cd2c1668010406ea4c28ab915bcbb747f4 building syzkaller on d5a3ae1f760e7cb2cd5a721d9645ae22eae114fe testing commit 96d454cd2c1668010406ea4c28ab915bcbb747f4 with gcc (GCC) 8.1.0 kernel signature: bf115351b70b00066b9d48f31ea766ac746ffc7314ed74c69b0afe36a2f13f13 run #0: crashed: INFO: task hung in do_proc_bulk run #1: crashed: INFO: task hung in do_proc_bulk run #2: crashed: INFO: task hung in do_proc_bulk run #3: crashed: INFO: task hung in do_proc_bulk run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK reproducer seems to be flaky testing current HEAD 52cd5f9c22eeef26d05f9d9338ba4eb38f14dd3a testing commit 52cd5f9c22eeef26d05f9d9338ba4eb38f14dd3a with gcc (GCC) 8.1.0 kernel signature: 651363f20f9a7f8b46a1a654782b61ecc78b602c9b71e002c8aeec8446b4ca93 run #0: crashed: INFO: task hung in do_proc_bulk run #1: crashed: INFO: task hung in do_proc_bulk run #2: OK run #3: OK run #4: OK run #5: OK run #6: OK run #7: OK run #8: OK run #9: OK Reproducer flagged being flaky revisions tested: 2, total time: 31m28.433054829s (build: 10m0.770834199s, test: 20m51.338801911s) the crash still happens on HEAD commit msg: Merge tag 'ntb-5.11' of git://github.com/jonmason/ntb crash: INFO: task hung in do_proc_bulk INFO: task syz-executor.0:16509 blocked for more than 143 seconds. Not tainted 5.10.0-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.0 state:D stack:14104 pid:16509 ppid: 6172 flags:0x00000004 Call Trace: context_switch kernel/sched/core.c:4313 [inline] __schedule+0x420/0x900 kernel/sched/core.c:5064 schedule+0x38/0xe0 kernel/sched/core.c:5143 schedule_timeout+0x233/0x2e0 kernel/time/timer.c:1854 do_wait_for_common kernel/sched/completion.c:85 [inline] __wait_for_common kernel/sched/completion.c:106 [inline] wait_for_common kernel/sched/completion.c:117 [inline] wait_for_completion_timeout+0xa9/0x120 kernel/sched/completion.c:157 usb_start_wait_urb+0x7d/0xf0 drivers/usb/core/message.c:63 do_proc_bulk+0x13f/0x2f0 drivers/usb/core/devio.c:1231 proc_bulk_compat drivers/usb/core/devio.c:2052 [inline] usbdev_do_ioctl drivers/usb/core/devio.c:2603 [inline] usbdev_ioctl+0x6f1/0x10f0 drivers/usb/core/devio.c:2708 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl fs/ioctl.c:739 [inline] __x64_sys_ioctl+0x7c/0xb0 fs/ioctl.c:739 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x45d5b9 RSP: 002b:00007f3c871a7c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000001aa80 RCX: 000000000045d5b9 RDX: 0000000020000000 RSI: 00000000c0185502 RDI: 0000000000000003 RBP: 000000000118cf80 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118cf4c R13: 00007ffd7550137f R14: 00007f3c871a89c0 R15: 000000000118cf4c Showing all locks held in the system: 1 lock held by khungtaskd/1175: #0: ffffffff845da740 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x15/0x17a kernel/locking/lockdep.c:6255 1 lock held by in:imklog/5787: #0: ffff88810b6ff0f0 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x45/0x50 fs/file.c:949 ============================================= NMI backtrace for cpu 0 CPU: 0 PID: 1175 Comm: khungtaskd Not tainted 5.10.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0xa3/0xc8 lib/dump_stack.c:120 nmi_cpu_backtrace.cold.8+0x53/0x6d lib/nmi_backtrace.c:105 nmi_trigger_cpumask_backtrace+0xd5/0xf0 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline] watchdog+0x57f/0x670 kernel/hung_task.c:294 kthread+0x145/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296 Sending NMI from CPU 0 to CPUs 1: NMI backtrace for cpu 1 CPU: 1 PID: 465 Comm: kworker/u4:5 Not tainted 5.10.0-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_iv_send_outstanding_bat_ogm_packet RIP: 0010:lock_release+0x18a/0x310 kernel/locking/lockdep.c:5461 Code: cc d7 dd 7e 83 fa 01 0f 85 48 01 00 00 48 83 3d 43 22 29 03 00 0f 84 58 01 00 00 48 89 ef 57 9d 0f 1f 44 00 00 48 8b 44 24 10 <65> 48 33 04 25 28 00 00 00 0f 85 70 01 00 00 48 83 c4 18 5b 5d 41 RSP: 0018:ffffc90000e33d80 EFLAGS: 00000286 RAX: 0e728c411aeade00 RBX: ffff888100c58040 RCX: ffffc90000e33d8c RDX: 0000000000000001 RSI: ffffffff83ea8574 RDI: 0000000000000286 RBP: 0000000000000286 R08: 0000000000000003 R09: 0000000000000000 R10: 0000000000000001 R11: ffff888115731098 R12: ffffffff845da740 R13: ffffffff82f8f3a3 R14: 0000000000000004 R15: 00000000000003c7 FS: 0000000000000000(0000) GS:ffff888237d00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fcd6e076018 CR3: 0000000105dad001 CR4: 00000000001706e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rcu_lock_release include/linux/rcupdate.h:258 [inline] rcu_read_unlock include/linux/rcupdate.h:696 [inline] batadv_iv_ogm_slide_own_bcast_window net/batman-adv/bat_iv_ogm.c:771 [inline] batadv_iv_ogm_schedule_buff+0x26b/0x690 net/batman-adv/bat_iv_ogm.c:825 batadv_iv_ogm_schedule net/batman-adv/bat_iv_ogm.c:869 [inline] batadv_iv_send_outstanding_bat_ogm_packet+0xad/0x1f0 net/batman-adv/bat_iv_ogm.c:1723 process_one_work+0x293/0x600 kernel/workqueue.c:2275 worker_thread+0x38/0x380 kernel/workqueue.c:2421 kthread+0x145/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296