bisecting fixing commit since fb0155a09b0224a7147cb07a4ce6034c8d29667f building syzkaller on 1b88c6d5c8477f1d4fb3b389443b200acc32e9a8 testing commit fb0155a09b0224a7147cb07a4ce6034c8d29667f with gcc (GCC) 8.1.0 kernel signature: d4eb72b5eab2125693d379506626ef1f391b4be87520d7ac9a0c8bef0e496ea1 all runs: crashed: INFO: task hung in nbd_ioctl testing current HEAD c84e1efae022071a4fcf9f1899bf71777c49943a testing commit c84e1efae022071a4fcf9f1899bf71777c49943a with gcc (GCC) 8.1.0 kernel signature: 338f224ffbcbf02efe737e15c658c4ed47d91d41168ad11acf0015c18de0bd5b all runs: crashed: INFO: task hung in nbd_ioctl revisions tested: 2, total time: 23m46.777622168s (build: 10m2.453064459s, test: 13m12.661108677s) the crash still happens on HEAD commit msg: Merge tag 'asm-generic-fixes-5.10-2' of git://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic crash: INFO: task hung in nbd_ioctl INFO: task syz-executor.2:8207 blocked for more than 143 seconds. Not tainted 5.10.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.2 state:D stack:14248 pid: 8207 ppid: 6145 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:3779 [inline] __schedule+0x418/0x900 kernel/sched/core.c:4528 schedule+0x38/0xe0 kernel/sched/core.c:4606 schedule_timeout+0x275/0x360 kernel/time/timer.c:1847 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+0xa7/0x110 kernel/sched/completion.c:138 flush_workqueue+0x1ca/0x590 kernel/workqueue.c:2835 nbd_start_device_ioctl drivers/block/nbd.c:1332 [inline] __nbd_ioctl drivers/block/nbd.c:1409 [inline] nbd_ioctl+0x268/0x3a0 drivers/block/nbd.c:1449 __blkdev_driver_ioctl block/ioctl.c:228 [inline] blkdev_ioctl+0x1d1/0x2b0 block/ioctl.c:623 block_ioctl+0x3a/0x40 fs/block_dev.c:1869 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: 0033:0x45dd99 RSP: 002b:00007f771e631c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000012e80 RCX: 000000000045dd99 RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003 RBP: 000000000118c000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bfd4 R13: 00007ffe463a127f R14: 00007f771e6329c0 R15: 000000000118bfd4 INFO: task syz-executor.0:8241 blocked for more than 143 seconds. Not tainted 5.10.0-rc5-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:syz-executor.0 state:D stack:14424 pid: 8241 ppid: 6137 flags:0x00004004 Call Trace: context_switch kernel/sched/core.c:3779 [inline] __schedule+0x418/0x900 kernel/sched/core.c:4528 schedule+0x38/0xe0 kernel/sched/core.c:4606 schedule_timeout+0x275/0x360 kernel/time/timer.c:1847 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+0xa7/0x110 kernel/sched/completion.c:138 flush_workqueue+0x1ca/0x590 kernel/workqueue.c:2835 nbd_start_device_ioctl drivers/block/nbd.c:1332 [inline] __nbd_ioctl drivers/block/nbd.c:1409 [inline] nbd_ioctl+0x268/0x3a0 drivers/block/nbd.c:1449 __blkdev_driver_ioctl block/ioctl.c:228 [inline] blkdev_ioctl+0x1d1/0x2b0 block/ioctl.c:623 block_ioctl+0x3a/0x40 fs/block_dev.c:1869 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: 0033:0x45dd99 RSP: 002b:00007f5b82394c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 0000000000012e80 RCX: 000000000045dd99 RDX: 0000000000000000 RSI: 000000000000ab03 RDI: 0000000000000003 RBP: 000000000118c000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000118bfd4 R13: 00007fff2523556f R14: 00007f5b823959c0 R15: 000000000118bfd4 Showing all locks held in the system: 1 lock held by khungtaskd/1100: #0: ffffffff847fbf40 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x15/0x17a kernel/locking/lockdep.c:6255 1 lock held by in:imklog/5785: 2 locks held by kworker/u5:3/6290: #0: ffff8881165ad138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff8881165ad138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff8881165ad138 ((wq_completion)knbd0-recv){+.+.}-{0:0}, at: process_one_work+0x1e6/0x600 kernel/workqueue.c:2243 #1: ffffc900002d3e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #1: ffffc900002d3e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #1: ffffc900002d3e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x1e6/0x600 kernel/workqueue.c:2243 2 locks held by kworker/u5:4/6297: #0: ffff8881153ea938 ((wq_completion)knbd2-recv){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #0: ffff8881153ea938 ((wq_completion)knbd2-recv){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #0: ffff8881153ea938 ((wq_completion)knbd2-recv){+.+.}-{0:0}, at: process_one_work+0x1e6/0x600 kernel/workqueue.c:2243 #1: ffffc900001e3e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:615 [inline] #1: ffffc900001e3e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:643 [inline] #1: ffffc900001e3e70 ((work_completion)(&args->work)){+.+.}-{0:0}, at: process_one_work+0x1e6/0x600 kernel/workqueue.c:2243 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1100 Comm: khungtaskd Not tainted 5.10.0-rc5-syzkaller #0 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+0xa3/0xc8 lib/dump_stack.c:118 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 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 458 Comm: kworker/u4:4 Not tainted 5.10.0-rc5-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: bat_events batadv_nc_worker RIP: 0010:arch_local_irq_restore arch/x86/include/asm/paravirt.h:653 [inline] RIP: 0010:lock_release+0x180/0x310 kernel/locking/lockdep.c:5460 Code: 02 ba ff ff ff ff 65 0f c1 15 dc 49 dc 7e 83 fa 01 0f 85 48 01 00 00 48 83 3d 53 fe 48 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 RSP: 0018:ffffc90000e33de0 EFLAGS: 00000282 RAX: 0000000000000000 RBX: ffff888100a6c000 RCX: ffffc90000e33dec RDX: 0000000000000001 RSI: ffffffff840a269f RDI: 0000000000000282 RBP: 0000000000000282 R08: 0000000000000001 R09: 0000000000000000 R10: ffff888100a6c918 R11: 0000000000000000 R12: ffffffff847fbf40 R13: ffffffff8313ae02 R14: 0000000000000003 R15: ffffffff8313ad79 FS: 0000000000000000(0000) GS:ffff888237c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ff9bafc3000 CR3: 000000010799e005 CR4: 00000000001706f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: rcu_lock_release include/linux/rcupdate.h:253 [inline] rcu_read_unlock include/linux/rcupdate.h:695 [inline] batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:411 [inline] batadv_nc_worker+0xde/0x240 net/batman-adv/network-coding.c:718 process_one_work+0x273/0x600 kernel/workqueue.c:2272 worker_thread+0x38/0x380 kernel/workqueue.c:2418 kthread+0x145/0x170 kernel/kthread.c:292 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:296