INFO: task syz-executor1:5452 blocked for more than 120 seconds. Not tainted 4.9.67-gf26d3c7 #106 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor1 D28080 5452 3501 0x00000004 ffff8801d902e000 ffff8801ce15a4c0 ffff8801cecd0a80 ffff8801c9810000 ffff8801db321418 ffff8801d4c77b10 ffffffff838981cb ffffffff81239470 ffff8801d4c77bb8 00ffffff81cfbaca ffff8801db321ce8 ffff8801db321d10 Call Trace: [] schedule+0x7f/0x1b0 kernel/sched/core.c:3550 [] schedule_timeout+0x643/0x1220 kernel/time/timer.c:1770 [] io_schedule_timeout+0x1be/0x390 kernel/sched/core.c:5172 [] do_wait_for_common kernel/sched/completion.c:75 [inline] [] __wait_for_common kernel/sched/completion.c:93 [inline] [] wait_for_common_io kernel/sched/completion.c:107 [inline] [] wait_for_completion_io+0x20e/0x2e0 kernel/sched/completion.c:155 [] submit_bio_wait+0x11b/0x180 block/bio.c:885 [] blkdev_issue_flush+0x157/0x220 block/blk-flush.c:518 [] blkdev_fsync+0x85/0xb0 fs/block_dev.c:378 [] vfs_fsync_range+0x10a/0x250 fs/sync.c:195 [] vfs_fsync fs/sync.c:209 [inline] [] do_fsync+0x42/0xb0 fs/sync.c:219 [] SYSC_fsync fs/sync.c:228 [inline] [] SyS_fsync+0x16/0x20 fs/sync.c:226 [] entry_SYSCALL_64_fastpath+0x23/0xc6 Showing all locks held in the system: 2 locks held by khungtaskd/514: #0: (rcu_read_lock){......}, at: [] check_hung_uninterruptible_tasks kernel/hung_task.c:168 [inline] #0: (rcu_read_lock){......}, at: [] watchdog+0x125/0xa70 kernel/hung_task.c:239 #1: (tasklist_lock){.+.+..}, at: [] debug_show_all_locks+0x70/0x280 kernel/locking/lockdep.c:4336 2 locks held by getty/3247: #0: (&tty->ldisc_sem){++++++}, at: [] ldsem_down_read+0x32/0x40 drivers/tty/tty_ldsem.c:367 #1: (&ldata->atomic_read_lock){+.+...}, at: [] n_tty_read+0x1f4/0x16c0 drivers/tty/n_tty.c:2133 1 lock held by syz-executor0/5480: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 1 lock held by syz-executor0/5488: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 1 lock held by syz-executor3/5512: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 1 lock held by syz-executor3/5522: #0: (&lo->lo_ctl_mutex/1){+.+.+.}, at: [] lo_ioctl+0x8f/0x1990 drivers/block/loop.c:1337 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 514 Comm: khungtaskd Not tainted 4.9.67-gf26d3c7 #106 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 ffff8801d8d1fd00 ffffffff81d906e9 0000000000000000 0000000000000001 0000000000000001 0000000000000001 ffffffff810ba170 ffff8801d8d1fd38 ffffffff81d9b80d 0000000000000001 0000000000000000 ffff8801cf76e418 Call Trace: [] __dump_stack lib/dump_stack.c:15 [inline] [] dump_stack+0xc1/0x128 lib/dump_stack.c:51 [] nmi_cpu_backtrace+0xfd/0x120 lib/nmi_backtrace.c:99 [] nmi_trigger_cpumask_backtrace+0x117/0x190 lib/nmi_backtrace.c:60 [] arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:37 [] trigger_all_cpu_backtrace include/linux/nmi.h:58 [inline] [] check_hung_task kernel/hung_task.c:125 [inline] [] check_hung_uninterruptible_tasks kernel/hung_task.c:182 [inline] [] watchdog+0x6f0/0xa70 kernel/hung_task.c:239 [] kthread+0x26d/0x300 kernel/kthread.c:211 [] ret_from_fork+0x2a/0x40 arch/x86/entry/entry_64.S:433 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.67-gf26d3c7 #106 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 task: ffffffff84426880 task.stack: ffffffff84400000 RIP: 0010:[] c [] tick_nohz_irq_enter kernel/time/tick-sched.c:1124 [inline] RIP: 0010:[] c [] tick_irq_enter+0x4a/0x220 kernel/time/tick-sched.c:1150 RSP: 0018:ffff8801db207f90 EFLAGS: 00000046 RAX: 0000000000000000 RBX: 000000000001a680 RCX: 1ffffffff083f67c RDX: dffffc0000000000 RSI: ffffffff83c17780 RDI: ffffffff841fb3e0 RBP: ffff8801db207fb8 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000 R13: ffffffff84a2e6f8 R14: 0000000000000000 R15: 0000000000000000 FS: 0000000000000000(0000) GS:ffff8801db200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000006cc000 CR3: 00000001d1ace000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Stack: ffff8801db207fb8c ffffffff84426880c 0000000000000000c ffffffff84a2e6f8c 0000000000000000c ffff8801db207fd0c ffffffff81144cd3c ffffffff84a1f5e8c ffff8801db207fe8c ffffffff838add3ac ffffffff84a1f5e8c ffffffff84407dc0c Call Trace: d [] irq_enter+0xb3/0xd0 kernel/softirq.c:345 [] smp_reschedule_interrupt+0xa/0x80 arch/x86/kernel/smp.c:264 [] reschedule_interrupt+0x8c/0xa0 arch/x86/entry/entry_64.S:732 d [] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53 [] arch_safe_halt arch/x86/include/asm/paravirt.h:103 [inline] [] default_idle+0x55/0x360 arch/x86/kernel/process.c:295 [] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286 [] default_idle_call+0x36/0x60 kernel/sched/idle.c:97 [] cpuidle_idle_call kernel/sched/idle.c:155 [inline] [] cpu_idle_loop kernel/sched/idle.c:248 [inline] [] cpu_startup_entry+0x2b0/0x380 kernel/sched/idle.c:303 [] rest_init+0x184/0x190 init/main.c:407 [] start_kernel+0x679/0x6ae init/main.c:661 [] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196 [] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:177 Code: cff ce8 c0b cfd cb1 c00 c48 cba c00 c00 c00 c00 c00 cfc cff cdf c89 cc0 c48 c8d c3c cc5 ce0 cb3 c1f c84 c48 c89 cf9 c48 cc1 ce9 c03 c80 c3c c11 c00 c0f c85 cc3 c01 c00 c00 c<48> c03 c1c cc5 ce0 cb3 c1f c84 c48 cb8 c00 c00 c00 c00 c00 cfc cff cdf c4c c8d cab c