INFO: task kworker/u4:0:5 blocked for more than 140 seconds. Not tainted 4.14.295-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. kworker/u4:0 D25976 5 2 0x80000000 Workqueue: writeback wb_workfn (flush-7:2) Call Trace: context_switch kernel/sched/core.c:2811 [inline] __schedule+0x88b/0x1de0 kernel/sched/core.c:3387 schedule+0x8d/0x1b0 kernel/sched/core.c:3431 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:3489 __mutex_lock_common kernel/locking/mutex.c:833 [inline] __mutex_lock+0x669/0x1310 kernel/locking/mutex.c:893 f2fs_balance_fs+0x412/0x5a0 fs/f2fs/segment.c:435 __write_data_page+0x646/0x1480 fs/f2fs/data.c:1615 f2fs_write_cache_pages+0x40d/0xe50 fs/f2fs/data.c:1744 __f2fs_write_data_pages+0x2e2/0xb90 fs/f2fs/data.c:1838 do_writepages+0xc3/0x240 mm/page-writeback.c:2361 __writeback_single_inode+0xda/0x1010 fs/fs-writeback.c:1382 writeback_sb_inodes+0x48b/0xd30 fs/fs-writeback.c:1645 __writeback_inodes_wb+0xbf/0x230 fs/fs-writeback.c:1716 wb_writeback+0x710/0xb80 fs/fs-writeback.c:1822 wb_check_old_data_flush fs/fs-writeback.c:1935 [inline] wb_do_writeback fs/fs-writeback.c:1959 [inline] wb_workfn+0x708/0xf50 fs/fs-writeback.c:1988 process_one_work+0x793/0x14a0 kernel/workqueue.c:2117 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2251 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Showing all locks held in the system: IPVS: ftp: loaded support on port[0] = 21 4 locks held by kworker/u4:0/5: #0: ("writeback"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2088 #1: ((&(&wb->dwork)->work)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2092 #2: (&type->s_umount_key#71){++++}, at: [] trylock_super+0x1b/0xe0 fs/super.c:402 #3: (&sbi->gc_mutex){+.+.}, at: [] f2fs_balance_fs+0x412/0x5a0 fs/f2fs/segment.c:435 4 locks held by kworker/u4:2/35: #0: ("writeback"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2088 #1: ((&(&wb->dwork)->work)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2092 #2: (&type->s_umount_key#71){++++}, at: [] trylock_super+0x1b/0xe0 fs/super.c:402 #3: (&sbi->gc_mutex){+.+.}, at: [] f2fs_balance_fs+0x412/0x5a0 fs/f2fs/segment.c:435 1 lock held by khungtaskd/1533: #0: (tasklist_lock){.+.+}, at: [] debug_show_all_locks+0x7c/0x21a kernel/locking/lockdep.c:4548 2 locks held by syz-executor.3/11363: #0: (&type->s_umount_key#71){++++}, at: [] iterate_supers+0xda/0x490 fs/super.c:611 #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:338 [inline] #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] sync_inodes_sb+0x156/0x880 fs/fs-writeback.c:2445 2 locks held by syz-executor.3/11369: #0: (&type->s_umount_key#71){++++}, at: [] iterate_supers+0xda/0x490 fs/super.c:611 #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:338 [inline] #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] sync_inodes_sb+0x156/0x880 fs/fs-writeback.c:2445 2 locks held by syz-executor.2/11645: #0: (&type->s_umount_key#71){++++}, at: [] iterate_supers+0xda/0x490 fs/super.c:611 #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:338 [inline] #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] sync_inodes_sb+0x156/0x880 fs/fs-writeback.c:2445 2 locks held by syz-executor.2/11647: #0: (&type->s_umount_key#71){++++}, at: [] iterate_supers+0xda/0x490 fs/super.c:611 #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:338 [inline] #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] sync_inodes_sb+0x156/0x880 fs/fs-writeback.c:2445 2 locks held by syz-executor.3/11915: #0: (&type->s_umount_key#71){++++}, at: [] iterate_supers+0xda/0x490 fs/super.c:611 #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:338 [inline] #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] sync_inodes_sb+0x156/0x880 fs/fs-writeback.c:2445 2 locks held by syz-executor.3/11921: #0: (&type->s_umount_key#71){++++}, at: [] iterate_supers+0xda/0x490 fs/super.c:611 #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:338 [inline] #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] sync_inodes_sb+0x156/0x880 fs/fs-writeback.c:2445 2 locks held by syz-executor.2/12210: #0: (&type->s_umount_key#71){++++}, at: [] iterate_supers+0xda/0x490 fs/super.c:611 #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:338 [inline] #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] sync_inodes_sb+0x156/0x880 fs/fs-writeback.c:2445 2 locks held by syz-executor.2/12213: #0: (&type->s_umount_key#71){++++}, at: [] iterate_supers+0xda/0x490 fs/super.c:611 #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] bdi_down_write_wb_switch_rwsem fs/fs-writeback.c:338 [inline] #1: (&bdi->wb_switch_rwsem){+.+.}, at: [] sync_inodes_sb+0x156/0x880 fs/fs-writeback.c:2445 2 locks held by kworker/u4:6/12701: #0: ("events_unbound"){+.+.}, at: [] process_one_work+0x6b0/0x14a0 kernel/workqueue.c:2088 #1: ((&sub_info->work)){+.+.}, at: [] process_one_work+0x6e6/0x14a0 kernel/workqueue.c:2092 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1533 Comm: khungtaskd Not tainted 4.14.295-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 Call Trace: __dump_stack lib/dump_stack.c:17 [inline] dump_stack+0x1b2/0x281 lib/dump_stack.c:58 nmi_cpu_backtrace.cold+0x57/0x93 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0x13a/0x180 lib/nmi_backtrace.c:62 trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline] watchdog+0x5b9/0xb40 kernel/hung_task.c:274 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 CPU: 0 PID: 4620 Comm: kworker/0:2 Not tainted 4.14.295-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/11/2022 Workqueue: events wait_rcu_exp_gp task: ffff8880a1b52040 task.stack: ffff8880a18c8000 RIP: 0010:preempt_latency_start kernel/sched/core.c:3090 [inline] RIP: 0010:preempt_count_add+0xc3/0x170 kernel/sched/core.c:3113 RSP: 0018:ffff8880a18cfb88 EFLAGS: 00000017 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff8880a1b53278 RBP: ffff8880a1b52040 R08: ffffffff8b9b7120 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000286 R13: 1ffff11014319f79 R14: dffffc0000000000 R15: dffffc0000000000 FS: 0000000000000000(0000) GS:ffff8880ba400000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007f024d8e01b8 CR3: 00000000ab28a000 CR4: 00000000003406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:109 [inline] _raw_spin_lock_irqsave+0x70/0xc0 kernel/locking/spinlock.c:160 prepare_to_swait+0x5c/0x2a0 kernel/sched/swait.c:81 prepare_to_swait_event+0x40/0xb0 kernel/sched/swait.c:93 synchronize_sched_expedited_wait kernel/rcu/tree_exp.h:450 [inline] rcu_exp_wait_wake+0x150/0x520 kernel/rcu/tree_exp.h:518 process_one_work+0x793/0x14a0 kernel/workqueue.c:2117 worker_thread+0x5cc/0xff0 kernel/workqueue.c:2251 kthread+0x30d/0x420 kernel/kthread.c:232 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404 Code: ff ff 7f 39 c5 74 03 5b 5d c3 48 8b 5c 24 10 48 89 df e8 a1 da 08 00 85 c0 75 31 65 48 8b 2c 25 c0 7f 02 00 48 8d bd 38 12 00 00 <48> b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 80 3c 02 00