syzbot

INFO: task kworker/u8:0:12 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:0    state:D stack:20584 pid:12    tgid:12    ppid:2      task_flags:0x4208060 flags:0x00004000
Workqueue: writeback wb_workfn (flush-7:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5357 [inline]
 __schedule+0x16f3/0x4c20 kernel/sched/core.c:6961
 __schedule_loop kernel/sched/core.c:7043 [inline]
 rt_mutex_schedule+0x77/0xf0 kernel/sched/core.c:7339
 rt_mutex_slowlock_block kernel/locking/rtmutex.c:1647 [inline]
 __rt_mutex_slowlock kernel/locking/rtmutex.c:1721 [inline]
 __rt_mutex_slowlock_locked+0x1e04/0x25e0 kernel/locking/rtmutex.c:1760
 rt_mutex_slowlock+0xb5/0x160 kernel/locking/rtmutex.c:1800
 __rt_mutex_lock kernel/locking/rtmutex.c:1815 [inline]
 rwbase_write_lock+0x14f/0x750 kernel/locking/rwbase_rt.c:244
 f2fs_down_write fs/f2fs/f2fs.h:2234 [inline]
 f2fs_issue_checkpoint+0x39c/0x570 fs/f2fs/checkpoint.c:1846
 f2fs_balance_fs_bg+0x54b/0x9c0 fs/f2fs/segment.c:544
 f2fs_write_node_pages+0x146/0x6e0 fs/f2fs/node.c:2193
 do_writepages+0x32b/0x550 mm/page-writeback.c:2634
 __writeback_single_inode+0x145/0x1000 fs/fs-writeback.c:1680
 writeback_sb_inodes+0x6b7/0xf60 fs/fs-writeback.c:1976
 __writeback_inodes_wb+0x111/0x240 fs/fs-writeback.c:2047
 wb_writeback+0x44f/0xaf0 fs/fs-writeback.c:2158
 wb_check_old_data_flush fs/fs-writeback.c:2262 [inline]
 wb_do_writeback fs/fs-writeback.c:2315 [inline]
 wb_workfn+0xaf4/0xf00 fs/fs-writeback.c:2343
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0xade/0x17b0 kernel/workqueue.c:3319
 worker_thread+0x8a0/0xda0 kernel/workqueue.c:3400
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Showing all locks held in the system:
4 locks held by kworker/u8:0/12:
 #0: ffff8881404cb138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff8881404cb138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc90000117bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc90000117bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffff88803afc80d0 (&type->s_umount_key#54){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0 fs/super.c:563
 #3: ffff888033871990 (&sbi->gc_lock){+.+.}-{4:4}, at: f2fs_down_write fs/f2fs/f2fs.h:2234 [inline]
 #3: ffff888033871990 (&sbi->gc_lock){+.+.}-{4:4}, at: f2fs_issue_checkpoint+0x39c/0x570 fs/f2fs/checkpoint.c:1846
1 lock held by khungtaskd/38:
 #0: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8d9a8b80 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6775
4 locks held by kworker/u8:8/1111:
 #0: ffff8881404cb138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff8881404cb138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc90004e97bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc90004e97bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffff8880322ca0d0 (&type->s_umount_key#54){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0 fs/super.c:563
 #3: ffff8880384f9990 (&sbi->gc_lock){+.+.}-{4:4}, at: f2fs_down_write fs/f2fs/f2fs.h:2234 [inline]
 #3: ffff8880384f9990 (&sbi->gc_lock){+.+.}-{4:4}, at: f2fs_issue_checkpoint+0x39c/0x570 fs/f2fs/checkpoint.c:1846
4 locks held by kworker/u8:10/1161:
 #0: ffff8881404cb138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3211 [inline]
 #0: ffff8881404cb138 ((wq_completion)writeback){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3319
 #1: ffffc900050c7bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3212 [inline]
 #1: ffffc900050c7bc0 ((work_completion)(&(&wb->dwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3319
 #2: ffff8880276300d0 (&type->s_umount_key#54){++++}-{4:4}, at: super_trylock_shared+0x20/0xf0 fs/super.c:563
 #3: ffff888027359990 (&sbi->gc_lock){+.+.}-{4:4}, at: f2fs_down_write fs/f2fs/f2fs.h:2234 [inline]
 #3: ffff888027359990 (&sbi->gc_lock){+.+.}-{4:4}, at: f2fs_issue_checkpoint+0x39c/0x570 fs/f2fs/checkpoint.c:1846
1 lock held by udevd/5207:
2 locks held by getty/5600:
 #0: ffff88823bf280a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90003e762e0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x444/0x1410 drivers/tty/n_tty.c:2222
5 locks held by syz.0.17/6122:
6 locks held by syz.1.18/6152:
7 locks held by syz.2.19/6177:
1 lock held by syz-executor/6181:

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 38 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x39e/0x3d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:328 [inline]
 watchdog+0xf93/0xfe0 kernel/hung_task.c:491
 kthread+0x711/0x8a0 kernel/kthread.c:463
 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 6177 Comm: syz.2.19 Not tainted syzkaller #0 PREEMPT_{RT,(full)} 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
RIP: 0010:match_held_lock+0x15/0xc0 kernel/locking/lockdep.c:5309
Code: 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 41 56 53 bb 01 00 00 00 48 39 77 10 74 6a 81 7f 20 00 00 20 00 <72> 5f 48 8b 46 08 48 85 c0 75 17 31 db 49 89 fe 48 89 f7 31 f6 e8
RSP: 0018:ffffc90003e8f3e0 EFLAGS: 00000083
RAX: 0000000000000009 RBX: 0000000000000001 RCX: 6e1bbcc47dce7b00
RDX: 0000000000000001 RSI: ffff8880566c3998 RDI: ffff8880259f0c10
RBP: 00000000ffffffff R08: 0000000000000003 R09: 0000000000000004
R10: dffffc0000000000 R11: fffff520007d1eb0 R12: 0000000000000046
R13: ffff8880259f0000 R14: ffff8880566c3998 R15: 0000000000000006
FS:  0000555578998500(0000) GS:ffff8881269c2000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f86a9e01190 CR3: 000000003acde000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 __lock_is_held kernel/locking/lockdep.c:5601 [inline]
 lock_is_held_type+0xa8/0x190 kernel/locking/lockdep.c:5940
 lock_is_held include/linux/lockdep.h:249 [inline]
 rtlock_slowlock_locked+0xba/0x4010 kernel/locking/rtmutex.c:1836
 rtlock_slowlock kernel/locking/rtmutex.c:1895 [inline]
 rtlock_lock kernel/locking/spinlock_rt.c:43 [inline]
 __rt_spin_lock kernel/locking/spinlock_rt.c:49 [inline]
 rt_spin_lock+0x152/0x2c0 kernel/locking/spinlock_rt.c:57
 spin_lock include/linux/spinlock_rt.h:44 [inline]
 igrab+0x21/0xb0 fs/inode.c:1540
 f2fs_sync_inode_meta fs/f2fs/checkpoint.c:1149 [inline]
 block_operations fs/f2fs/checkpoint.c:1263 [inline]
 f2fs_write_checkpoint+0xaea/0x1df0 fs/f2fs/checkpoint.c:1638
 f2fs_issue_checkpoint+0x3ac/0x570 fs/f2fs/checkpoint.c:1847
 f2fs_unlink+0x5eb/0xac0 fs/f2fs/namei.c:603
 vfs_unlink+0x39a/0x660 fs/namei.c:4586
 do_unlinkat+0x345/0x570 fs/namei.c:4650
 __do_sys_unlink fs/namei.c:4696 [inline]
 __se_sys_unlink fs/namei.c:4694 [inline]
 __x64_sys_unlink+0x47/0x50 fs/namei.c:4694
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8bde53ebe9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff24f5d888 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 00007f8bde775fa0 RCX: 00007f8bde53ebe9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000200000000440
RBP: 00007f8bde5c1e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8bde775fa0 R14: 00007f8bde775fa0 R15: 0000000000000001
 </TASK>