INFO: task hung in io_write

Status: upstream: reported C repro on 2026/09/08 22:08
Subsystems: io-uring ext4
Labels: prio:high
[Documentation on labels]
Reported-by: syzbot+2eb3d983669d3e49d4fa@syzkaller.appspotmail.com
First crash: 1d13h, last: 1d13h
▶ ▼ ✨ AI Jobs (1)
ID Workflow Result Correct Bug Created Started Finished Revision
8bda2084 assessment-security DenialOfService: ✅ Exploitable: ❌ FilesystemTrigger: ❌ NetworkTrigger: ❌ PeripheralTrigger: ❌ RemoteTrigger: ❌ Unprivileged: ✅ UserNamespace: ✅ VMGuestTrigger: ❌ VMHostTrigger: ❌ ❓ INFO: task hung in io_write 2026/09/08 05:06 2026/09/08 05:07 2026/09/08 05:51 680aa3e1
▶ ▼ Discussions (2)
Title Replies (including bot) Last reply
[syzbot] [io-uring?] [ext4?] INFO: task hung in io_write 4 (9) 2026/09/09 12:13
[PATCH] io_uring/rw: end write accounting from ->ki_complete 1 (1) 2026/09/09 01:09
▶ ▼ Last patch testing requests (4)
Created Duration User Patch Repo Result
2026/09/09 11:46 25m axboe@kernel.dk git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git syztest no crash job log log
2026/09/09 11:02 24m axboe@kernel.dk git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git io_uring-7.3 error job log
2026/09/09 01:15 22m axboe@kernel.dk git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git io_uring-7.3 error job log
2026/09/09 01:10 24m axboe@kernel.dk git://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git io_uring-7.3 error job log

Sample crash report:
INFO: task iou-wrk-5725:5730 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:iou-wrk-5725    state:D stack:22112 pid:5730  tgid:5724  ppid:5438   task_flags:0x404050 flags:0x00080002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5526 [inline]
 __schedule+0x17db/0x58f0 kernel/sched/core.c:7276
 __schedule_loop kernel/sched/core.c:7353 [inline]
 schedule+0x164/0x2b0 kernel/sched/core.c:7368
 percpu_rwsem_wait+0x326/0x490 kernel/locking/percpu-rwsem.c:164
 __percpu_down_read+0xee/0x130 kernel/locking/percpu-rwsem.c:180
 percpu_down_read_internal include/linux/percpu-rwsem.h:67 [inline]
 percpu_down_read_freezable include/linux/percpu-rwsem.h:83 [inline]
 __sb_start_write include/linux/fs/super.h:19 [inline]
 sb_start_write include/linux/fs/super.h:125 [inline]
 kiocb_start_write include/linux/fs.h:2787 [inline]
 io_kiocb_start_write io_uring/rw.c:1109 [inline]
 io_write+0x120c/0x1680 io_uring/rw.c:1163
 __io_issue_sqe+0x188/0x4d0 io_uring/io_uring.c:1386
 io_issue_sqe+0x16d/0x1020 io_uring/io_uring.c:1409
 io_wq_submit_work+0x7ab/0xc90 io_uring/io_uring.c:1525
 io_worker_handle_work+0x7a1/0x1140 io_uring/io-wq.c:659
 io_wq_worker+0x452/0xf10 io_uring/io-wq.c:714
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Showing all locks held in the system:
locks held by kworker/u4:1/13: 2, last CPU#0:
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #1: ffffc9000026fc40 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc9000026fc40 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc9000026fc40 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #1: ffffc9000026fc40 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
locks held by khungtaskd/26: 1, last CPU#0:
 #0: ffffffff8ed5c760 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffffffff8ed5c760 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8ed5c760 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6871
locks held by kworker/u4:2/37: 3, last CPU#0:
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #1: ffffc900003f7c40 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc900003f7c40 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc900003f7c40 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #1: ffffc900003f7c40 ((work_completion)(&(&nsim_dev->trap_data->trap_report_dw)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #2: ffff888051872258 (&devlink->lock_key#4){+.+.}-{4:4}, at: nsim_dev_trap_report_work+0x57/0xb40 drivers/net/netdevsim/dev.c:834
locks held by kworker/u4:3/43: 2, on CPU#0:
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #0: ffff88801b094140 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #1: ffffc90000877c40 ((work_completion)(&(&kfence_timer)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc90000877c40 ((work_completion)(&(&kfence_timer)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc90000877c40 ((work_completion)(&(&kfence_timer)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #1: ffffc90000877c40 ((work_completion)(&(&kfence_timer)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
locks held by kworker/u4:7/187: 4, last CPU#0:
 #0: ffff88803fa20140 ((wq_completion)bat_events){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff88803fa20140 ((wq_completion)bat_events){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff88803fa20140 ((wq_completion)bat_events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #0: ffff88803fa20140 ((wq_completion)bat_events){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #1: ffffc900019dfc40 ((work_completion)(&(&forw_packet_aggr->delayed_work)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc900019dfc40 ((work_completion)(&(&forw_packet_aggr->delayed_work)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc900019dfc40 ((work_completion)(&(&forw_packet_aggr->delayed_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #1: ffffc900019dfc40 ((work_completion)(&(&forw_packet_aggr->delayed_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #2: ffff88801fc3bb20 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x2d/0x160 kernel/sched/core.c:677
 #3: ffff88801fc24408 (psi_seq){-.-.}-{0:0}, at: psi_task_switch+0x57/0x7d0 kernel/sched/psi.c:933
locks held by getty/5086: 2, on CPU#0:
 #0: ffff88803ee570a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc90000d202e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
locks held by kworker/0:10/5721: 3, last CPU#0:
 #0: ffff88801b0a8940 ((wq_completion)events){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #0: ffff88801b0a8940 ((wq_completion)events){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffff88801b0a8940 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #0: ffff88801b0a8940 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #1: ffffc900052f7c40 ((work_completion)(&adapter->watchdog_task)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:309 [inline]
 #1: ffffc900052f7c40 ((work_completion)(&adapter->watchdog_task)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #1: ffffc900052f7c40 ((work_completion)(&adapter->watchdog_task)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3361 [inline]
 #1: ffffc900052f7c40 ((work_completion)(&adapter->watchdog_task)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3479
 #2: ffff88801fc26118 (&base->lock){-.-.}-{2:2}, at: lock_timer_base kernel/time/timer.c:1004 [inline]
 #2: ffff88801fc26118 (&base->lock){-.-.}-{2:2}, at: __mod_timer+0x1a9/0xed0 kernel/time/timer.c:1085
locks held by syz.0.23/5725: 2, on CPU#0:
 #0: ffff88801d025220 (&bdev->bd_fsfreeze_mutex){+.+.}-{4:4}, at: bdev_freeze+0x33/0x2f0 block/bdev.c:304
 #1: ffff888048fa4460 (sb_writers#4){++++}-{0:0}, at: sb_wait_write fs/super.c:2043 [inline]
 #1: ffff888048fa4460 (sb_writers#4){++++}-{0:0}, at: freeze_super+0x4f4/0x11c0 fs/super.c:2307
locks held by iou-wrk-5725/5730: 1, on CPU#0:
 #0: ffff888048fa4460 (sb_writers#4){++++}-{0:0}, at: __io_issue_sqe+0x188/0x4d0 io_uring/io_uring.c:1386

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 26 Comm: khungtaskd Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:123
 nmi_trigger_cpumask_backtrace+0x17d/0x390 lib/nmi_backtrace.c:66
 trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline]
 __sys_info lib/sys_info.c:157 [inline]
 sys_info+0x135/0x170 lib/sys_info.c:165
 check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
 watchdog+0xfd7/0x1030 kernel/hung_task.c:561
 kthread+0x38b/0x480 kernel/kthread.c:436
 ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/08 05:06 upstream 28924df2a08f 680aa3e1 .config console log report syz / log C [disk image (non-bootable)] [vmlinux] [kernel image] [mounted in repro (clean fs)] ci-snapshot-upstream-root INFO: task hung in io_write
* Struck through repros no longer work on HEAD.