INFO: task hung in io_wq_put_and_exit

Status: upstream: reported C repro on 2025/06/25 22:50
Bug presence: origin:lts-only
[Documentation on labels]
Reported-by: syzbot+ea8018030af6aec75b1e@syzkaller.appspotmail.com
First crash: 417d, last: 2d19h
Fix commit to backport (bisect log) :
tree: upstream
commit bcb0fda3c2da9fe4721d3e73d80e778c038e7d27
Author: Jens Axboe <axboe@kernel.dk>
Date: Wed Mar 5 21:03:34 2025 +0000

  io_uring/rw: ensure reissue path is correctly handled for IOPOLL

  
Bug presence (2)
Date Name Commit Repro Result
2025/12/31 linux-6.6.y (ToT) 5fa4793a2d2d C [report] INFO: task hung in io_wq_put_and_exit
2025/12/31 upstream (ToT) dbf8fe85a16a C Didn't crash
Similar bugs (8)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in io_wq_put_and_exit (6) io-uring 1 syz, C error 74 204d 363d 29/29 fixed on 2026/05/06 16:40
linux-5.15 INFO: task hung in io_wq_put_and_exit 1 1 888d 888d 0/3 auto-obsoleted due to no activity on 2024/06/19 08:55
upstream INFO: task hung in io_wq_put_and_exit (3) io-uring 1 syz, C error unreliable 75 1212d 1607d 0/29 auto-obsoleted due to no activity on 2023/08/20 08:26
upstream INFO: task hung in io_wq_put_and_exit io-uring fs 1 syz, C unreliable 628 1742d 1803d 20/29 fixed on 2021/11/10 00:50
upstream INFO: task hung in io_wq_put_and_exit (2) fs 1 22 1710d 1739d 0/29 closed as invalid on 2022/02/08 09:40
upstream INFO: task hung in io_wq_put_and_exit (5) io-uring input usb 1 syz, C done 9 370d 389d 0/29 closed as invalid on 2025/08/13 14:32
upstream INFO: task hung in io_wq_put_and_exit (4) io-uring 1 syz, C unreliable 86 436d 666d 28/29 fixed on 2025/06/10 16:19
linux-6.1 INFO: task hung in io_wq_put_and_exit 1 syz, C 3 10d 12d 0/3 upstream: reported C repro on 2026/08/04 21:15
Last patch testing requests (2)
Created Duration User Patch Repo Result
2025/08/11 15:38 51m sumanth.gavini@yahoo.com patch linux-6.6.y report log
2025/08/10 21:45 23m sumanth.gavini@yahoo.com patch linux-6.6.y report log
Fix bisection attempts (1)
Created Duration User Patch Repo Result
2025/08/07 00:08 9h48m fix candidate upstream OK (1) job log

Sample crash report:
INFO: task syz.0.20:5939 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.20        state:D stack:25512 pid:5939  ppid:5893   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x15ae/0x4660 kernel/sched/core.c:6701
 schedule+0xbd/0x170 kernel/sched/core.c:6775
 schedule_timeout+0xc1/0x2d0 kernel/time/timer.c:2144
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common kernel/sched/completion.c:116 [inline]
 wait_for_common kernel/sched/completion.c:127 [inline]
 wait_for_completion+0x2c6/0x5a0 kernel/sched/completion.c:148
 io_wq_exit_workers io_uring/io-wq.c:1267 [inline]
 io_wq_put_and_exit+0x493/0x820 io_uring/io-wq.c:1295
 io_uring_clean_tctx+0x12f/0x1b0 io_uring/tctx.c:204
 io_uring_cancel_generic+0x610/0x6c0 io_uring/io_uring.c:3507
 io_uring_files_cancel include/linux/io_uring.h:69 [inline]
 do_exit+0x5f4/0x2530 kernel/exit.c:836
 do_group_exit+0x22d/0x2f0 kernel/exit.c:1032
 __do_sys_exit_group kernel/exit.c:1043 [inline]
 __se_sys_exit_group kernel/exit.c:1041 [inline]
 __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1041
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fb4dd99e0d9
RSP: 002b:00007ffc7e42dc08 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fb4dd99e0d9
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffc7e42dc6c R08: 0000000000000000 R09: 00000000000927c0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000003
R13: 00000000000927c0 R14: 0000000000018a21 R15: 00007ffc7e42dcc0
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:334 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:786 [inline]
 #0: ffffffff8d131da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x290 kernel/locking/lockdep.c:6633
2 locks held by kworker/u4:9/1102:
2 locks held by getty/5534:
 #0: ffff88814d2ac0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x428/0x1370 drivers/tty/n_tty.c:2217
2 locks held by dhcpcd/6134:
 #0: ffff88805afbc130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: lock_sock include/net/sock.h:1780 [inline]
 #0: ffff88805afbc130 (sk_lock-AF_PACKET){+.+.}-{0:0}, at: packet_do_bind+0x33/0xd40 net/packet/af_packet.c:3264
 #1: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:292 [inline]
 #1: ffffffff8d137778 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x306/0x880 kernel/rcu/tree_exp.h:1004

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

NMI backtrace for cpu 1
CPU: 1 PID: 29 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3a6/0x3e0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x17a/0x2f0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:222 [inline]
 watchdog+0xf59/0xfa0 kernel/hung_task.c:379
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 1145 Comm: kworker/u4:11 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_unbound nsim_dev_trap_report_work
RIP: 0010:check_region_inline mm/kasan/generic.c:-1 [inline]
RIP: 0010:kasan_check_range+0x12/0x290 mm/kasan/generic.c:187
Code: 0f 0b b8 ea ff ff ff c3 0f 0b b8 ea ff ff ff c3 cc cc cc cc cc cc cc cc 66 0f 1f 00 b0 01 48 85 f6 0f 84 b4 01 00 00 55 41 57 <41> 56 41 55 41 54 53 4c 8d 04 37 49 39 f8 0f 82 13 02 00 00 49 89
RSP: 0018:ffffc900048df4c8 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 0000000000000003 RCX: ffffffff816893c2
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff911ed5e8
RBP: ffffc900048df728 R08: dffffc0000000000 R09: 1ffffffff223dac1
R10: dffffc0000000000 R11: fffffbfff223dac2 R12: 0000000000000003
R13: ffff888023da0b80 R14: 000000000000077a R15: ffff888023da0b80
FS:  0000000000000000(0000) GS:ffff8880b8e00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e63eb79660 CR3: 000000002f542000 CR4: 00000000003506f0
Call Trace:
 <TASK>
 instrument_atomic_read include/linux/instrumented.h:68 [inline]
 _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline]
 hlock_class kernel/locking/lockdep.c:228 [inline]
 check_wait_context kernel/locking/lockdep.c:4798 [inline]
 __lock_acquire+0x952/0x7d80 kernel/locking/lockdep.c:5087
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0xb4/0x100 kernel/locking/spinlock.c:162
 __debug_check_no_obj_freed lib/debugobjects.c:1034 [inline]
 debug_check_no_obj_freed+0x9e/0x520 lib/debugobjects.c:1075
 slab_free_hook mm/slub.c:1786 [inline]
 slab_free_freelist_hook+0xd2/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
 skb_kfree_head net/core/skbuff.c:946 [inline]
 skb_free_head net/core/skbuff.c:958 [inline]
 skb_release_data+0x609/0x7f0 net/core/skbuff.c:988
 skb_release_all net/core/skbuff.c:1054 [inline]
 __kfree_skb net/core/skbuff.c:1068 [inline]
 consume_skb+0xb2/0x110 net/core/skbuff.c:1284
 nsim_dev_trap_report drivers/net/netdevsim/dev.c:821 [inline]
 nsim_dev_trap_report_work+0x723/0xa90 drivers/net/netdevsim/dev.c:851
 process_one_work kernel/workqueue.c:2657 [inline]
 process_scheduled_works+0xa60/0x1600 kernel/workqueue.c:2734
 worker_thread+0xa5e/0xfe0 kernel/workqueue.c:2815
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293
 </TASK>

Crashes (17):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/14 08:59 linux-6.6.y d27334b2888c b13552fe .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/03/23 02:00 linux-6.6.y 4fc00fe35d46 5b92003d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/12/29 04:08 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/02/05 06:16 linux-6.6.y 2cf6f68313dc ea10c935 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/10/25 07:05 linux-6.6.y 4a243110dc88 c0460fcd .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/08/10 16:04 linux-6.6.y 3a8ababb8b6a 32a0e5ed .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/06/25 22:50 linux-6.6.y 6282921b6825 26d77996 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/08/13 23:52 linux-6.6.y d27334b2888c b13552fe .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/08/05 02:04 linux-6.6.y aa0e49877a2e d4abbeac .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/06/01 07:09 linux-6.6.y 0a40c6fbd105 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/05/31 13:39 linux-6.6.y 0a40c6fbd105 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/05/30 22:50 linux-6.6.y 0a40c6fbd105 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/05/30 11:10 linux-6.6.y 0a40c6fbd105 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/05/30 11:07 linux-6.6.y 0a40c6fbd105 6b4a8443 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2026/04/13 03:15 linux-6.6.y 8cee53b8eaeb 38c8e246 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/12/28 23:03 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
2025/12/11 22:23 linux-6.6.y 5fa4793a2d2d d6526ea3 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan INFO: task hung in io_wq_put_and_exit
* Struck through repros no longer work on HEAD.