[syzbot] [input?] [usb?] [io-uring?] INFO: task hung in io_wq_put_and_exit (5)

[syzbot] [input?] [usb?] [io-uring?] INFO: task hung in io_wq_put_and_exit (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    bf61759db409 Merge tag 'sched_ext-for-6.16-rc6-fixes' of g..
git tree:       upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=12b877d4580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=415e83411fefd73f
dashboard link: https://syzkaller.appspot.com/bug?extid=e328767eafd849df0a78
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=110b938c580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1622a38c580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/22c5f1286a72/disk-bf61759d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/cc79af4d966c/vmlinux-bf61759d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b2e6d621f424/bzImage-bf61759d.xz

The issue was bisected to:

commit e5598d6ae62626d261b046a2f19347c38681ff51
Author: Pavel Begunkov <asml.silence@gmail.com>
Date:   Thu Aug 24 22:53:31 2023 +0000

    io_uring: compact SQ/CQ heads/tails

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12c92b82580000
final oops:     https://syzkaller.appspot.com/x/report.txt?x=11c92b82580000
console output: https://syzkaller.appspot.com/x/log.txt?x=16c92b82580000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+e328767eafd849df0a78@syzkaller.appspotmail.com
Fixes: e5598d6ae626 ("io_uring: compact SQ/CQ heads/tails")

INFO: task syz-executor971:5849 blocked for more than 143 seconds.
      Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
      Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor971 state:D stack:26488 pid:5849  tgid:5849  ppid:5844   task_flags:0x400148 flags:0x00024002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x116a/0x5de0 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6879
 schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common+0x2ff/0x4e0 kernel/sched/completion.c:116
 io_wq_exit_workers io_uring/io-wq.c:1319 [inline]
 io_wq_put_and_exit+0x271/0x8d0 io_uring/io-wq.c:1347
 io_uring_clean_tctx+0x10d/0x190 io_uring/tctx.c:203
 io_uring_cancel_generic+0x69c/0x9a0 io_uring/io_uring.c:3212
 io_uring_files_cancel include/linux/io_uring.h:19 [inline]
 do_exit+0x2ce/0x2bd0 kernel/exit.c:911
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
 __do_sys_exit_group kernel/exit.c:1116 [inline]
 __se_sys_exit_group kernel/exit.c:1114 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1114
 x64_sys_call+0x1530/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f141ec08e39
RSP: 002b:00007ffcd1b0b6e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f141ec08e39
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 00007f141ec843b0 R08: ffffffffffffffb8 R09: 0000000000000000
R10: 000000000000000e R11: 0000000000000246 R12: 00007f141ec843b0
R13: 0000000000000000 R14: 00007f141ec880c0 R15: 00007f141ebd7020
 </TASK>
INFO: task syz-executor971:5850 blocked for more than 143 seconds.
      Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
      Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor971 state:D stack:26488 pid:5850  tgid:5850  ppid:5846   task_flags:0x400148 flags:0x00024002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x116a/0x5de0 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6879
 schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common+0x2ff/0x4e0 kernel/sched/completion.c:116
 io_wq_exit_workers io_uring/io-wq.c:1319 [inline]
 io_wq_put_and_exit+0x271/0x8d0 io_uring/io-wq.c:1347
 io_uring_clean_tctx+0x10d/0x190 io_uring/tctx.c:203
 io_uring_cancel_generic+0x69c/0x9a0 io_uring/io_uring.c:3212
 io_uring_files_cancel include/linux/io_uring.h:19 [inline]
 do_exit+0x2ce/0x2bd0 kernel/exit.c:911
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
 __do_sys_exit_group kernel/exit.c:1116 [inline]
 __se_sys_exit_group kernel/exit.c:1114 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1114
 x64_sys_call+0x1530/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f141ec08e39
RSP: 002b:00007ffcd1b0b6e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f141ec08e39
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 00007f141ec843b0 R08: ffffffffffffffb8 R09: 0000000000000000
R10: 000000000000000e R11: 0000000000000246 R12: 00007f141ec843b0
R13: 0000000000000000 R14: 00007f141ec880c0 R15: 00007f141ebd7020
 </TASK>
INFO: task syz-executor971:5851 blocked for more than 143 seconds.
      Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
      Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor971 state:D stack:27256 pid:5851  tgid:5851  ppid:5845   task_flags:0x400148 flags:0x00024002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x116a/0x5de0 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6879
 schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common+0x2ff/0x4e0 kernel/sched/completion.c:116
 io_wq_exit_workers io_uring/io-wq.c:1319 [inline]
 io_wq_put_and_exit+0x271/0x8d0 io_uring/io-wq.c:1347
 io_uring_clean_tctx+0x10d/0x190 io_uring/tctx.c:203
 io_uring_cancel_generic+0x69c/0x9a0 io_uring/io_uring.c:3212
 io_uring_files_cancel include/linux/io_uring.h:19 [inline]
 do_exit+0x2ce/0x2bd0 kernel/exit.c:911
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
 __do_sys_exit_group kernel/exit.c:1116 [inline]
 __se_sys_exit_group kernel/exit.c:1114 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1114
 x64_sys_call+0x1530/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f141ec08e39
RSP: 002b:00007ffcd1b0b6e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f141ec08e39
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 00007f141ec843b0 R08: ffffffffffffffb8 R09: 0000000000000000
R10: 000000000000000e R11: 0000000000000246 R12: 00007f141ec843b0
R13: 0000000000000000 R14: 00007f141ec880c0 R15: 00007f141ebd7020
 </TASK>
INFO: task syz-executor971:5852 blocked for more than 144 seconds.
      Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
      Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor971 state:D stack:26312 pid:5852  tgid:5852  ppid:5848   task_flags:0x400148 flags:0x00024002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x116a/0x5de0 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6879
 schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common+0x2ff/0x4e0 kernel/sched/completion.c:116
 io_wq_exit_workers io_uring/io-wq.c:1319 [inline]
 io_wq_put_and_exit+0x271/0x8d0 io_uring/io-wq.c:1347
 io_uring_clean_tctx+0x10d/0x190 io_uring/tctx.c:203
 io_uring_cancel_generic+0x69c/0x9a0 io_uring/io_uring.c:3212
 io_uring_files_cancel include/linux/io_uring.h:19 [inline]
 do_exit+0x2ce/0x2bd0 kernel/exit.c:911
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
 __do_sys_exit_group kernel/exit.c:1116 [inline]
 __se_sys_exit_group kernel/exit.c:1114 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1114
 x64_sys_call+0x1530/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f141ec08e39
RSP: 002b:00007ffcd1b0b6e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f141ec08e39
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 00007f141ec843b0 R08: ffffffffffffffb8 R09: 0000000000000000
R10: 000000000000000e R11: 0000000000000246 R12: 00007f141ec843b0
R13: 0000000000000000 R14: 00007f141ec880c0 R15: 00007f141ebd7020
 </TASK>
INFO: task syz-executor971:5853 blocked for more than 144 seconds.
      Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
      Blocked by coredump.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor971 state:D stack:27080 pid:5853  tgid:5853  ppid:5847   task_flags:0x400148 flags:0x00024002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5397 [inline]
 __schedule+0x116a/0x5de0 kernel/sched/core.c:6786
 __schedule_loop kernel/sched/core.c:6864 [inline]
 schedule+0xe7/0x3a0 kernel/sched/core.c:6879
 schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
 do_wait_for_common kernel/sched/completion.c:95 [inline]
 __wait_for_common+0x2ff/0x4e0 kernel/sched/completion.c:116
 io_wq_exit_workers io_uring/io-wq.c:1319 [inline]
 io_wq_put_and_exit+0x271/0x8d0 io_uring/io-wq.c:1347
 io_uring_clean_tctx+0x10d/0x190 io_uring/tctx.c:203
 io_uring_cancel_generic+0x69c/0x9a0 io_uring/io_uring.c:3212
 io_uring_files_cancel include/linux/io_uring.h:19 [inline]
 do_exit+0x2ce/0x2bd0 kernel/exit.c:911
 do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
 __do_sys_exit_group kernel/exit.c:1116 [inline]
 __se_sys_exit_group kernel/exit.c:1114 [inline]
 __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1114
 x64_sys_call+0x1530/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f141ec08e39
RSP: 002b:00007ffcd1b0b6e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f141ec08e39
RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
RBP: 00007f141ec843b0 R08: ffffffffffffffb8 R09: 0000000000000000
R10: 000000000000000e R11: 0000000000000246 R12: 00007f141ec843b0
R13: 0000000000000000 R14: 00007f141ec880c0 R15: 00007f141ebd7020
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/31:
 #0: ffffffff8e5c4e00 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
 #0: ffffffff8e5c4e00 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
 #0: ffffffff8e5c4e00 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x36/0x1c0 kernel/locking/lockdep.c:6770
2 locks held by getty/5594:
 #0: ffff888032cc90a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc900036cb2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x41b/0x14f0 drivers/tty/n_tty.c:2222

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:307 [inline]
 watchdog+0xf70/0x12c0 kernel/hung_task.c:470
 kthread+0x3c5/0x780 kernel/kthread.c:464
 ret_from_fork+0x5d4/0x6f0 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:82
Code: 7b 6d 02 e9 83 fb 02 00 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 43 99 23 00 fb f4 <c3> cc cc cc cc 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffffff8e207e08 EFLAGS: 000002c6
RAX: 00000000000d6725 RBX: 0000000000000000 RCX: ffffffff8b867c99
RDX: 0000000000000000 RSI: ffffffff8de2fff6 RDI: ffffffff8c157460
RBP: fffffbfff1c52ef0 R08: 0000000000000001 R09: ffffed1017086645
R10: ffff8880b843322b R11: 0000000000000001 R12: 0000000000000000
R13: ffffffff8e297780 R14: ffffffff90a94550 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff888124720000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055e50c02d168 CR3: 000000000e382000 CR4: 00000000003526f0
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:107 [inline]
 default_idle+0x13/0x20 arch/x86/kernel/process.c:749
 default_idle_call+0x6d/0xb0 kernel/sched/idle.c:117
 cpuidle_idle_call kernel/sched/idle.c:185 [inline]
 do_idle+0x391/0x510 kernel/sched/idle.c:325
 cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:423
 rest_init+0x16b/0x2b0 init/main.c:745
 start_kernel+0x3ee/0x4d0 init/main.c:1102
 x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:307
 x86_64_start_kernel+0x130/0x190 arch/x86/kernel/head64.c:288
 common_startup_64+0x13e/0x148
 </TASK>


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
For information about bisection process see: https://goo.gl/tpsmEJ#bisection

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

Re: [syzbot] [input?] [usb?] [io-uring?] INFO: task hung in io_wq_put_and_exit (5)

[Jens Axboe]

On Wed, Jul 23, 2025 at 8:44?AM syzbot <syzbot+e328767eafd849df0a78@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    bf61759db409 Merge tag 'sched_ext-for-6.16-rc6-fixes' of g..
> git tree:       upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=12b877d4580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=415e83411fefd73f
> dashboard link: https://syzkaller.appspot.com/bug?extid=e328767eafd849df0a78
> compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=110b938c580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1622a38c580000
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/22c5f1286a72/disk-bf61759d.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cc79af4d966c/vmlinux-bf61759d.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/b2e6d621f424/bzImage-bf61759d.xz
>
> The issue was bisected to:
>
> commit e5598d6ae62626d261b046a2f19347c38681ff51
> Author: Pavel Begunkov <asml.silence@gmail.com>
> Date:   Thu Aug 24 22:53:31 2023 +0000
>
>     io_uring: compact SQ/CQ heads/tails
>
> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12c92b82580000
> final oops:     https://syzkaller.appspot.com/x/report.txt?x=11c92b82580000
> console output: https://syzkaller.appspot.com/x/log.txt?x=16c92b82580000
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+e328767eafd849df0a78@syzkaller.appspotmail.com
> Fixes: e5598d6ae626 ("io_uring: compact SQ/CQ heads/tails")
>
> INFO: task syz-executor971:5849 blocked for more than 143 seconds.
>       Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
>       Blocked by coredump.
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:syz-executor971 state:D stack:26488 pid:5849  tgid:5849  ppid:5844   task_flags:0x400148 flags:0x00024002
> Call Trace:
>  <TASK>
>  context_switch kernel/sched/core.c:5397 [inline]
>  __schedule+0x116a/0x5de0 kernel/sched/core.c:6786
>  __schedule_loop kernel/sched/core.c:6864 [inline]
>  schedule+0xe7/0x3a0 kernel/sched/core.c:6879
>  schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
>  do_wait_for_common kernel/sched/completion.c:95 [inline]
>  __wait_for_common+0x2ff/0x4e0 kernel/sched/completion.c:116
>  io_wq_exit_workers io_uring/io-wq.c:1319 [inline]
>  io_wq_put_and_exit+0x271/0x8d0 io_uring/io-wq.c:1347
>  io_uring_clean_tctx+0x10d/0x190 io_uring/tctx.c:203
>  io_uring_cancel_generic+0x69c/0x9a0 io_uring/io_uring.c:3212
>  io_uring_files_cancel include/linux/io_uring.h:19 [inline]
>  do_exit+0x2ce/0x2bd0 kernel/exit.c:911
>  do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
>  __do_sys_exit_group kernel/exit.c:1116 [inline]
>  __se_sys_exit_group kernel/exit.c:1114 [inline]
>  __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1114
>  x64_sys_call+0x1530/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
>  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
>  do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f141ec08e39
> RSP: 002b:00007ffcd1b0b6e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f141ec08e39
> RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> RBP: 00007f141ec843b0 R08: ffffffffffffffb8 R09: 0000000000000000
> R10: 000000000000000e R11: 0000000000000246 R12: 00007f141ec843b0
> R13: 0000000000000000 R14: 00007f141ec880c0 R15: 00007f141ebd7020
>  </TASK>
> INFO: task syz-executor971:5850 blocked for more than 143 seconds.
>       Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
>       Blocked by coredump.

I took a look at this one, and it's simply waiting on nullb0 timeouts
that it's flooded the queue with. Since it's flooding the nullb0 device
which has been configured to time out IO, we'll have a lot of io-wq
workers that are sitting blocked waiting on making progress. That can
obviously take a long time, which then in turn triggers the io_uring
cancelation/exit warning because of that. It all seems to be working as
it should.

I don't think there's a bug here because of that, the only thing that's
"stuck" is because each timeout takes 30s to trigger and there are tons
of them.

#syz invalid

-- 
Jens Axboe

Re: [syzbot] [input?] [usb?] [io-uring?] INFO: task hung in io_wq_put_and_exit (5)

[Aleksandr Nogikh]

Hi Jens,

On Wed, Aug 13, 2025 at 4:32 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> On Wed, Jul 23, 2025 at 8:44?AM syzbot <syzbot+e328767eafd849df0a78@syzkaller.appspotmail.com> wrote:
> >
> > Hello,
> >
> > syzbot found the following issue on:
> >
> > HEAD commit:    bf61759db409 Merge tag 'sched_ext-for-6.16-rc6-fixes' of g..
> > git tree:       upstream
> > console+strace: https://syzkaller.appspot.com/x/log.txt?x=12b877d4580000
> > kernel config:  https://syzkaller.appspot.com/x/.config?x=415e83411fefd73f
> > dashboard link: https://syzkaller.appspot.com/bug?extid=e328767eafd849df0a78
> > compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> > syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=110b938c580000
> > C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1622a38c580000
> >
> > Downloadable assets:
> > disk image: https://storage.googleapis.com/syzbot-assets/22c5f1286a72/disk-bf61759d.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/cc79af4d966c/vmlinux-bf61759d.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/b2e6d621f424/bzImage-bf61759d.xz
> >
> > The issue was bisected to:
> >
> > commit e5598d6ae62626d261b046a2f19347c38681ff51
> > Author: Pavel Begunkov <asml.silence@gmail.com>
> > Date:   Thu Aug 24 22:53:31 2023 +0000
> >
> >     io_uring: compact SQ/CQ heads/tails
> >
> > bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12c92b82580000
> > final oops:     https://syzkaller.appspot.com/x/report.txt?x=11c92b82580000
> > console output: https://syzkaller.appspot.com/x/log.txt?x=16c92b82580000
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the commit:
> > Reported-by: syzbot+e328767eafd849df0a78@syzkaller.appspotmail.com
> > Fixes: e5598d6ae626 ("io_uring: compact SQ/CQ heads/tails")
> >
> > INFO: task syz-executor971:5849 blocked for more than 143 seconds.
> >       Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
> >       Blocked by coredump.
> > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> > task:syz-executor971 state:D stack:26488 pid:5849  tgid:5849  ppid:5844   task_flags:0x400148 flags:0x00024002
> > Call Trace:
> >  <TASK>
> >  context_switch kernel/sched/core.c:5397 [inline]
> >  __schedule+0x116a/0x5de0 kernel/sched/core.c:6786
> >  __schedule_loop kernel/sched/core.c:6864 [inline]
> >  schedule+0xe7/0x3a0 kernel/sched/core.c:6879
> >  schedule_timeout+0x257/0x290 kernel/time/sleep_timeout.c:75
> >  do_wait_for_common kernel/sched/completion.c:95 [inline]
> >  __wait_for_common+0x2ff/0x4e0 kernel/sched/completion.c:116
> >  io_wq_exit_workers io_uring/io-wq.c:1319 [inline]
> >  io_wq_put_and_exit+0x271/0x8d0 io_uring/io-wq.c:1347
> >  io_uring_clean_tctx+0x10d/0x190 io_uring/tctx.c:203
> >  io_uring_cancel_generic+0x69c/0x9a0 io_uring/io_uring.c:3212
> >  io_uring_files_cancel include/linux/io_uring.h:19 [inline]
> >  do_exit+0x2ce/0x2bd0 kernel/exit.c:911
> >  do_group_exit+0xd3/0x2a0 kernel/exit.c:1105
> >  __do_sys_exit_group kernel/exit.c:1116 [inline]
> >  __se_sys_exit_group kernel/exit.c:1114 [inline]
> >  __x64_sys_exit_group+0x3e/0x50 kernel/exit.c:1114
> >  x64_sys_call+0x1530/0x1730 arch/x86/include/generated/asm/syscalls_64.h:232
> >  do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
> >  do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
> >  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7f141ec08e39
> > RSP: 002b:00007ffcd1b0b6e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
> > RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f141ec08e39
> > RDX: 000000000000003c RSI: 00000000000000e7 RDI: 0000000000000000
> > RBP: 00007f141ec843b0 R08: ffffffffffffffb8 R09: 0000000000000000
> > R10: 000000000000000e R11: 0000000000000246 R12: 00007f141ec843b0
> > R13: 0000000000000000 R14: 00007f141ec880c0 R15: 00007f141ebd7020
> >  </TASK>
> > INFO: task syz-executor971:5850 blocked for more than 143 seconds.
> >       Not tainted 6.16.0-rc6-syzkaller-00279-gbf61759db409 #0
> >       Blocked by coredump.
>
> I took a look at this one, and it's simply waiting on nullb0 timeouts
> that it's flooded the queue with. Since it's flooding the nullb0 device
> which has been configured to time out IO, we'll have a lot of io-wq
> workers that are sitting blocked waiting on making progress. That can
> obviously take a long time, which then in turn triggers the io_uring
> cancelation/exit warning because of that. It all seems to be working as
> it should.
>
> I don't think there's a bug here because of that, the only thing that's
> "stuck" is because each timeout takes 30s to trigger and there are tons
> of them.
>
> #syz invalid

FWIW: if the bug is weird, but syzbot keeps on observing the crashes,
it's better to let it stay open than to close it with "syz invalid".
In this case, syzbot will just reopen the bug as "INFO: task hung in
io_wq_put_and_exit (6)", "INFO: task hung in io_wq_put_and_exit (7)",
and so on.

-- 
Aleksandr

>
> --
> Jens Axboe
>