Re: [syzbot] [usb?] INFO: task hung in hub_activate (3)

From: Hillf Danton
Date: Wed Jul 02 2025 - 04:05:57 EST

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In reply to: syzbot: "[syzbot] [usb?] INFO: task hung in hub_activate (3)"
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On Tue, 01 Jul 2025 17:50:28 -0700
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 1343433ed389 Add linux-next specific files for 20250630
> git tree: linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=10d1f88c580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=66357ac5b0466f16
> dashboard link: https://syzkaller.appspot.com/bug?extid=d630bd89141124cc543e
> compiler: Debian clang version 20.1.6 (++20250514063057+1e4d39e07757-1~exp1~20250514183223.118), Debian LLD 20.1.6
>
> Unfortunately, I don't have any reproducer for this issue yet.
>
> Downloadable assets:
> disk image: https://storage.googleapis.com/syzbot-assets/b005e1db0f8c/disk-1343433e.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/cb3aa8bfd514/vmlinux-1343433e.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/e01227599a09/bzImage-1343433e.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+d630bd89141124cc543e@xxxxxxxxxxxxxxxxxxxxxxxxx
>
> INFO: task kworker/0:0:9 blocked for more than 143 seconds.
> Not tainted 6.16.0-rc4-next-20250630-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:kworker/0:0 state:D stack:21240 pid:9 tgid:9 ppid:2 task_flags:0x4208060 flags:0x00004000
> Workqueue: events_power_efficient hub_init_func2
> Call Trace:
> <TASK>
> context_switch kernel/sched/core.c:5313 [inline]
> __schedule+0x16f5/0x4d00 kernel/sched/core.c:6696
> __schedule_loop kernel/sched/core.c:6774 [inline]
> schedule+0x165/0x360 kernel/sched/core.c:6789
> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6846
> __mutex_lock_common kernel/locking/mutex.c:679 [inline]
> __mutex_lock+0x724/0xe80 kernel/locking/mutex.c:747
> device_lock include/linux/device.h:884 [inline]
> hub_activate+0xb7/0x1ea0 drivers/usb/core/hub.c:1096
> process_one_work kernel/workqueue.c:3239 [inline]
> process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3322
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3403
> kthread+0x70e/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>

Due to lockdep_set_novalidate_class(&dev->mutex) in device_initialize(),
task hung instead of deadlock is reported once more.

kworker/0:0:9 kworker/0:5:5923
--- ---
hub_init_func2() usb_disconnect()
device_lock()
device_lock() hub_disconnect()
hub_quiesce()
flush_delayed_work(&hub->init_work);
*** DEADLOCK ***

> INFO: task kworker/1:0:24 blocked for more than 143 seconds.
> Not tainted 6.16.0-rc4-next-20250630-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:kworker/1:0 state:D stack:22792 pid:24 tgid:24 ppid:2 task_flags:0x4288060 flags:0x00004000
> Workqueue: usb_hub_wq hub_event
> Call Trace:
> <TASK>
> context_switch kernel/sched/core.c:5313 [inline]
> __schedule+0x16f5/0x4d00 kernel/sched/core.c:6696
> __schedule_loop kernel/sched/core.c:6774 [inline]
> schedule+0x165/0x360 kernel/sched/core.c:6789
> schedule_timeout+0x9a/0x270 kernel/time/sleep_timeout.c:75
> do_wait_for_common kernel/sched/completion.c:100 [inline]
> __wait_for_common kernel/sched/completion.c:121 [inline]
> wait_for_common kernel/sched/completion.c:132 [inline]
> wait_for_completion+0x2bf/0x5d0 kernel/sched/completion.c:153
> __flush_work+0x9b9/0xbc0 kernel/workqueue.c:4247
> flush_work kernel/workqueue.c:4268 [inline]
> flush_delayed_work+0x13e/0x190 kernel/workqueue.c:4290
> hub_quiesce+0x1f0/0x330 drivers/usb/core/hub.c:1421
> hub_disconnect+0xc8/0x470 drivers/usb/core/hub.c:1821
> usb_unbind_interface+0x26b/0x910 drivers/usb/core/driver.c:458
> device_remove drivers/base/dd.c:569 [inline]
> __device_release_driver drivers/base/dd.c:1272 [inline]
> device_release_driver_internal+0x4d6/0x7c0 drivers/base/dd.c:1295
> bus_remove_device+0x34d/0x410 drivers/base/bus.c:579
> device_del+0x511/0x8e0 drivers/base/core.c:3880
> usb_disable_device+0x3e9/0x8a0 drivers/usb/core/message.c:1418
> usb_disconnect+0x330/0x950 drivers/usb/core/hub.c:2349
> hub_port_connect drivers/usb/core/hub.c:5411 [inline]
> hub_port_connect_change drivers/usb/core/hub.c:5711 [inline]
> port_event drivers/usb/core/hub.c:5871 [inline]
> hub_event+0x1cdb/0x4a00 drivers/usb/core/hub.c:5953
> process_one_work kernel/workqueue.c:3239 [inline]
> process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3322
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3403
> kthread+0x70e/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>
> INFO: task kworker/1:4:5881 blocked for more than 144 seconds.
> Not tainted 6.16.0-rc4-next-20250630-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:kworker/1:4 state:D stack:21304 pid:5881 tgid:5881 ppid:2 task_flags:0x4208060 flags:0x00004000
> Workqueue: events_power_efficient hub_init_func2

Ditto, deadlock with kworker/1:0:24

> Call Trace:
> <TASK>
> context_switch kernel/sched/core.c:5313 [inline]
> __schedule+0x16f5/0x4d00 kernel/sched/core.c:6696
> __schedule_loop kernel/sched/core.c:6774 [inline]
> schedule+0x165/0x360 kernel/sched/core.c:6789
> schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6846
> __mutex_lock_common kernel/locking/mutex.c:679 [inline]
> __mutex_lock+0x724/0xe80 kernel/locking/mutex.c:747
> device_lock include/linux/device.h:884 [inline]
> hub_activate+0xb7/0x1ea0 drivers/usb/core/hub.c:1096
> process_one_work kernel/workqueue.c:3239 [inline]
> process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3322
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3403
> kthread+0x70e/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>
> INFO: task kworker/0:5:5923 blocked for more than 144 seconds.
> Not tainted 6.16.0-rc4-next-20250630-syzkaller #0
> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> task:kworker/0:5 state:D stack:20840 pid:5923 tgid:5923 ppid:2 task_flags:0x4288060 flags:0x00004000
> Workqueue: usb_hub_wq hub_event
> Call Trace:
> <TASK>
> context_switch kernel/sched/core.c:5313 [inline]
> __schedule+0x16f5/0x4d00 kernel/sched/core.c:6696
> __schedule_loop kernel/sched/core.c:6774 [inline]
> schedule+0x165/0x360 kernel/sched/core.c:6789
> schedule_timeout+0x9a/0x270 kernel/time/sleep_timeout.c:75
> do_wait_for_common kernel/sched/completion.c:100 [inline]
> __wait_for_common kernel/sched/completion.c:121 [inline]
> wait_for_common kernel/sched/completion.c:132 [inline]
> wait_for_completion+0x2bf/0x5d0 kernel/sched/completion.c:153
> __flush_work+0x9b9/0xbc0 kernel/workqueue.c:4247
> flush_work kernel/workqueue.c:4268 [inline]
> flush_delayed_work+0x13e/0x190 kernel/workqueue.c:4290
> hub_quiesce+0x1f0/0x330 drivers/usb/core/hub.c:1421
> hub_disconnect+0xc8/0x470 drivers/usb/core/hub.c:1821
> usb_unbind_interface+0x26b/0x910 drivers/usb/core/driver.c:458
> device_remove drivers/base/dd.c:569 [inline]
> __device_release_driver drivers/base/dd.c:1272 [inline]
> device_release_driver_internal+0x4d6/0x7c0 drivers/base/dd.c:1295
> bus_remove_device+0x34d/0x410 drivers/base/bus.c:579
> device_del+0x511/0x8e0 drivers/base/core.c:3880
> usb_disable_device+0x3e9/0x8a0 drivers/usb/core/message.c:1418
> usb_disconnect+0x330/0x950 drivers/usb/core/hub.c:2349
> hub_port_connect drivers/usb/core/hub.c:5411 [inline]
> hub_port_connect_change drivers/usb/core/hub.c:5711 [inline]
> port_event drivers/usb/core/hub.c:5871 [inline]
> hub_event+0x1cdb/0x4a00 drivers/usb/core/hub.c:5953
> process_one_work kernel/workqueue.c:3239 [inline]
> process_scheduled_works+0xae1/0x17b0 kernel/workqueue.c:3322
> worker_thread+0x8a0/0xda0 kernel/workqueue.c:3403
> kthread+0x70e/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:
> 3 locks held by kworker/0:0/9:
> #0: ffff88801a882148 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
> #0: ffff88801a882148 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3322
> #1: ffffc900000e7bc0 ((work_completion)(&(&hub->init_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3215 [inline]
> #1: ffffc900000e7bc0 ((work_completion)(&(&hub->init_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3322
> #2: ffff888023888198 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:884 [inline]
> #2: ffff888023888198 (&dev->mutex){....}-{4:4}, at: hub_activate+0xb7/0x1ea0 drivers/usb/core/hub.c:1096
> 5 locks held by kworker/1:0/24:
> #0: ffff8880216a2148 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
> #0: ffff8880216a2148 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3322
> #1: ffffc900001e7bc0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3215 [inline]
> #1: ffffc900001e7bc0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3322
> #2: ffff8880287da198 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:884 [inline]
> #2: ffff8880287da198 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4a00 drivers/usb/core/hub.c:5899
> #3: ffff888026f14198 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:884 [inline]
> #3: ffff888026f14198 (&dev->mutex){....}-{4:4}, at: usb_disconnect+0xf8/0x950 drivers/usb/core/hub.c:2340
> #4: ffff888078818160 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:884 [inline]
> #4: ffff888078818160 (&dev->mutex){....}-{4:4}, at: __device_driver_lock drivers/base/dd.c:1094 [inline]
> #4: ffff888078818160 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb6/0x7c0 drivers/base/dd.c:1292
> 1 lock held by khungtaskd/31:
> #0: ffffffff8e33bee0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:331 [inline]
> #0: ffffffff8e33bee0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:841 [inline]
> #0: ffffffff8e33bee0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6770
> 2 locks held by getty/5593:
> #0: ffff8880308ca0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
> #1: ffffc9000331b2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x43e/0x1400 drivers/tty/n_tty.c:2222
> 3 locks held by kworker/1:4/5881:
> #0: ffff88801a882148 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
> #0: ffff88801a882148 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3322
> #1: ffffc90004347bc0 ((work_completion)(&(&hub->init_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3215 [inline]
> #1: ffffc90004347bc0 ((work_completion)(&(&hub->init_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3322
> #2: ffff888026f14198 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:884 [inline]
> #2: ffff888026f14198 (&dev->mutex){....}-{4:4}, at: hub_activate+0xb7/0x1ea0 drivers/usb/core/hub.c:1096
> 5 locks held by kworker/0:5/5923:
> #0: ffff8880216a2148 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
> #0: ffff8880216a2148 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x9b4/0x17b0 kernel/workqueue.c:3322
> #1: ffffc90004587bc0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3215 [inline]
> #1: ffffc90004587bc0 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x9ef/0x17b0 kernel/workqueue.c:3322
> #2: ffff8881443e8198 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:884 [inline]
> #2: ffff8881443e8198 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4a00 drivers/usb/core/hub.c:5899
> #3: ffff888023888198 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:884 [inline]
> #3: ffff888023888198 (&dev->mutex){....}-{4:4}, at: usb_disconnect+0xf8/0x950 drivers/usb/core/hub.c:2340
> #4: ffff88807a6b6160 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:884 [inline]
> #4: ffff88807a6b6160 (&dev->mutex){....}-{4:4}, at: __device_driver_lock drivers/base/dd.c:1094 [inline]
> #4: ffff88807a6b6160 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb6/0x7c0 drivers/base/dd.c:1292
>
> =============================================
>
> NMI backtrace for cpu 1
> CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.16.0-rc4-next-20250630-syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
> 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:158 [inline]
> check_hung_uninterruptible_tasks kernel/hung_task.c:307 [inline]
> watchdog+0xfee/0x1030 kernel/hung_task.c:470
> kthread+0x70e/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 1 to CPUs 0:
> NMI backtrace for cpu 0
> CPU: 0 UID: 0 PID: 5820 Comm: syz-executor Not tainted 6.16.0-rc4-next-20250630-syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
> RIP: 0010:arch_static_branch arch/x86/include/asm/jump_label.h:36 [inline]
> RIP: 0010:native_write_msr arch/x86/include/asm/msr.h:139 [inline]
> RIP: 0010:wrmsrq arch/x86/include/asm/msr.h:199 [inline]
> RIP: 0010:native_apic_msr_write+0x39/0x50 arch/x86/include/asm/apic.h:212
> Code: 74 2a 83 ff 30 74 25 eb 10 81 ff d0 00 00 00 74 1b 81 ff e0 00 00 00 74 13 c1 ef 04 81 c7 00 08 00 00 89 f9 89 f0 31 d2 0f 30 <66> 90 c3 cc cc cc cc cc f3 0f 1e fa 89 f6 31 d2 e9 42 c9 93 03 66
> RSP: 0018:ffffc90004027af8 EFLAGS: 00000046
> RAX: 0000000000010001 RBX: ffff8880b8623900 RCX: 0000000000000838
> RDX: 0000000000000000 RSI: 0000000000010001 RDI: 0000000000000838
> RBP: 0000000000000001 R08: 0000000000000000 R09: ffffffff81ae7cae
> R10: 0000000000000003 R11: ffffffff817054a0 R12: 0000000010004b7f
> R13: dffffc0000000000 R14: 0000000000010001 R15: 0000000000000020
> FS: 000055555dbfe500(0000) GS:ffff8881259e4000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 00007f9d3dd81178 CR3: 000000007685a000 CR4: 00000000003526f0
> Call Trace:
> <TASK>
> apic_write arch/x86/include/asm/apic.h:405 [inline]
> lapic_next_event+0x11/0x20 arch/x86/kernel/apic/apic.c:416
> clockevents_program_event+0x1cc/0x360 kernel/time/clockevents.c:334
> hrtimer_start_range_ns+0xda6/0x1080 kernel/time/hrtimer.c:1330
> hrtimer_start_expires include/linux/hrtimer.h:277 [inline]
> hrtimer_sleeper_start_expires kernel/time/hrtimer.c:2023 [inline]
> do_nanosleep+0x191/0x600 kernel/time/hrtimer.c:2097
> hrtimer_nanosleep+0x169/0x360 kernel/time/hrtimer.c:2147
> __do_sys_clock_nanosleep kernel/time/posix-timers.c:1399 [inline]
> __se_sys_clock_nanosleep+0x2ee/0x380 kernel/time/posix-timers.c:1376
> 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: 0033:0x7f14d39c11a3
> Code: 1f 84 00 00 00 00 00 83 ff 03 74 7b 83 ff 02 b8 fa ff ff ff 49 89 ca 0f 44 f8 80 3d 9e 43 1c 00 00 74 14 b8 e6 00 00 00 0f 05 <f7> d8 c3 66 2e 0f 1f 84 00 00 00 00 00 48 83 ec 28 48 89 54 24 10
> RSP: 002b:00007ffc771e7aa8 EFLAGS: 00000202 ORIG_RAX: 00000000000000e6
> RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f14d39c11a3
> RDX: 00007ffc771e7ac0 RSI: 0000000000000000 RDI: 0000000000000000
> RBP: 0000000000000000 R08: 000000001cc70deb R09: 7fffffffffffffff
> R10: 0000000000000000 R11: 0000000000000202 R12: 00007ffc771e7f10
> R13: 0000000000000004 R14: 00007ffc771e7afc R15: 00007ffc771e7b90
> </TASK>
>
>
> ---
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In reply to: syzbot: "[syzbot] [usb?] INFO: task hung in hub_activate (3)"
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