INFO: task hung in __do_sys_reboot

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: b3a5ce87 usb: cdns3: gadget: Replace trace_printk by dev_dbg
git tree: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing
console output: https://syzkaller.appspot.com/x/log.txt?x=16916b55100000
kernel config: https://syzkaller.appspot.com/x/.config?x=63b40b2ae167bad6
dashboard link: https://syzkaller.appspot.com/bug?extid=7479735e20e43cf78563
compiler: gcc (GCC) 10.1.0-syz 20200507
CC: [gre...@linuxfoundation.org linux-...@vger.kernel.org raf...@kernel.org linu...@vger.kernel.org]

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+747973...@syzkaller.appspotmail.com

INFO: task systemd-shutdow:1 blocked for more than 143 seconds.
Not tainted 5.8.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
systemd-shutdow D24504 1 0 0x00004000
Call Trace:
context_switch kernel/sched/core.c:3430 [inline]
__schedule+0x88a/0x1cb0 kernel/sched/core.c:4155
schedule+0xcd/0x2b0 kernel/sched/core.c:4230
wait_for_device_probe+0x1be/0x220 drivers/base/dd.c:665
device_shutdown+0x18/0x5b5 drivers/base/core.c:3748
kernel_restart_prepare kernel/reboot.c:76 [inline]
kernel_restart kernel/reboot.c:246 [inline]
__do_sys_reboot.cold+0x5d/0x9d kernel/reboot.c:347
do_syscall_64+0x50/0x90 arch/x86/entry/common.c:359
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7f992326e8c6
Code: Bad RIP value.
RSP: 002b:00007ffc10bfbea8 EFLAGS: 00000202 ORIG_RAX: 00000000000000a9
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f992326e8c6
RDX: 0000000001234567 RSI: 0000000028121969 RDI: fffffffffee1dead
RBP: 00007ffc10bfbf38 R08: 0000000000000028 R09: 0000000000000005
R10: 0000000000000002 R11: 0000000000000202 R12: 0000000000000000
R13: 0000000000000000 R14: 0000561f5f231150 R15: 00007ffc10bfc228

Showing all locks held in the system:
1 lock held by systemd-shutdow/1:
#0: ffffffff872e6428 (system_transition_mutex){+.+.}-{3:3}, at: __do_sys_reboot+0x1a4/0x3e0 kernel/reboot.c:344
1 lock held by khungtaskd/23:
#0: ffffffff8730f960 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x264 kernel/locking/lockdep.c:5779
5 locks held by kworker/0:6/3085:

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

NMI backtrace for cpu 0
CPU: 0 PID: 23 Comm: khungtaskd Not tainted 5.8.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0xf6/0x16e lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x74/0xb6 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1da/0x1f4 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:209 [inline]
watchdog+0xd6a/0xfd0 kernel/hung_task.c:295
kthread+0x392/0x470 kernel/kthread.c:291
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt arch/x86/include/asm/irqflags.h:60 [inline]
NMI backtrace for cpu 1 skipped: idling at arch_safe_halt arch/x86/include/asm/irqflags.h:103 [inline]
NMI backtrace for cpu 1 skipped: idling at acpi_safe_halt+0x72/0x90 drivers/acpi/processor_idle.c:111


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[syzbot]

Sending this report upstream.