[syzbot] usb-testing boot error: INFO: task hung in add_early_randomness

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: f2906aa86338 Linux 5.19-rc1
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=1042a03bf00000
kernel config: https://syzkaller.appspot.com/x/.config?x=3bafeb86189666d4
dashboard link: https://syzkaller.appspot.com/bug?extid=695f4009c37860232f35
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+695f40...@syzkaller.appspotmail.com

INFO: task swapper/0:1 blocked for more than 143 seconds.
Not tainted 5.19.0-rc1-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:swapper/0 state:D stack:23984 pid: 1 ppid: 0 flags:0x00004000
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5116 [inline]
__schedule+0x93c/0x25e0 kernel/sched/core.c:6428
schedule+0xd2/0x1f0 kernel/sched/core.c:6500
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6559
__mutex_lock_common kernel/locking/mutex.c:679 [inline]
__mutex_lock+0xa70/0x1350 kernel/locking/mutex.c:747
add_early_randomness+0x1a/0x170 drivers/char/hw_random/core.c:69
hwrng_register+0x399/0x510 drivers/char/hw_random/core.c:599
virtrng_scan+0x37/0x90 drivers/char/hw_random/virtio-rng.c:205
virtio_dev_probe+0x639/0x910 drivers/virtio/virtio.c:313
call_driver_probe drivers/base/dd.c:555 [inline]
really_probe+0x23e/0xb90 drivers/base/dd.c:634
__driver_probe_device+0x338/0x4d0 drivers/base/dd.c:764
driver_probe_device+0x4c/0x1a0 drivers/base/dd.c:794
__driver_attach+0x22d/0x550 drivers/base/dd.c:1163
bus_for_each_dev+0x147/0x1d0 drivers/base/bus.c:301
bus_add_driver+0x422/0x640 drivers/base/bus.c:618
driver_register+0x220/0x3a0 drivers/base/driver.c:240
do_one_initcall+0x103/0x650 init/main.c:1295
do_initcall_level init/main.c:1368 [inline]
do_initcalls init/main.c:1384 [inline]
do_basic_setup init/main.c:1403 [inline]
kernel_init_freeable+0x6ac/0x735 init/main.c:1610
kernel_init+0x1a/0x1d0 init/main.c:1499
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:302
</TASK>

Showing all locks held in the system:
2 locks held by swapper/0/1:
#0: ffff88810cb9e170 (&dev->mutex){....}-{3:3}, at: device_lock include/linux/device.h:835 [inline]
#0: ffff88810cb9e170 (&dev->mutex){....}-{3:3}, at: __device_driver_lock drivers/base/dd.c:1054 [inline]
#0: ffff88810cb9e170 (&dev->mutex){....}-{3:3}, at: __driver_attach+0x222/0x550 drivers/base/dd.c:1162
#1: ffffffff87edbbe8 (reading_mutex){+.+.}-{3:3}, at: add_early_randomness+0x1a/0x170 drivers/char/hw_random/core.c:69
2 locks held by pr/ttyS0/14:
1 lock held by khungtaskd/27:
#0: ffffffff87a94840 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x53/0x260 kernel/locking/lockdep.c:6491
1 lock held by hwrng/150:
#0: ffffffff87edbbe8 (reading_mutex){+.+.}-{3:3}, at: hwrng_fillfn+0x141/0x370 drivers/char/hw_random/core.c:503

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



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[Dmitry Vyukov]

On Tue, 7 Jun 2022 at 08:33, syzbot
<syzbot+695f40...@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: f2906aa86338 Linux 5.19-rc1
> 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=1042a03bf00000
> kernel config: https://syzkaller.appspot.com/x/.config?x=3bafeb86189666d4
> dashboard link: https://syzkaller.appspot.com/bug?extid=695f4009c37860232f35
> compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+695f40...@syzkaller.appspotmail.com

Assume this is also fixed by:

#syz fix: virtio-rng: make device ready before making request

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