uaudio: pulseaudio locks up system

[Hans Petter Selasky]

On 2/14/21 2:17 PM, Stefan Ehmann wrote:
> Rebuilt kernel with debug options. I see this LOR when running pactl list:
> 
> lock order reversal:
>   1st 0xfffff80005cc3840 pcm7:play:dsp7.p0 (pcm play channel, sleep mutex) @ /
> usr/src/sys/dev/usb/usb_transfer.c:2342
>   2nd 0xfffff80005cc3860 pcm7:record:dsp7.r0 (pcm record channel, sleep mutex)
> @ /usr/src/sys/dev/sound/usb/uaudio.c:2317
> lock order pcm record channel -> pcm play channel established at:
> #0 0xffffffff80714e91 at witness_checkorder+0x461
> #1 0xffffffff80684878 at __mtx_lock_flags+0x98
> #2 0xffffffff804dc721 at dsp_mmap_single+0x151
> #3 0xffffffff8096b995 at vm_mmap_cdev+0x65
> #4 0xffffffff805500e3 at devfs_mmap_f+0x143
> #5 0xffffffff80969fb4 at kern_mmap_req+0x594
> #6 0xffffffff80969996 at sys_mmap+0x46
> #7 0xffffffff80a0ecce at amd64_syscall+0x12e
> #8 0xffffffff809e4a7e at fast_syscall_common+0xf8
> lock order pcm play channel -> pcm record channel attempted at:
> #0 0xffffffff807157b2 at witness_checkorder+0xd82
> #1 0xffffffff80684878 at __mtx_lock_flags+0x98
> #2 0xffffffff844ad2eb at uaudio_chan_play_callback+0xeb
> #3 0xffffffff8053586c at usbd_callback_wrapper+0x7ec
> #4 0xffffffff80536bbe at usb_command_wrapper+0x7e
> #5 0xffffffff805359ee at usb_callback_proc+0x8e
> #6 0xffffffff80530883 at usb_process+0xf3
> #7 0xffffffff806628a0 at fork_exit+0x80
> #8 0xffffffff809e51de at fork_trampoline+0xe

Hi,

I see the issue and will fix it and thank you for the backtrace. 
Meanwhile I believe if you disable mmap for the OSS pulseaudio backend 
this issue will disappear.

--HPS