Bug 156726

Summary:	[snd_uaudio]: snd_uaudio(4) fails to detach when mixer is open
Product:	Base System	Reporter:	Arnaud <lacombar>
Component:	usb	Assignee:	freebsd-usb (Nobody) <usb>
Status:	Closed Feedback Timeout
Severity:	Affects Only Me	CC:	kevinz5000, miwi
Priority:	Normal
Version:	8.2-STABLE
Hardware:	Any
OS:	Any

Description Arnaud 2011-04-29 21:30:12 UTC

When a userland application has an open file descriptor to /dev/pcmN,
backed by an snd_uaudio(4) based device, trying to detach this device
will hang the USB stack until the userland application is closed.
Ultimately, this could lead to a complete stall of the USB stack.

It would be expected that every child of snd_uaudio(4) just detach
themselves, letting the userland die with EIO.

How-To-Repeat: plug a snd_uaudio adapter
open aumix(1)
unplug the adapter

Comment 1 Mark Linimon freebsd_committer

2011-05-02 01:24:11 UTC

Responsible Changed
From-To: freebsd-amd64->freebsd-multimedia

reclassify.

Comment 2 Gavin Atkinson freebsd_committer

2012-08-16 13:53:15 UTC

Responsible Changed
From-To: freebsd-multimedia->freebsd-usb

This sounds potentially like a USB stack issue to me.

Comment 3 Hans Petter Selasky 2012-08-16 19:22:40 UTC

On Thursday 16 August 2012 14:54:00 gavin@freebsd.org wrote:
> Synopsis: [snd_uaudio]: snd_uaudio(4) fails to detach when mixer is open
> 
> Responsible-Changed-From-To: freebsd-multimedia->freebsd-usb
> Responsible-Changed-By: gavin
> Responsible-Changed-When: Thu Aug 16 12:53:15 UTC 2012
> Responsible-Changed-Why:
> This sounds potentially like a USB stack issue to me.
> 
> http://www.freebsd.org/cgi/query-pr.cgi?pr=156726

This is not a USB stack problem, but a sound system issue.

This is a known issue.

--HPS

Comment 4 Kevin Zheng 2021-10-17 18:15:01 UTC

I ran into this problem in 13.0-RELEASE. In my case, suspend (via acpiconf) hangs on uaudio_detach_sub() ("Waiting for sound application to exit!") because an application is holding the mixer open. Can we re-open this issue for investigating a fix on the sound side, or should I open a new PR?

Comment 5 Kevin Zheng 2021-10-17 18:16:42 UTC

(In reply to Kevin Zheng from comment #4)
Looks like this duplicates 194727. Could someone with permissions please add this to the duplicates list?