Re: [linux-usb-devel] USB snd-usb-audio wedges lsusb when unplugged while playing sound.

[Ian Stirling <tandra@mauve.plus.com>]

Christopher Montgomery wrote:
> On 7/22/06, Ian Stirling <tandra@mauve.plus.com> wrote:
> 
>> Config/... as my earlier message on USB - though with the bandwidth
>> enforcement
>> turned off so it actually plays sound, when plugged into the USB1 port.
>>
>> 2.6.17.
>>
>> Basically - playing sound with
>> mplayer -ao alsa:device=hw=1 or whatever - and then unplugging the
>> soundcard completely wedges lsusb/usb configuration, until the mplayer
>> process is killed.
> 
> 
> This sounds like the well known EPIPE problem in usb-audio and one I
> intended to fix after dealing with the ehci scheduler.
<snip>
> enough system load on the machine that it may well even stop pinging.
> Although the *machine* is not wedged, if this happens in a realtime
> thread (eg, jack using a usb-audio device), it may well be hosed
> enough to become unrecoverable.

I just did it again, and the machine is >90% idle (PII/300), with 
mplayer doing:

ioctl(5, 0x806c4120, 0xbffeffd0)        = -1 ENODEV (No such device)
write(2, "alsa-lib: pcm_hw.c:406:(snd_pcm_"..., 89) = 89
write(2, "alsa-space: cannot get pcm statu"..., 50) = 50
nanosleep({0, 10000000}, NULL)          = 0
ioctl(5, 0x806c4120, 0xbffeffd0)        = -1 ENODEV (No such device)

about 70 times a second.
Of course, with other software, it may be different.