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

From: Ian Stirling
Date: Sat Jul 22 2006 - 12:59:13 EST

Christopher Montgomery wrote:
On 7/22/06, Ian Stirling <tandra@xxxxxxxxxxxxxx> wrote:

Config/... as my earlier message on USB - though with the bandwidth
turned off so it actually plays sound, when plugged into the USB1 port.


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.
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.
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