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    SubjectRe: [linux-usb-devel] USB snd-usb-audio wedges lsusb when unplugged while playing sound.
    On 7/22/06, Ian Stirling <> 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.

    It boils down to this: although the low-level usb code is properly
    reporting and distinguishing error conditions, usb-audio translates
    just about everything that goes wrong into 'EPIPE'. Because an
    application has no way to distinguish temporary from permanent errors
    (and the coding docs specify that the app resubmit), it immediately
    retries and gets another EPIPE. This infinite retry loop places
    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.

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      Last update: 2006-07-22 18:51    [W:0.021 / U:38.872 seconds]
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