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    Subject[127/197] Staging: comedi: usbdux.c: fix locking up of the driver when the comedi ringbuffer runs empty
    2.6.32-stable review patch.  If anyone has any objections, please let us know.

    ------------------

    From: Bernd Porr <berndporr@f2s.com>

    commit d4c3a56587af3edbe5f618b20e800e9f9fde13cb upstream.

    Jan-Matthias Braun spotted a bug which locks up the driver when the
    comedi ring buffer runs empty and provided a patch. The driver would
    still send the data to comedi but the reader won't wake up any more.
    What's required is setting the flag COMEDI_CB_BLOCK after new data has
    arrived which wakes up the reader and therefore the read() command.

    Signed-off-by: Bernd Porr <berndporr@f2s.com>
    Signed-off-by: Leann Ogasawara <leann.ogasawara@canonical.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/staging/comedi/drivers/usbdux.c | 5 ++++-
    1 file changed, 4 insertions(+), 1 deletion(-)

    --- a/drivers/staging/comedi/drivers/usbdux.c
    +++ b/drivers/staging/comedi/drivers/usbdux.c
    @@ -1,4 +1,4 @@
    -#define DRIVER_VERSION "v2.3"
    +#define DRIVER_VERSION "v2.4"
    #define DRIVER_AUTHOR "Bernd Porr, BerndPorr@f2s.com"
    #define DRIVER_DESC "Stirling/ITL USB-DUX -- Bernd.Porr@f2s.com"
    /*
    @@ -81,6 +81,8 @@ sampling rate. If you sample two channel
    * 2.1: changed PWM API
    * 2.2: added firmware kernel request to fix an udev problem
    * 2.3: corrected a bug in bulk timeouts which were far too short
    + * 2.4: fixed a bug which causes the driver to hang when it ran out of data.
    + * Thanks to Jan-Matthias Braun and Ian to spot the bug and fix it.
    *
    */

    @@ -532,6 +534,7 @@ static void usbduxsub_ai_IsocIrq(struct
    }
    }
    /* tell comedi that data is there */
    + s->async->events |= COMEDI_CB_BLOCK | COMEDI_CB_EOS;
    comedi_event(this_usbduxsub->comedidev, s);
    }




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