[linux-dvb] Re: Poll problem with multiple PIDs

[Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de>]

Johannes Stezenbach wrote:
> 
> On Mon, Jun 17, 2002 at 11:18:53PM +0200, Klaus Schmidinger wrote:
> > --- dmxdev.c    Mon Apr  1 10:59:46 2002
> > +++ dmxdev.c    Sun Jun 16 11:02:38 2002
> > @@ -1048,6 +1048,9 @@
> >                 if (dmxdev->dvr_buffer.pread!=dmxdev->dvr_buffer.pwrite)
> >                         return (POLLIN | POLLRDNORM | POLLPRI);
> >
> > +                if (dmxdev->dvr_buffer.error)
> > +                       return (POLLIN | POLLRDNORM | POLLPRI | POLLERR);
> > +
> >                 return 0;
> >         } else
> >                 return (POLLOUT | POLLWRNORM | POLLPRI);
> >
> > Apparently it also has been adopted in the CVS driver today.
> 
> While this code looks right, your error handling in x2.c is incomplete,
> since you don't check the result code / errno of read().

x2.c was just a little example to demonstrate the bug in the driver.
The fact is that in case of a buffer overflow the driver got into
a state where any further poll() calls did not return POLLIN any more.

Of course I do check the return value of read() in VDR ;-)

Klaus
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Klaus Schmidinger                       Phone: +49-8635-6989-10
CadSoft Computer GmbH                   Fax:   +49-8635-6989-40
Hofmark 2                               Email:   kls@cadsoft.de
D-84568 Pleiskirchen, Germany           URL:     www.cadsoft.de
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