I think I identified the problem, I used code extracted from:
http://www.saillard.org/linux/pwc/files/capture.c, and the code was

          total_read_bytes = 0;
          do {
                read_bytes = read(fd, buffers[0].start, buffers[0].length);
                if (read_bytes < 0)
                    switch (errno)
                        case EIO:
                        case EAGAIN:
                total_read_bytes += read_bytes;
            } while (total_read_bytes < buffers[0].length);

I changed the read() call to a v4l2_read() and used libv4l, and that
piece of code was triggering the kernel panic.

To fix it, I just removed the do..while loop. I'm still trying to
figure out what's the problem with that though.

Thanks for the reply.

On Fri, Oct 16, 2009 at 2:42 PM, Hans de Goede <hdego...@redhat.com> wrote:
> Hi,
> On 10/16/2009 12:00 AM, Pablo Baena wrote:
>> I have a program where I use libv4l's read() emulation for simplicity.
>> But with most v4l2 webcams I've tried, I get kernel panics.
>> I have pics of the message if anyone cares to see them, I don't want
>> to flood the mailing list.
>> Basically, the names I see in the kernel panic from a uvcvideo card is:
>> uvc_queue_next_buffer
>> __bad_area_no_semaphore
>> do_page_fault
>> And a lot more.
> A panic should never happen, no matter what libv4l does (as libv4l is 100%
> userspace). Please submit a bug report with as much detail as possible to
> the
> driver author.
> Regards,
> Hans

"Not possessing the gift of reflection, a dog does not know that he
does not know, and does not understand that he understands nothing;
we, on the other hand, are aware of both. If we behave otherwise, it
is from stupidity, or else from self-deception, to preserve our peace
of mind."
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