Andrea wrote:
> I've been playing with DMX_SET_BUFFER_SIZE and I've had a problem when I tried to resize the buffer
> to a smaller size.
>
> dvb_dmxdev_set_buffer_size flushes the ringbuffer and then replaces it with a new one.
> What happens if the current pointer is on a position that would be invalid in the new buffer? An
> access violation.
>
> This because dvb_ringbuffer_flush resets the 2 pointers to the vaule of pwrite (which could be after
> the end of the new buffer).
Ack, this _is_ a bug. :-(
> I think it is safer to reset them to 0.
Nak. At the first glance one might think that this patch is correct.
Unfortunately, it introduces a subtle bug.
Citing the comments in dvb_ringbuffer.h:
| (2) If there is exactly one reader and one writer, there is no need
| to lock read or write operations.
| Two or more readers must be locked against each other.
| Flushing the buffer counts as a read operation.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
| Two or more writers must be locked against each other.
With your patch all dvb_ringbuffer_flush() calls must also be considered
as write operations. As a consequence, you would have to add spinlock
protection at many places in the code...
So I suggest to leave dvb_ringbuffer_flush() as is and zero the read and
write pointers only where it is really required...
CU
Oliver
--
----------------------------------------------------------------
VDR Remote Plugin 0.4.0: http://www.escape-edv.de/endriss/vdr/
----------------------------------------------------------------
_______________________________________________
linux-dvb mailing list
linux-dvb@xxxxxxxxxxx
http://www.linuxtv.org/cgi-bin/mailman/listinfo/linux-dvb
