Ken,
I believe that your assumption about the buffer not being contiguous is correct.
Therefore, you should let the task run past the end of the buffer. If you want to
keep this functionality without too much effort you could revert the old method of
allocating shared memory by reserving it at boot up through lilo. This memory is
contiguous.
I hope this helps,
Rich
> ----------
> From: Ken Teh[SMTP:[EMAIL PROTECTED]]
> Reply To: [EMAIL PROTECTED]
> Sent: Tuesday, April 10, 2001 1:59 PM
> To: Real Time Linux
> Subject: [rtl] paging problem with RTL-3.0
>
> It appears that I cannot page when running my rt code. RTLinux is version
> 3.0
>
> I have a statically defined buffer that is partitioned into n+2 buffers, each
> 2048 bytes long and a function that fills these buffers with multiple
> blocks of "event" data. The function writes arbitrary length event data and
> I allow the function to overrun a buffer boundary. The calling function
> actually catches the overrun and translates (shifts) the "last" event into
> the next buffer so that the completed buffer does not contain partial event
> data.
>
> The system does an oops when the function overflows from buffer 1 (first
> buffer is buffer 0) into buffer 2. At times it's worse -- it resets the
> computer and goes into the reboot cycle. If I fix the function so it never
> overruns a buffer boundary, then the code runs without any problems.
>
> The n buffers are actually made into a circular buffer queue. The n+1
> buffer is used for the overflow of buffer n, and the n+2 buffer is the
> temporary buffer which I use to translate an event data block that has
> overrun a buffer boundary. I've checked that with my modified function
> (that does not overrun a buffer boundary), that the buffers "circulate"
> without any problems.
>
> My inference is that my logically contiguous buffer that is partitioned into
> n+2 buffers is not really physically contiguous and that when my function
> overflows buffer 1, ie, crosses a page boundary, the system does a hard
> crash. I have the same behaviour with the mbuff device. The function is
> called by a thread that is dispatched by an interrupt handler.
>
> Can anyone shed light on this?
>
> The oops message repeats, but I don't know how to read an oops and I've seen
> 2 varieties of oops messages - one says kernel cannot deference NULL virtual
> pointer, process is init, the second variety says something about trying to
> kill an interrupt handler, aiee killing idle task. I'm not sure I believe
> either one.
>
> Ken
>
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