Heisenbug. Surely ;-)
Okay, I had similar problem in assembly, but that was probably
hardware... I included a single NOP instruction which solved a lot of
problems in a MCU by moving the rest of the program one instruction
away. But one thing the disabled debug messages surely do is that it
speeds up the program a bit and potantially makes it much more
responsive due to cache size - when there is no debug, it cannot
possibly take the valuable CPU cache.
On 5/1/07, Jon Elson <[EMAIL PROTECTED]> wrote:
> Well, I was afraid of this - maybe this is another strong
> indication of a software cause for my problem with the ppmc
> driver. I uncommented 3 kernel message writes in the encoder
> section of the driver (enabling index reset, clearing it when
> the index pulse is seen, and cancelling it if somebody else
> were to clear the hal signal.) Well, I ran it for an hour
> without a single bobble! Hmmm, now that I think about it, I
> probably had those debug writes active during all my testing,
> and turned them off before one final test and then committed the
> driver changes. Sheesh, I used to have to track down junk like
> this in people's Fortran programs where they had mismatched
> array sizes in common blocks. I was hoping that was a bad memory!
>
> So, is this the typical mess where things get moved around in
> memory when you put in debugging statements and that fixes the
> problem? Or is it a timing change due to the added kernel
> writes? These rtapi_print_msg commands are only executed on a
> change of state of the index-en pin, so there are 2 messages for
> every threading pass.
>
> Or, is it the convoluted if-thens that are somehow being changed
> by the print statements? That doesn't seem likely, as they are
> just another statement between { } braces.
>
> I'll have to comment those lines back out and see if the
> procedure fails like it did at the show.
>
> Jon
>
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