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Lou Sortman <lou_sortman@servicemerchandise.com> wrote:
> > Alternatively, you could just change tm_switcher() to ignore tasks that are
> > in a 'P_SUSPENDED' state or something like that.
> The simplicity of that approach could well be worth the trivial drop in performance
> vs the separate queue approach.
It's what I'm doing for now in my debugger work. I haven't tried it out
yet, though.
> > > I'll be interested in seeing if you can make breakpoints work. I can't think
> > > of an easy way with the available hardware.
> >
> > The best I could come up with was to overwrite the instruction with a jump
> > to itself, and when the scheduler reschedules a task, it would check if it
> > was stopped on this instruction; and if it was it would tell the denugger.
> On this architecture, are all instructions the same length as the mentioned jump (or
> longer)? (I don't have the manual handy.) If so, this does seem like a good way
> to do it. The scheduler could dereference the stack pointer and see if it points to
> (or just past) that opcode, and only (take the time to) scan the breakpoint list if
> it does. I am assuming that a jump to one's own address is going to be a relative
> jump, and, therefore, always the same byte sequence.
I carefully looked at the opcodes, and found that the shortest opcodes are
all 2 bytes, and hand-coded the 2 byte instruction that jumps to itself.
The scheduler can do exactly as you said, and actually I was thinking that
it would just suspend the task and somehow notify the debug task, who
would be responsible for scanning the breakpoint list. Yes, it is a
relative jump.
-Matt
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Message is in Reply To:
 | | Re: Debugging
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| (...) However, last night, I wrote a brute force (spin loop) msleep which works fine in the scheduler. I found that 800 iterations of an empty for loop with a 16 bit index comes pretty close to 1ms. Granted, I cheated a little, knowing that the (...) (28 years ago, 17-Mar-99, to lugnet.robotics.rcx.legos)
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