Re: frysk.rt.SteppingEngine poking at a task's blocker list?

[Tim Moore <timoore@redhat.com>]

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Andrew Cagney wrote:
> Tim, Mike,
> 
> I noticed this in frysk.rt.SteppingEngine:
> 
>   /**
>     * Unblock a task so that, from the point of view of the stepping
>     * engine, execution can continue. For now this unblocks
>     * instruction observers and code observers for breakpoints, but
>     * ultimately I (timoore) think it should unblock all blockers.
>     */
>    public boolean continueForStepping(Task task, boolean unblockStepper) {
>        if (unblockStepper) {
>            task.requestUnblock(this.steppingObserver);
>        }
>        TaskObserver[] blockers = (TaskObserver
> [])task.getBlockers().clone();
>        for (int j = 0; j < blockers.length; j++) {
>            // One of ours?
>            if (blockers[j] instanceof Breakpoint) {
>                task.requestUnblock(blockers[j]);
>            } else {
>                // Some blocker that we don't know about
>                // System.out.println("Unknown blocker " +
> blockers[j].toString());
>                // return false;
>            }
>        }
>        return true;
>    }
> 
> I'm not sure what is happening here, but the underlying code should
> operate as:
> -> process hits a breakpoint instruction
> -> all low-level CodeObservers fire
> -> all corresponding high-level Breakpoint observers fire
> -> Breakpoint observers each notify Stepping engine to stop (accompanied
> by corresponding low-level CodeObserver doing the block)
> This will leave the SteppingEngine with a full list of CodeObservers to
> unblock without needing to poke around an assumed live task's internal
> state.
I was going on the theory that it would be better to not have to
interact with the stepping engine when setting breakpoints. I see below
that you're after the same thing, which we talked about, so I'm
surprised that you want breakpoints to depend on the stepping engine at all.

> 
> The flexibility of this approach also lets us write custom high-level
> breakpoint observers, in the monitor say, that can be implemented using
> just the Breakpoint and its shared-library Manager, and not have to
> worry about the stepping engine at all.
>

Should the stepping engine be able to step from/over any blocker, or
only breakpoints?

Tim
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