On 9/10/2010 9:33 PM, Florin Mateoc wrote:
>  On 9/10/2010 7:48 AM, David T. Lewis wrote:
>> Well, we still have some work to do to get ControlManager>>interruptName:preemptedProcess:
>> working right. Background is at http://bugs.squeak.org/view.php?id=1041
>> but the basic idea is that all four of the following should be interruptable:
>>
>>    "[true] whileTrue"
>>    "[[true] whileTrue] forkAt: Processor userSchedulingPriority + 1"
>>    "Smalltalk createStackOverflow"
>>    "[Smalltalk createStackOverflow] forkAt: Processor userSchedulingPriority + 1"
>>
>> I spent some time trying to get this working last night, but have not yet
>> come up with a solution. The basic idea is if the low space interrupt watcher
>> process has called #interruptName:preemptedProcess: passing it theInterruptedProcess,
>> then we want the debugger to open on theInterruptedProcess rather than on
>> activeControllerProcess. This is a bit tricky to debug for obvious reasons ;)
>>
>> Dave
>>
> Of course that if we pass the preempted process, we have to honor that request.
> But I am not sure if I understand correctly. If I have a runaway non-ui process, I don't think that the user interrupt
> should try to find it and interrupt it. I think user interrupt is and should be dedicated to the ui process. Now once
> you open a debugger, you can have a list of currently running processes from which you can select and debug.
>
> Florin
>
>

Hi all,

I have been thinking of a way to have our cake and eat it too (being also able to interrupt a runaway process running at
a priority higher than the ui).
Basically we should have a way to tell Squeak that we want to interrupt the preempted process instead of the
activeControllerProcess.
For example the method #handleUserInterrupt could split the user interrupts into "normal" ones and "emergency" ones. The
code would look like:

handleUserInterrupt

    | preemptedProcess |
   
    Preferences cmdDotEnabled ifTrue: [
        (Sensor shiftPressed and: [(preemptedProcess := Processor preemptedProcess) notNil])
            ifTrue: [
                [Project current
                    interruptName: 'Emergency User Interrupt'
                    preemptedProcess: preemptedProcess] fork]
            ifFalse: [
                [Project current interruptName: 'User Interrupt'] fork]]

Unfortunately the interrupt does not trigger if I also press Shift. Is there a simple way to make it trigger regardless
if Shift is pressed or not?

With this occasion, I also noticed that the method ProcessorScheduler>>preemptedProcess starts looking at the same
priority as the active process.
But a process cannot preempt another process at the same priority, therefore the method is either buggy or poorly named.

Both these tests return true:

| p | p := [[true] whileTrue: [Processor yield]] fork.
p name: 'bla'.
Processor yield.
Processor preemptedProcess == p

| p | p := [[true] whileTrue: [(Delay forMilliseconds: 2) wait]] fork.
p name: 'bla'.
Processor yield.
Processor preemptedProcess == p

(I named the processes to be able to terminate them after the test, so that I don't lose control over the image (Process
allInstances do: [:e | e name = 'bla' ifTrue: [e terminate]]))

Anyway, in both cases, these so-called preempted processes were not actually preempted, they were just nice citizens and
cooperative, so they yielded respectively waited.
I think the method #preemptedProcess should start iterating from "activeProcess priority - 1"

Cheers,
Florin