Hi Chris,

    this won't work as written.  Suspending the active process within a
critical: block prevents the critical: block from completing and releasing
the lock.  So with the changes as written another debugger won't open when
one is already open.

One should never do this:

      aMutexOrSemaphore critical:
            [self doStuff.
             Processor activeProcess suspend]

I'm revising these cases to pull the suspend out of the critical block.

On Tue, Apr 4, 2017 at 1:49 PM, <commits at source.squeak.org> wrote:

> Chris Muller uploaded a new version of Tools to project The Trunk:
> http://source.squeak.org/trunk/Tools-cmm.755.mcz
>
> ==================== Summary ====================
>
> Name: Tools-cmm.755
> Author: cmm
> Time: 4 April 2017, 3:49:36.354898 pm
> UUID: d6acf9c9-c3e4-4076-b2a5-9757eefe0b0e
> Ancestors: Tools-eem.754
>
> Fix the race condition introduced with Debugger>>'ErrorRecursion' which
> resulted in the Emergency Evaluator being opened too eagerly (and unable to
> be closed!) -- even when there was no recursion.
>
> =============== Diff against Tools-eem.754 ===============
>
> Item was changed:
>   CodeHolder subclass: #Debugger
>         instanceVariableNames: 'interruptedProcess interruptedController
> contextStack contextStackIndex contextStackList receiverInspector
> contextVariablesInspector externalInterrupt proceedValue selectingPC
> savedCursor isolationHead failedProject errorWasInUIProcess labelString
> message untilExpression'
> +       classVariableNames: 'ContextStackKeystrokes ErrorRecursion
> ErrorRecursionGuard ErrorReportServer InterruptUIProcessIfBlockedOnErrorInBackgroundProcess
> WantsAnnotationPane'
> -       classVariableNames: 'ContextStackKeystrokes ErrorRecursion
> ErrorReportServer InterruptUIProcessIfBlockedOnErrorInBackgroundProcess
> WantsAnnotationPane'
>         poolDictionaries: ''
>         category: 'Tools-Debugger'!
>
>   !Debugger commentStamp: '<historical>' prior: 0!
>   I represent the machine state at the time of an interrupted process. I
> also represent a query path into the state of the process. The debugger is
> typically viewed through a window that views the stack of suspended
> contexts, the code for, and execution point in, the currently selected
> message, and inspectors on both the receiver of the currently selected
> message, and the variables in the current context.
>
>   Special note on recursive errors:
>   Some errors affect Squeak's ability to present a debugger.  This is
> normally an unrecoverable situation.  However, if such an error occurs in
> an isolation layer, Squeak will attempt to exit from the isolation layer
> and then present a debugger.  Here is the chain of events in such a
> recovery.
>
>         * A recursive error is detected.
>         * The current project is queried for an isolationHead
>         * Changes in the isolationHead are revoked
>         * The parent project of isolated project is returned to
>         * The debugger is opened there and execution resumes.
>
>   If the user closes that debugger, execution continues in the outer
> project and layer.  If, after repairing some damage, the user proceeds from
> the debugger, then the isolationHead is re-invoked, the failed project is
> re-entered, and execution resumes in that world. !
>
> Item was changed:
>   ----- Method: Debugger class>>initialize (in category 'class
> initialization') -----
>   initialize
>         ErrorRecursion := false.
> +       ErrorRecursionGuard := Mutex new.
>         ContextStackKeystrokes := Dictionary new
>                 at: $e put: #send;
>                 at: $t put: #doStep;
>                 at: $T put: #stepIntoBlock;
>                 at: $p put: #proceed;
>                 at: $r put: #restart;
>                 at: $f put: #fullStack;
>                 at: $w put: #where;
>                 yourself.
>
>         "Debugger initialize"!
>
> Item was changed:
> + (PackageInfo named: 'Tools') postscript: 'Debugger initialize.'!
> - (PackageInfo named: 'Tools') postscript: 'ProcessBrowser initialize.'!
>
>
>


-- 
_,,,^..^,,,_
best, Eliot
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