Excellent, thank you! I've been wanting an example which makes this 
problem happen reliably for a while now. I'll look at it.

Cheers,
   - Andreas

Simon Kirk wrote:
> Hi all. We've been playing with Semaphores and Delays recently, as we 
> were having some problems with said issues. We tried installing Andreas' 
> fixes, but if we do, the code below yields some strange results when 
> evaluated in a workspace:
> 
> 
> s _ Semaphore forMutualExclusion.
> i _ 1.
> 
> "Loop while there's not too many signals on the semaphore (should be 0 
> or 1)"
> [(s instVarNamed: #excessSignals) < 2] whileTrue: [
> 
> "Fork two processes to do things inside the semaphore"
> p _ [[true] whileTrue: [s critical: [(Delay forMilliseconds: 10) wait]]]
>     forkNamed: 'p', i printString.
>     
> q _ [[true] whileTrue: [s critical: [(Delay forMilliseconds: 10) wait]]]
>     forkNamed: 'q', i printString.
> 
> "Increment the counter just to make it easy to ID the processes"
> i _ i + 1.
> 
> "Delay to give the processes a chance to resume and potentially get into 
> the critical on the Semaphore"
> (Delay forMilliseconds: 500 atRandom) wait.
> p terminate.
> (Delay forMilliseconds: 500 atRandom) wait.
> q terminate.
> 
> "After terminating the two processes, the excess signals should be 1 on 
> the Semaphore because
> nothing is in critical any more, assuming the processes terminated 
> properly and the unwind happened
> as it should, but... "
> 
> "In our images with Andreas' recent Delay and Semaphore fixes, we always 
> get one of these two
> error conditions (although normally too many signals). This would cause 
> deadlock in 'real world' situations"
> (s instVarNamed: #excessSignals) = 0 ifTrue: [
>     WorldState addDeferredUIMessage: [self inform: 'Too few signals 
> after ', i printString, ' loops']]].
> self inform: 'Too many signals after ', i printString, ' loops'.
> 
> 
> Don't know if we've done something wrong here, but if not I hope it may 
> give cleverer people than me some more pointers to the root of the whole 
> Semaphore problem :)
> 
> S
> 
> 
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