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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