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"
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COPYRIGHT (c) 1995 by Claus Gittinger
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All Rights Reserved
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This software is furnished under a license and may be used
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only in accordance with the terms of that license and with the
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inclusion of the above copyright notice. This software may not
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be provided or otherwise made available to, or used by, any
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other person. No title to or ownership of the software is
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hereby transferred.
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"
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Object subclass:#RecursionLock
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instanceVariableNames:'process sema'
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classVariableNames:''
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poolDictionaries:''
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category:'Kernel-Processes'
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!
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!RecursionLock class methodsFor:'documentation'!
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699
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copyright
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"
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COPYRIGHT (c) 1995 by Claus Gittinger
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All Rights Reserved
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This software is furnished under a license and may be used
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only in accordance with the terms of that license and with the
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inclusion of the above copyright notice. This software may not
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be provided or otherwise made available to, or used by, any
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other person. No title to or ownership of the software is
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hereby transferred.
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"
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!
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documentation
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"
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like a Semaphore for mutual exclusion, but avoids the deadlock
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if a critical region is reentered by the same process again.
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I.e. allows reentering the critical region if the current process
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is the one which did the original locking.
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example:
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|lock|
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lock := RecursionLock new.
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lock critical:[
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Transcript showCr:'in lock ...'.
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lock critical:[
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Transcript showCr:'again ...'
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]
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]
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"
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! !
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!RecursionLock class methodsFor:'instance creation'!
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new
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^ self basicNew initialize
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! !
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!RecursionLock methodsFor:'private initialization'!
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initialize
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sema := Semaphore forMutualExclusion
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! !
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!RecursionLock methodsFor:'wait & signal'!
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critical:aBlock
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"evaluate aBlock as a critical region, but do not block,
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if this lock is already held by the current process."
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|active|
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active := Processor activeProcess.
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process == active ifTrue:[
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aBlock value
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] ifFalse:[
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[
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sema critical:[
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process := active.
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aBlock value
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]
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] valueNowOrOnUnwindDo:[
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process := nil
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]
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].
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! !
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!RecursionLock class methodsFor:'documentation'!
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version
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^ '$Header: /cvs/stx/stx/libbasic/RecursionLock.st,v 1.6 1995-12-07 21:30:23 cg Exp $'
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! !
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