author | Claus Gittinger <cg@exept.de> |
Thu, 25 Jul 2013 11:40:25 +0200 | |
changeset 3061 | 3fb64baa8409 |
parent 2961 | 93ab3ea39189 |
child 3062 | fdc6ffd96189 |
permissions | -rw-r--r-- |
272 | 1 |
" |
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COPYRIGHT (c) 1996 by Claus Gittinger |
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83af18019cc9
care for dead process holding a monitor
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parents:
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All Rights Reserved |
272 | 4 |
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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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#valueNowOrOnUnwindDo: -> #ensure:
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"{ Package: 'stx:libbasic2' }" |
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#valueNowOrOnUnwindDo: -> #ensure:
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Object subclass:#Monitor |
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instanceVariableNames:'owningProcess sema count' |
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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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!Monitor class methodsFor:'documentation'! |
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copyright |
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" |
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COPYRIGHT (c) 1996 by Claus Gittinger |
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parents:
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All Rights Reserved |
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|
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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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Monitors (as used in Java) provide a functionality much like RecursionLocks, |
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but are not block based. |
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Therefore, monitors are not unwind-save (i.e. a return or unwind while a |
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monitor is locked, will lead to a deadlock situation). |
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You have to care for unwind protection yourself. |
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Notice: |
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This is an experimental demo class - there is no WARRANTY. |
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Smalltalkers should use Semaphores and RecursionLocks, which |
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are unwind-save. |
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[see also:] |
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RecursionLock Semaphore Delay SharedQueue |
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Block |
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[author:] |
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Claus Gittinger |
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" |
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! |
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examples |
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" |
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[exBegin] |
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|mon p1 p2 p3| |
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mon := Monitor new. |
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p1 := [ |
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10 timesRepeat:[ |
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Delay waitForSeconds:0.3. |
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mon enter. |
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'p1 got it' printNL. |
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Delay waitForSeconds:0.3. |
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'p1 leaves' printNL. |
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mon exit |
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] |
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] fork. |
272 | 77 |
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p2 := [ |
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20 timesRepeat:[ |
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Delay waitForSeconds:0.2. |
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mon enter. |
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'p2 got it' printNL. |
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parents:
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Delay waitForSeconds:0.2. |
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parents:
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'p2 leaves' printNL. |
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mon exit |
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parents:
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] |
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] fork. |
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p3 := [ |
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30 timesRepeat:[ |
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parents:
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Delay waitForSeconds:0.1. |
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parents:
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mon enter. |
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'p3 got it' printNL. |
83af18019cc9
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parents:
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Delay waitForSeconds:0.1. |
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parents:
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'p3 leaves' printNL. |
83af18019cc9
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parents:
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mon exit |
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] |
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] fork. |
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[exEnd] |
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" |
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! ! |
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!Monitor class methodsFor:'instance creation'! |
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new |
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^ self basicNew initialize |
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! ! |
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!Monitor methodsFor:'enter & leave'! |
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critical: aBlock |
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"a critical section. Executes a block as a critical section, secured by the receiver." |
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^ [ |
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self enter. |
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aBlock value |
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] ensure:[ |
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self exit |
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] |
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! |
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enter |
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"enter the monitor" |
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|thisProcess wasBlocked| |
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thisProcess := Processor activeProcess. |
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" |
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this works only since interrupts are only serviced at |
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message send and method-return time .... |
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If you add a message send into the ifTrue:-block, things will |
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go mad ... (especially be careful when adding a debugPrint-here) |
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" |
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owningProcess isNil ifTrue:[ |
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count := 1. |
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owningProcess := thisProcess. |
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^ self |
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]. |
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owningProcess == thisProcess ifTrue:[ |
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count := count + 1. |
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^ self |
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]. |
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wasBlocked := OperatingSystem blockInterrupts. |
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[ |
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owningProcess isDead ifTrue:[ |
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'Monitor [warning]: entering monitor owned by dead process' errorPrintCR. |
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"/ self halt. |
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] ifFalse:[ |
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[owningProcess notNil] whileTrue:[ |
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thisProcess state:#monWait. |
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(sema waitWithTimeout:10) isNil ifTrue:[ |
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(owningProcess notNil and:[owningProcess isDead]) ifTrue:[ |
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'Monitor [warning]: aquire monitor from dead process' errorPrintCR. |
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owningProcess := nil. |
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] |
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] |
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]. |
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]. |
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count := 1. |
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owningProcess := thisProcess. |
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] ensure:[ |
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wasBlocked ifFalse:[OperatingSystem unblockInterrupts] |
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] |
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"Modified: / 8.1.1999 / 13:56:28 / cg" |
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! |
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exit |
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"exit the monitor" |
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|thisProcess| |
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count == 0 ifTrue:[ |
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'MONITOR [info]: already left' errorPrintCR. |
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^ self |
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]. |
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thisProcess := Processor activeProcess. |
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" |
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this works only since interrupts are only serviced at |
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message send and method-return time .... |
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If you add a message send into the ifTrue:-block, things will |
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go mad ... (especially be careful when adding a debugPrint-here) |
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" |
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owningProcess ~~ thisProcess ifTrue:[ |
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self halt:'invalid exit' |
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]. |
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count := count - 1. |
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count ~~ 0 ifTrue:[ ^ self]. |
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owningProcess := nil. |
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sema signal. |
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"Modified: 21.8.1997 / 16:44:17 / cg" |
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! |
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fakeEnter:aProcess count:additionalCount |
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"(fake-)enter the monitor, without blocking. |
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Raises an error, if the monitor is not free and owned by another process" |
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|wasBlocked| |
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" |
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this works only since interrupts are only serviced at |
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message send and method-return time .... |
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If you add a message send into the ifTrue:-block, things will |
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go mad ... (especially be careful when adding a debugPrint-here) |
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" |
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owningProcess isNil ifTrue:[ |
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count := additionalCount. |
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owningProcess := aProcess. |
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^ self |
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]. |
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220 |
wasBlocked := OperatingSystem blockInterrupts. |
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owningProcess == aProcess ifTrue:[ |
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count := count + additionalCount. |
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224 |
wasBlocked ifFalse:[ OperatingSystem unblockInterrupts]. |
718 | 225 |
^ self |
226 |
]. |
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227 |
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228 |
owningProcess isDead ifTrue:[ |
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'Monitor [warning]: (fake)entering monitor owned by dead process' errorPrintCR. |
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"/ self halt. |
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owningProcess := aProcess. |
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count := additionalCount. |
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wasBlocked ifFalse:[ OperatingSystem unblockInterrupts]. |
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^ self |
235 |
]. |
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wasBlocked ifFalse:[ OperatingSystem unblockInterrupts]. |
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self error:'Cannot fakeEnter monitor owned by another process'. |
239 |
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240 |
"Created: / 8.1.1999 / 13:54:44 / cg" |
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"Modified: / 8.1.1999 / 13:57:42 / cg" |
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! ! |
243 |
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244 |
!Monitor methodsFor:'initialization'! |
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initialize |
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sema := Semaphore new name:'monitorSema'. |
272 | 248 |
count := 0. |
249 |
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250 |
"Created: 3.5.1996 / 17:24:59 / cg" |
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251 |
! ! |
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252 |
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273 | 253 |
!Monitor methodsFor:'queries'! |
254 |
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count |
256 |
owningProcess isNil ifTrue:[^ 0]. |
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^ count |
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258 |
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259 |
"Created: / 8.1.1999 / 13:59:30 / cg" |
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"Modified: / 8.1.1999 / 14:00:01 / cg" |
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! |
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273 | 263 |
isFree |
264 |
"return true, if the monitor is free |
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(i.e. noone waits and count is zero)" |
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266 |
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267 |
|wasBlocked ret| |
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268 |
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718 | 269 |
owningProcess isNil ifTrue:[^ true]. |
270 |
count == 0 ifTrue:[^ true]. |
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271 |
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273 | 272 |
ret := true. |
273 |
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274 |
wasBlocked := OperatingSystem blockInterrupts. |
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275 |
owningProcess notNil ifTrue:[ |
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718 | 276 |
ret := false |
273 | 277 |
] ifFalse:[ |
718 | 278 |
sema numberOfWaitingProcesses ~~ 0 ifTrue:[ret := false]. |
273 | 279 |
]. |
280 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
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281 |
^ ret. |
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||
718 | 283 |
"Created: / 3.5.1996 / 18:08:38 / cg" |
284 |
"Modified: / 8.1.1999 / 13:59:53 / cg" |
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710 | 285 |
! |
286 |
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287 |
owningProcess |
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288 |
"return the monitors owner; or nil, if its free" |
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289 |
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290 |
^ owningProcess |
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292 |
"Created: / 11.12.1998 / 13:43:39 / cg" |
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273 | 293 |
! ! |
294 |
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560 | 295 |
!Monitor class methodsFor:'documentation'! |
272 | 296 |
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297 |
version |
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^ '$Header: /cvs/stx/stx/libbasic2/Monitor.st,v 1.18 2013-07-25 09:40:25 cg Exp $' |
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! ! |
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