author | Claus Gittinger <cg@exept.de> |
Wed, 25 Aug 1999 18:21:24 +0200 | |
changeset 4633 | b6908af8f900 |
parent 4437 | 212260fce312 |
child 4902 | caf73c9821c5 |
permissions | -rw-r--r-- |
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" |
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COPYRIGHT (c) 1993 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:#Semaphore |
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instanceVariableNames:'count waitingProcesses lastOwnerID name' |
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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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!Semaphore class methodsFor:'documentation'! |
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copyright |
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" |
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COPYRIGHT (c) 1993 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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Semaphores are used to synchronize processes providing a nonBusy wait |
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mechanism. A process can wait for the availability of some resource by |
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performing a Semaphore>>wait, which will suspend the process until the |
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resource becomes available. Signalling is done by (another process performing) |
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Semaphore>>signal. |
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If the resource has been already available before the wait, no suspending is |
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done, but the resource immediately allocated. |
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There are also semaphores for mutual access to a critical region |
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(Semaphore>>forMutualExclusion and Semaphore>>critical:). |
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Additional protocol is provided for oneShot semaphores, |
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(#signalOnce) and for conditional signalling (#signalIf). |
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You can also attach semaphores to external events (such as I/O arrival or |
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timer events). |
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This is done by telling the Processor to signal the semaphore |
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under some condition. |
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See 'Processor>>signal:afterSeconds:', 'Processor>>signal:onInput:' etc. |
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See examples in doc/coding (found in the CodingExamples-nameSpace). |
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Warning/Note/Hint: |
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a Semaphore-forMutualExclusion does NEVER allow for the critical |
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region to be entered twice - NOT EVEN by the same process. |
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That means, that a recursive attempt to enter that section leads |
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to a deadlock. |
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Use a RecursionLock instead of a semaphore to avoid this. |
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[instance variables:] |
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count <SmallInteger> the number of waits, that will go through |
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without blocking. |
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Incremented on #signal; decremented on #wait. |
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waitingProcesses <OrderedCollection> waiting processes - will be served first |
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come first served when signalled. |
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lastOwnerID <SmallInteger> a debugging aid: set when count drops |
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to zero to the current processes id. |
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Helps in finding deadlocks. |
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name <String> a debugging aid: an optional userFriendly |
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name; helps to identify a semaphore easier. |
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[see also:] |
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SemaphoreSet RecursionLock Monitor |
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SharedQueue Delay |
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Process ProcessorScheduler |
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[author:] |
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Claus Gittinger |
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" |
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! |
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||
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examples |
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" |
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two processes synchronizing on a sema: |
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[exBegin] |
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|sema thread1 thread2| |
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sema := Semaphore new. |
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thread1 := [ |
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Transcript showCR:'here is thread 1; now waiting ...'. |
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sema wait. |
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Transcript showCR:'here is thread 1 again.'. |
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] newProcess. |
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thread2 := [ |
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Transcript showCR:'here is thread 2; delaying a bit ...'. |
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Delay waitForSeconds:5. |
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Transcript showCR:'here is thread 2 again; now signalling the sema'. |
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sema signal. |
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Transcript showCR:'here is thread 2 after the signalling.'. |
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] newProcess. |
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thread1 priority:7. |
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thread2 priority:6. |
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thread1 resume. |
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thread2 resume. |
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[exEnd] |
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semaphore for critical regions: |
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[exBegin] |
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|accessLock| |
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accessLock := Semaphore forMutualExclusion. |
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[ |
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5 timesRepeat:[ |
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Delay waitForSeconds:2. |
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accessLock critical:[ |
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Transcript showCR:'thread1 in critical region'. |
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Delay waitForSeconds:1. |
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Transcript showCR:'thread1 leaving critical region'. |
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]. |
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] |
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] forkAt:5. |
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[ |
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5 timesRepeat:[ |
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Delay waitForSeconds:1. |
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accessLock critical:[ |
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Transcript showCR:'thread2 in critical region'. |
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Delay waitForSeconds:2. |
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Transcript showCR:'thread2 leaving critical region'. |
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]. |
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] |
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] forkAt:4. |
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[exEnd] |
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a deadlock due to recursive enter of a critical region: |
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[exBegin] |
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|accessLock block| |
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accessLock := Semaphore forMutualExclusion. |
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block := [:arg | |
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Transcript showCR:'about to enter'. |
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accessLock critical:[ |
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Transcript showCR:'entered - doing action'. |
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arg value |
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]. |
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Transcript showCR:'left region'. |
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]. |
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block value:[]. 'this works'. |
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block value:[block value:[] ]. 'this deadlocks'. |
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[exEnd] |
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Avoid the deadlock by using a RecursionLock instead: |
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[exBegin] |
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|accessLock block| |
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accessLock := RecursionLock new. |
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block := [:arg | |
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Transcript showCR:'about to enter'. |
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accessLock critical:[ |
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Transcript showCR:'entered - doing action'. |
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arg value |
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]. |
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Transcript showCR:'left region'. |
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]. |
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block value:[]. 'this works'. |
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block value:[block value:[] ]. 'this deadlocks'. |
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[exEnd] |
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" |
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! ! |
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!Semaphore class methodsFor:'instance creation'! |
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forMutualExclusion |
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"create & return a new semaphore which allows exactly one process to |
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wait on it without blocking. This type of semaphore is used |
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for mutual exclusion from critical regions (see #critical:). |
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Also see RecursionLock, to avoid deadlock in case of recursive entered |
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critical regions." |
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^ super new setCount:1; name:'criticalRegionSema' |
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"Modified: / 17.6.1998 / 16:23:09 / cg" |
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! |
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new |
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"create & return a new semaphore which blocks until a signal is sent" |
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^ super new setCount:0 |
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! |
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new:n |
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"create & return a new semaphore which allows n waits before |
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blocking" |
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^ super new setCount:n |
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! ! |
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!Semaphore methodsFor:'friend-class interface'! |
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checkAndRegisterProcess:process |
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"interface for SemaphoreSet. |
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If the semaphore is available, decrement it and return true. |
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Otherwise register our process to be wakened up once the semaphore is available |
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and return false.. |
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" |
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" |
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bad ST/X trick (needs change, when multiProcessor support is added): |
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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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count ~~ 0 ifTrue:[ |
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count := count - 1. |
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count == 0 ifTrue:[ |
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lastOwnerID := Processor activeProcessId. |
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]. |
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^ true |
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]. |
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(waitingProcesses identityIndexOf:process) == 0 ifTrue:[ |
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waitingProcesses add:process. |
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]. |
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^ false |
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"Modified: 14.12.1995 / 10:32:17 / stefan" |
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"Modified: 10.1.1997 / 21:42:18 / cg" |
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! |
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unregisterProcess:process |
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"interface for SemaphoreSet. |
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Unregister our process from the Semaphore" |
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waitingProcesses removeIdentical:process ifAbsent:[]. |
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"Created: 14.12.1995 / 10:31:50 / stefan" |
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"Modified: 1.2.1997 / 12:11:22 / cg" |
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! ! |
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!Semaphore methodsFor:'printing & storing'! |
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displayString |
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"return a string to display the receiver - include the |
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count for your convenience" |
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^ self class name , '(' , count printString , ' name: ' , (name ? 'unnamed') , ')' |
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"Modified: 28.6.1997 / 16:21:09 / cg" |
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! |
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name |
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"return the semaphores userFriendly name" |
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^ name |
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! |
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name:aString |
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"set the semaphores userFriendly name" |
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name := aString |
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! ! |
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!Semaphore methodsFor:'private accessing'! |
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initSignals |
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"set the count of the semaphore to zero. |
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provided for ST-80 compatibility." |
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count := 0 |
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"Created: 17.2.1997 / 11:31:19 / cg" |
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! |
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setCount:n |
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"set the count of the semaphore; |
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thats the number of possible waits, without blocking" |
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waitingProcesses := OrderedCollection new:2. |
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count := n |
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"Modified: 17.2.1997 / 11:36:40 / cg" |
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! ! |
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!Semaphore methodsFor:'queries '! |
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count |
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"return the number of 'already-counted' trigger events. |
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Thats the number of waits which will succeed without blocking" |
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^ count |
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"Created: 23.1.1997 / 02:55:58 / cg" |
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! |
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isEmpty |
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"ST80 compatibility - return true if there are no waiters" |
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^ waitingProcesses isEmpty |
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"Created: / 3.5.1996 / 18:06:27 / cg" |
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"Modified: / 18.6.1998 / 16:07:38 / cg" |
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! |
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lastOwnerId |
325 |
"return the processId of the last owning process |
|
326 |
(the one which counted to zero). |
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327 |
May be very useful in debugging deadLock situations" |
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328 |
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329 |
^ lastOwnerID |
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||
331 |
"Created: 24.1.1997 / 23:09:33 / cg" |
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332 |
! |
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333 |
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numberOfWaitingProcesses |
335 |
"return the number of processes waiting on the receiver" |
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336 |
||
337 |
^ waitingProcesses size |
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338 |
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339 |
"Created: 3.5.1996 / 18:06:27 / cg" |
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! |
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waitingProcesses |
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"return the processes waiting on the receiver" |
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|
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^ waitingProcesses |
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|
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347 |
"Created: 18.7.1996 / 20:53:33 / cg" |
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! |
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|
217 | 350 |
wouldBlock |
351 |
"return true, if the receiver would block the activeProcess |
|
352 |
if a wait was performed. False otherwise." |
|
353 |
||
354 |
^ count == 0 |
|
355 |
! ! |
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356 |
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699 | 357 |
!Semaphore methodsFor:'wait & signal'! |
358 |
||
359 |
critical:aBlock |
|
360 |
"evaluate aBlock as a critical region; the receiver must be |
|
361 |
created using Semaphore>>forMutualExclusion" |
|
362 |
||
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363 |
|retVal gotSema| |
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364 |
|
101239898989
unwind block over wait (in critical)
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|
365 |
[ |
3669 | 366 |
gotSema := self wait. |
367 |
retVal := aBlock value. |
|
1185
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|
368 |
] valueOnUnwindDo:[ |
3669 | 369 |
"/ be careful - the unwind may occur both while waiting |
370 |
"/ AND while evaluating the block. |
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371 |
gotSema notNil ifTrue:[self signal]. |
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1185
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372 |
]. |
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Fix in critical: don't signal a semaphore that we didn't get when unwinding.
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373 |
self signal. |
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374 |
^ retVal |
699 | 375 |
|
376 |
" |
|
377 |
the example below is stupid (it should use a SharedQueue, |
|
378 |
or at least a Queue with critical regions). |
|
379 |
Anyhow, it demonstrates how two processes lock each other |
|
380 |
from accessing coll at the same time |
|
381 |
||
382 |
|sema coll| |
|
383 |
||
384 |
sema := Semaphore forMutualExclusion. |
|
385 |
coll := OrderedCollection new:10. |
|
386 |
||
387 |
[ |
|
3669 | 388 |
1 to:1000 do:[:i | |
389 |
sema critical:[ |
|
390 |
coll addLast:i. |
|
391 |
(Delay forSeconds:0.1) wait. |
|
392 |
] |
|
393 |
] |
|
699 | 394 |
] forkAt:4. |
395 |
||
396 |
[ |
|
3669 | 397 |
1 to:1000 do:[:i | |
398 |
sema critical:[ |
|
399 |
coll removeFirst. |
|
400 |
(Delay forSeconds:0.1) wait. |
|
401 |
] |
|
402 |
] |
|
699 | 403 |
] forkAt:4. |
404 |
" |
|
1185
2b24258b4f24
Fix in critical: don't signal a semaphore that we didn't get when unwinding.
Stefan Vogel <sv@exept.de>
parents:
1122
diff
changeset
|
405 |
|
3669 | 406 |
"Modified: / 16.4.1996 / 10:00:46 / stefan" |
407 |
"Modified: / 21.7.1998 / 17:45:26 / cg" |
|
699 | 408 |
! |
409 |
||
410 |
signal |
|
4633 | 411 |
"waking up (the first) waiter. |
412 |
Q: should this be the highest prio waiter ?" |
|
699 | 413 |
|
3272
3e35f761be17
when signalling multiple process, make ALL of them FIRST runnable
Claus Gittinger <cg@exept.de>
parents:
2723
diff
changeset
|
414 |
|wasBlocked| |
362 | 415 |
|
699 | 416 |
wasBlocked := OperatingSystem blockInterrupts. |
1031 | 417 |
[ |
3836
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
418 |
|p| |
3272
3e35f761be17
when signalling multiple process, make ALL of them FIRST runnable
Claus Gittinger <cg@exept.de>
parents:
2723
diff
changeset
|
419 |
|
3836
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
420 |
count := count + 1. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
421 |
p := waitingProcesses removeFirstIfAbsent:nil. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
422 |
p notNil ifTrue:[ |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
423 |
Processor resume:p. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
424 |
]. |
1031 | 425 |
] valueNowOrOnUnwindDo:[ |
3836
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
426 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
1031 | 427 |
] |
428 |
||
3272
3e35f761be17
when signalling multiple process, make ALL of them FIRST runnable
Claus Gittinger <cg@exept.de>
parents:
2723
diff
changeset
|
429 |
"Modified: / 4.2.1998 / 21:01:07 / cg" |
699 | 430 |
! |
431 |
||
432 |
signalForAll |
|
433 |
"signal the semaphore for all waiters. |
|
434 |
This can be used for process synchronization, if multiple processes are |
|
435 |
waiting for a common event." |
|
436 |
||
437 |
|wasBlocked| |
|
438 |
||
3272
3e35f761be17
when signalling multiple process, make ALL of them FIRST runnable
Claus Gittinger <cg@exept.de>
parents:
2723
diff
changeset
|
439 |
waitingProcesses notEmpty ifTrue:[ |
3392 | 440 |
wasBlocked := OperatingSystem blockInterrupts. |
441 |
[ |
|
442 |
|p| |
|
3272
3e35f761be17
when signalling multiple process, make ALL of them FIRST runnable
Claus Gittinger <cg@exept.de>
parents:
2723
diff
changeset
|
443 |
|
3392 | 444 |
"/ first, make them all runnable, but do not schedule |
445 |
"/ (in case one has higher prio and goes into a wait |
|
446 |
"/ immediately again.) |
|
3272
3e35f761be17
when signalling multiple process, make ALL of them FIRST runnable
Claus Gittinger <cg@exept.de>
parents:
2723
diff
changeset
|
447 |
|
3392 | 448 |
[waitingProcesses notEmpty] whileTrue:[ |
449 |
p := waitingProcesses removeFirst. |
|
450 |
count := count + 1. |
|
451 |
Processor makeRunnable:p. |
|
452 |
]. |
|
453 |
] valueNowOrOnUnwindDo:[ |
|
454 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
455 |
]. |
|
456 |
"/ |
|
457 |
"/ now, reschedule |
|
458 |
"/ |
|
459 |
Processor reschedule |
|
699 | 460 |
] |
1031 | 461 |
|
3272
3e35f761be17
when signalling multiple process, make ALL of them FIRST runnable
Claus Gittinger <cg@exept.de>
parents:
2723
diff
changeset
|
462 |
"Modified: / 5.2.1998 / 10:40:26 / cg" |
699 | 463 |
! |
362 | 464 |
|
699 | 465 |
signalIf |
466 |
"signal the semaphore, but only if being waited upon. |
|
467 |
This can be used for one-shot semaphores (i.e. not remembering |
|
468 |
previous signals)" |
|
469 |
||
470 |
|wasBlocked| |
|
471 |
||
472 |
waitingProcesses notEmpty ifTrue:[ |
|
3392 | 473 |
wasBlocked := OperatingSystem blockInterrupts. |
474 |
[ |
|
475 |
waitingProcesses notEmpty ifTrue:[ |
|
476 |
self signal |
|
477 |
]. |
|
478 |
] valueNowOrOnUnwindDo:[ |
|
479 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
480 |
] |
|
699 | 481 |
] |
1031 | 482 |
|
483 |
"Modified: 28.2.1996 / 21:23:57 / cg" |
|
699 | 484 |
! |
485 |
||
486 |
signalOnce |
|
487 |
"wakeup waiters - but only once. |
|
488 |
I.e. if the semaphore has already been signalled, this |
|
489 |
is ignored." |
|
490 |
||
491 |
|wasBlocked| |
|
492 |
||
493 |
count == 0 ifTrue:[ |
|
3836
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
494 |
wasBlocked := OperatingSystem blockInterrupts. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
495 |
[ |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
496 |
|p| |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
497 |
|
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
498 |
count == 0 ifTrue:[ |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
499 |
count := 1. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
500 |
p := waitingProcesses removeFirstIfAbsent:nil. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
501 |
p notNil ifTrue:[ |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
502 |
Processor resume:p. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
503 |
]. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
504 |
]. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
505 |
] valueNowOrOnUnwindDo:[ |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
506 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
318f7d6f242b
avoid two more sends in signal / signalOnce
Claus Gittinger <cg@exept.de>
parents:
3669
diff
changeset
|
507 |
] |
699 | 508 |
] |
1031 | 509 |
|
510 |
"Modified: 28.2.1996 / 21:24:08 / cg" |
|
699 | 511 |
! |
1 | 512 |
|
513 |
wait |
|
514 |
"wait for the semaphore" |
|
515 |
||
2142 | 516 |
|activeProcess wasBlocked| |
1 | 517 |
|
518 |
" |
|
2262 | 519 |
bad ST/X trick (needs change, when multiProcessor support is added): |
159 | 520 |
this works only since interrupts are only serviced at |
521 |
message send and method-return time .... |
|
2262 | 522 |
If you add a message send between the compare and the decrement, |
523 |
things will go mad ... (especially be careful when adding a debugPrint-here) |
|
93 | 524 |
" |
525 |
count ~~ 0 ifTrue:[ |
|
3600
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
526 |
count := count - 1. |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
527 |
count == 0 ifTrue:[ |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
528 |
lastOwnerID := Processor activeProcessId. |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
529 |
]. |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
530 |
^ self |
93 | 531 |
]. |
532 |
||
2142 | 533 |
activeProcess := Processor activeProcess. |
159 | 534 |
|
302 | 535 |
wasBlocked := OperatingSystem blockInterrupts. |
159 | 536 |
" |
537 |
need a while-loop here, since more than one process may |
|
538 |
wait for it and another one may also wake up. |
|
539 |
Thus, the count is not always non-zero after returning from |
|
540 |
suspend. |
|
541 |
" |
|
1 | 542 |
[count == 0] whileTrue:[ |
3600
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
543 |
waitingProcesses add:activeProcess. |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
544 |
" |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
545 |
for some more descriptive info in processMonitor ... |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
546 |
... set the state to #wait (instead of #suspend) |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
547 |
" |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
548 |
[ |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
549 |
activeProcess suspendWithState:#wait |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
550 |
] valueOnUnwindDo:[ |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
551 |
waitingProcesses removeIdentical:activeProcess ifAbsent:[]. |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
552 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
553 |
]. |
1812
a048a98aa299
kludge around a situation, where one process
Claus Gittinger <cg@exept.de>
parents:
1577
diff
changeset
|
554 |
|
3600
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
555 |
count == 0 ifTrue:[ |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
556 |
"/ care for someone manually resuming me ... |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
557 |
"/ being multiple times on waitingProcesses |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
558 |
waitingProcesses removeIdentical:activeProcess ifAbsent:[]. |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
559 |
] |
1 | 560 |
]. |
10 | 561 |
count := count - 1. |
2262 | 562 |
count == 0 ifTrue:[ |
3600
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
563 |
lastOwnerID := Processor activeProcessId. |
2262 | 564 |
]. |
93 | 565 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
752
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
566 |
|
3600
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
567 |
"Modified: / 13.12.1995 / 13:26:33 / stefan" |
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
568 |
"Modified: / 17.6.1998 / 15:26:27 / cg" |
10 | 569 |
! |
570 |
||
329 | 571 |
waitUncounted |
572 |
"wait for the semaphore; do not consume the resource |
|
573 |
(i.e. do not count down)" |
|
574 |
||
2142 | 575 |
|activeProcess wasBlocked| |
329 | 576 |
|
577 |
" |
|
2262 | 578 |
bad ST/X trick (needs change, when multiProcessor support is added): |
329 | 579 |
this works only since interrupts are only serviced at |
580 |
message send and method-return time .... |
|
2262 | 581 |
If you add a message send between the compare and the decrement, |
582 |
things will go mad ... (especially be careful when adding a debugPrint-here) |
|
329 | 583 |
" |
584 |
count ~~ 0 ifTrue:[ |
|
3392 | 585 |
^ self |
329 | 586 |
]. |
587 |
||
2142 | 588 |
activeProcess := Processor activeProcess. |
329 | 589 |
|
590 |
wasBlocked := OperatingSystem blockInterrupts. |
|
591 |
" |
|
592 |
need a while-loop here, since more than one process may |
|
593 |
wait for it and another one may also wake up. |
|
594 |
Thus, the count is not always non-zero after returning from |
|
595 |
suspend. |
|
596 |
" |
|
597 |
[count == 0] whileTrue:[ |
|
3392 | 598 |
waitingProcesses add:activeProcess. |
599 |
" |
|
600 |
for some more descriptive info in processMonitor ... |
|
601 |
... set the state to #wait (instead of #suspend) |
|
602 |
" |
|
603 |
[ |
|
604 |
activeProcess suspendWithState:#wait |
|
605 |
] valueOnUnwindDo:[ |
|
606 |
waitingProcesses removeIdentical:activeProcess ifAbsent:[]. |
|
607 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
608 |
]. |
|
609 |
count == 0 ifTrue:[ |
|
610 |
"/ care for someone manually resuming me ... |
|
611 |
"/ being multiple times on waitingProcesses |
|
612 |
waitingProcesses removeIdentical:activeProcess ifAbsent:[]. |
|
613 |
] |
|
329 | 614 |
]. |
615 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
752
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
616 |
|
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
617 |
"Modified: 13.12.1995 / 13:26:49 / stefan" |
2352 | 618 |
"Modified: 1.2.1997 / 12:11:41 / cg" |
329 | 619 |
! |
620 |
||
159 | 621 |
waitWithTimeout:seconds |
622 |
"wait for the semaphore, but abort the wait after some time. |
|
2690 | 623 |
return the receiver if the semaphore triggered normal, nil if we return |
926
101239898989
unwind block over wait (in critical)
Claus Gittinger <cg@exept.de>
parents:
770
diff
changeset
|
624 |
due to a timeout. |
101239898989
unwind block over wait (in critical)
Claus Gittinger <cg@exept.de>
parents:
770
diff
changeset
|
625 |
The seconds-argument may be a float (i.e. use 0.1 for a 100ms timeout). |
2690 | 626 |
With zero timeout, this can be used to poll a semaphore (returning |
627 |
the receiver if the semaphore is available, nil if not). |
|
628 |
However, polling is not the intended use of semaphores, though." |
|
159 | 629 |
|
2142 | 630 |
|activeProcess timeoutOccured wasBlocked unblock now endTime| |
159 | 631 |
|
632 |
" |
|
2262 | 633 |
bad ST/X trick (needs change, when multiProcessor support is added): |
159 | 634 |
this works only since interrupts are only serviced at |
635 |
message send and method-return time .... |
|
2262 | 636 |
If you add a message send between the compare and the decrement, |
637 |
things will go mad ... (especially be careful when adding a debugPrint-here) |
|
159 | 638 |
" |
639 |
count ~~ 0 ifTrue:[ |
|
3392 | 640 |
count := count - 1. |
641 |
count == 0 ifTrue:[ |
|
642 |
lastOwnerID := Processor activeProcessId. |
|
643 |
]. |
|
644 |
^ self |
|
159 | 645 |
]. |
646 |
||
647 |
" |
|
648 |
with zero-timeout, this is a poll |
|
649 |
" |
|
650 |
seconds = 0 ifTrue:[ |
|
3392 | 651 |
^ nil |
159 | 652 |
]. |
653 |
||
2142 | 654 |
activeProcess := Processor activeProcess. |
302 | 655 |
|
159 | 656 |
wasBlocked := OperatingSystem blockInterrupts. |
657 |
||
658 |
" |
|
659 |
calculate the end-time |
|
660 |
" |
|
661 |
now := OperatingSystem getMillisecondTime. |
|
662 |
endTime := OperatingSystem millisecondTimeAdd:now and:(seconds * 1000). |
|
663 |
||
2142 | 664 |
unblock := [timeoutOccured := true. Processor resume:activeProcess]. |
665 |
Processor addTimedBlock:unblock for:activeProcess atMilliseconds:endTime. |
|
159 | 666 |
|
667 |
" |
|
668 |
need a while-loop here, since more than one process may |
|
669 |
wait for it and another one may also wake up. |
|
670 |
Thus, the count is not always non-zero after returning from |
|
671 |
suspend. |
|
672 |
" |
|
673 |
[count == 0] whileTrue:[ |
|
3392 | 674 |
waitingProcesses add:activeProcess. |
302 | 675 |
|
3392 | 676 |
timeoutOccured := false. |
677 |
" |
|
678 |
for some more descriptive info in processMonitor ... |
|
679 |
... set the state to #wait (instead of #suspend) |
|
680 |
" |
|
681 |
[ |
|
682 |
activeProcess suspendWithState:#wait. |
|
683 |
] valueOnUnwindDo:[ |
|
684 |
unblock := nil. |
|
685 |
waitingProcesses removeIdentical:activeProcess ifAbsent:[]. |
|
686 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
687 |
]. |
|
159 | 688 |
|
3392 | 689 |
waitingProcesses removeIdentical:activeProcess ifAbsent:[]. |
690 |
timeoutOccured ifTrue:[ |
|
691 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
692 |
unblock := nil. |
|
693 |
^ nil |
|
694 |
]. |
|
159 | 695 |
]. |
696 |
Processor removeTimedBlock:unblock. |
|
2690 | 697 |
unblock := nil. |
698 |
||
159 | 699 |
count := count - 1. |
2262 | 700 |
count == 0 ifTrue:[ |
3392 | 701 |
lastOwnerID := Processor activeProcessId. |
2262 | 702 |
]. |
159 | 703 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
770
402958905760
protocol of waitWithTImeOut: changed
Claus Gittinger <cg@exept.de>
parents:
769
diff
changeset
|
704 |
^ self |
752
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
705 |
|
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
706 |
"Modified: 13.12.1995 / 13:27:24 / stefan" |
2690 | 707 |
"Modified: 16.6.1997 / 21:54:38 / cg" |
699 | 708 |
! ! |
77 | 709 |
|
1812
a048a98aa299
kludge around a situation, where one process
Claus Gittinger <cg@exept.de>
parents:
1577
diff
changeset
|
710 |
!Semaphore class methodsFor:'documentation'! |
183 | 711 |
|
699 | 712 |
version |
4633 | 713 |
^ '$Header: /cvs/stx/stx/libbasic/Semaphore.st,v 1.55 1999-08-25 16:21:24 cg Exp $' |
1 | 714 |
! ! |