author | Stefan Vogel <sv@exept.de> |
Tue, 21 Sep 2004 20:06:25 +0200 | |
changeset 8569 | 657853ae04cd |
parent 7718 | 657b832f54a3 |
child 8617 | 5fb5a717deff |
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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"{ Package: 'stx:libbasic' }" |
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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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parents:
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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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The resource internally keeps a count, the number of times the resource can be |
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allocated. If the semaphore is created with a count greater than 1, the sema |
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can be waited-upon that many times without blocking. |
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On the other hand, if initialized with a negative count, the semaphore |
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must be signalled that many times more often in order for a wait to not block. |
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In other words: whenever the semaphore has a count greater than zero, |
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the wait operation will proceed. Otherwise, it will block until the count has |
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been incremented by signal operations to be greater than zero. |
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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, to avoid this. |
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Hint: |
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now (Jul2002), Semaphores now allow for a negative count; this allows for |
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a sync-point to be implemented easily (i.e. to wait for multiple other processes |
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to arrive at a sync-point). |
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See examples. |
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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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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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Wait for multiple processes to arrive at a sync-point: |
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[exBegin] |
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|syncSema proceedSema thread1 thread2 thread3| |
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syncSema := Semaphore new. |
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syncSema setCount:(1-3). |
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proceedSema := Semaphore new. |
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thread1 := [ |
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Transcript showCR:'here is thread 1; now busy ...'. |
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Delay waitForSeconds:(2 + (Random nextIntegerBetween:2 and:4)). |
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Transcript showCR:'here is thread 1 again - now syncing.'. |
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syncSema signal. |
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Transcript showCR:'thread 1 is waiting for all others...'. |
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proceedSema wait. |
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Transcript showCR:'thread 1 done.'. |
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] newProcess. |
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thread2 := [ |
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Transcript showCR:'here is thread 2; now busy ...'. |
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Delay waitForSeconds:(3 + (Random nextIntegerBetween:2 and:4)). |
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Transcript showCR:'here is thread 2 again - now syncing.'. |
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syncSema signal. |
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Transcript showCR:'thread 2 is waiting for all others...'. |
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proceedSema wait. |
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Transcript showCR:'thread 2 done.'. |
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] newProcess. |
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thread3 := [ |
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Transcript showCR:'here is thread 3; now busy ...'. |
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Delay waitForSeconds:(4 + (Random nextIntegerBetween:2 and:4)). |
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Transcript showCR:'here is thread 3 again - now syncing.'. |
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syncSema signal. |
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Transcript showCR:'thread 3 is waiting for all others...'. |
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proceedSema wait. |
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Transcript showCR:'thread 3 done.'. |
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] newProcess. |
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thread1 priority:7. |
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thread2 priority:6. |
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thread3 priority:9. |
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thread1 resume. |
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thread2 resume. |
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thread3 resume. |
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Transcript showCR:'main thread: now waiting for other threads...'. |
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syncSema wait. |
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Transcript showCR:'main thread: all other threads at syncPoint.'. |
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Delay waitForSeconds:2. |
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Transcript showCR:'main thread: now let them proceed...'. |
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proceedSema signalForAll. |
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Transcript showCR:'main thread: done.'. |
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[exEnd] |
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waitWithTimeout:0 can also be used to conditionally aquire the semaphore |
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i.e. only aquire it if its available. |
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|s| |
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s := Semaphore new. |
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[ |
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(s waitWithTimeout:0) notNil ifTrue:[ |
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Transcript showCR:'process1 got the sema'. |
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Delay waitForSeconds:1. |
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Transcript showCR:'process1 signals sema'. |
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s signal. |
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] ifFalse:[ |
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Transcript showCR:'process1 has NOT got the sema'. |
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]. |
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] fork. |
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[ |
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(s waitWithTimeout:0) notNil ifTrue:[ |
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Transcript showCR:'process2 got the sema'. |
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Delay waitForSeconds:1. |
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Transcript showCR:'process2 signals sema'. |
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s signal. |
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] ifFalse:[ |
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Transcript showCR:'process2 has NOT got the sema'. |
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] |
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] fork. |
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s signal. |
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Delay waitForSeconds:0.5. |
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Transcript showCR:'master waits for sema'. |
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s wait. |
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Transcript showCR:'master got the sema'. |
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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:'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'! |
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addWaitingProcess:aProcess |
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"add aProcess to the list of waiting processes. |
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diff
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all processes are ordered first-come-first-serve. |
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NOTE: must be called with blocked interrupts" |
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|
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"for now" |
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parents:
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diff
changeset
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waitingProcesses isNil ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
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parents:
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diff
changeset
|
354 |
waitingProcesses := Array with:aProcess |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
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parents:
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diff
changeset
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355 |
] ifFalse:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
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parents:
7258
diff
changeset
|
356 |
waitingProcesses class == Array ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
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parents:
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diff
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357 |
waitingProcesses := OrderedCollection withAll:waitingProcesses. |
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tuning - although ugly, the speedup of critical: is > 30%
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parents:
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diff
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]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
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parents:
7258
diff
changeset
|
359 |
waitingProcesses add:aProcess. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
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diff
changeset
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360 |
]. |
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parents:
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diff
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361 |
|
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tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
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|
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"/ "Sort, so that higher priority process are resumed first. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
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diff
changeset
|
363 |
"/ Processes having the same priority are ordered first-come-first-serve." |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
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|
364 |
"/ |
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365 |
"/ |priority insertIndex| |
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Isolate waitProcesses (prepare for sorting by prio)
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parents:
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366 |
"/ |
d2ef4d62861e
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parents:
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diff
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367 |
"/ (waitingProcesses size == 0 |
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"/ or:[(priority := aProcess priority) <= waitingProcesses last priority]) ifTrue:[ |
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"/ waitingProcesses add:aProcess. |
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"/ ^ self. |
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
371 |
"/ ]. |
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
372 |
"/ |
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
373 |
"/ insertIndex := waitingProcesses findFirst:[:process| process priority < priority]. |
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
374 |
"/ waitingProcesses add:aProcess beforeIndex:insertIndex. |
7717
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
375 |
! |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
376 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
377 |
removeFirstWaitingProcess |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
378 |
"remove the first waiting process from the list of waiting processes |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
379 |
and return it; Nil if there is none. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
380 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
381 |
NOTE: must be called with blocked interrupts" |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
382 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
383 |
|nWaiting p| |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
384 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
385 |
nWaiting := waitingProcesses size. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
386 |
nWaiting == 0 ifTrue:[^ nil]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
387 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
388 |
nWaiting == 1 ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
389 |
p := waitingProcesses at:1. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
390 |
waitingProcesses := nil. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
391 |
^ p. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
392 |
]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
393 |
^ waitingProcesses removeFirst. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
394 |
! |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
395 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
396 |
removeWaitingProcess:aProcess |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
397 |
"remove aProcess from the list of waiting processes |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
398 |
NO action if it is not in the list. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
399 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
400 |
NOTE: must be called with blocked interrupts" |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
401 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
402 |
|nWaiting| |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
403 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
404 |
nWaiting := waitingProcesses size. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
405 |
nWaiting == 0 ifTrue:[^ self]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
406 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
407 |
nWaiting == 1 ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
408 |
(waitingProcesses at:1) == aProcess ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
409 |
waitingProcesses := nil. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
410 |
]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
411 |
^ self. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
412 |
]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
413 |
waitingProcesses removeIdentical:aProcess ifAbsent:[]. |
6986
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
414 |
! ! |
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
415 |
|
7258 | 416 |
!Semaphore methodsFor:'private-accessing'! |
1 | 417 |
|
8569 | 418 |
clear |
419 |
"clear the semaphores count" |
|
420 |
||
421 |
count := 0 |
|
422 |
! |
|
423 |
||
2407
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
424 |
initSignals |
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
425 |
"set the count of the semaphore to zero. |
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
426 |
provided for ST-80 compatibility." |
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
427 |
|
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
428 |
count := 0 |
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
429 |
|
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
430 |
"Created: 17.2.1997 / 11:31:19 / cg" |
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
431 |
! |
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
432 |
|
1 | 433 |
setCount:n |
2142 | 434 |
"set the count of the semaphore; |
435 |
thats the number of possible waits, without blocking" |
|
436 |
||
7717
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
437 |
waitingProcesses := nil. |
1 | 438 |
count := n |
2142 | 439 |
|
2407
6b0e21391915
added #initSignals for ST-80 compatibility.
Claus Gittinger <cg@exept.de>
parents:
2352
diff
changeset
|
440 |
"Modified: 17.2.1997 / 11:36:40 / cg" |
1 | 441 |
! ! |
442 |
||
5256 | 443 |
!Semaphore methodsFor:'queries'! |
217 | 444 |
|
2235 | 445 |
count |
446 |
"return the number of 'already-counted' trigger events. |
|
447 |
Thats the number of waits which will succeed without blocking" |
|
448 |
||
449 |
^ count |
|
450 |
||
451 |
"Created: 23.1.1997 / 02:55:58 / cg" |
|
452 |
! |
|
453 |
||
2265 | 454 |
lastOwnerId |
455 |
"return the processId of the last owning process |
|
456 |
(the one which counted to zero). |
|
457 |
May be very useful in debugging deadLock situations" |
|
458 |
||
459 |
^ lastOwnerID |
|
460 |
||
461 |
"Created: 24.1.1997 / 23:09:33 / cg" |
|
462 |
! |
|
463 |
||
1329 | 464 |
numberOfWaitingProcesses |
465 |
"return the number of processes waiting on the receiver" |
|
466 |
||
467 |
^ waitingProcesses size |
|
468 |
||
469 |
"Created: 3.5.1996 / 18:06:27 / cg" |
|
470 |
! |
|
471 |
||
1577
720f14f90e2c
access to waitingProcesses added
Claus Gittinger <cg@exept.de>
parents:
1329
diff
changeset
|
472 |
waitingProcesses |
720f14f90e2c
access to waitingProcesses added
Claus Gittinger <cg@exept.de>
parents:
1329
diff
changeset
|
473 |
"return the processes waiting on the receiver" |
720f14f90e2c
access to waitingProcesses added
Claus Gittinger <cg@exept.de>
parents:
1329
diff
changeset
|
474 |
|
7717
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
475 |
^ waitingProcesses ? #() |
1577
720f14f90e2c
access to waitingProcesses added
Claus Gittinger <cg@exept.de>
parents:
1329
diff
changeset
|
476 |
|
720f14f90e2c
access to waitingProcesses added
Claus Gittinger <cg@exept.de>
parents:
1329
diff
changeset
|
477 |
"Created: 18.7.1996 / 20:53:33 / cg" |
8569 | 478 |
! ! |
479 |
||
480 |
!Semaphore methodsFor:'semaphoreSet interface'! |
|
481 |
||
482 |
checkAndAddWaitingProcess:process |
|
483 |
"interface for SemaphoreSet. |
|
484 |
If the semaphore is available, decrement it and return true. |
|
485 |
Otherwise register our process to be wakened up once the semaphore is available |
|
486 |
and return false. |
|
487 |
ATTENTION: this must be invoked with OperatingSystem-interrupts-blocked. |
|
488 |
" |
|
489 |
||
490 |
count > 0 ifTrue:[ |
|
491 |
count := count - 1. |
|
492 |
count == 0 ifTrue:[ |
|
493 |
lastOwnerID := Processor activeProcessId. |
|
494 |
]. |
|
495 |
^ true |
|
496 |
]. |
|
497 |
(waitingProcesses notNil and:[(waitingProcesses includesIdentical:process)]) ifFalse:[ |
|
498 |
self addWaitingProcess:process. |
|
499 |
]. |
|
500 |
^ false |
|
501 |
||
502 |
"Modified: 14.12.1995 / 10:32:17 / stefan" |
|
503 |
"Modified: 10.1.1997 / 21:42:18 / cg" |
|
504 |
! ! |
|
505 |
||
506 |
!Semaphore methodsFor:'signaling'! |
|
507 |
||
508 |
signal |
|
509 |
"waking up (the first) waiter. |
|
510 |
Q: should this be the highest prio waiter ?" |
|
511 |
||
512 |
|wasBlocked| |
|
513 |
||
514 |
wasBlocked := OperatingSystem blockInterrupts. |
|
515 |
[ |
|
516 |
|p| |
|
517 |
||
518 |
count := count + 1. |
|
519 |
waitingProcesses notNil ifTrue:[ |
|
520 |
p := self removeFirstWaitingProcess. |
|
521 |
p notNil ifTrue:[ |
|
522 |
Processor resume:p. |
|
523 |
]. |
|
524 |
]. |
|
525 |
] ensure:[ |
|
526 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
527 |
] |
|
528 |
||
529 |
"Modified: / 4.2.1998 / 21:01:07 / cg" |
|
530 |
! |
|
531 |
||
532 |
signalForAll |
|
533 |
"signal the semaphore for all waiters. |
|
534 |
This can be used for process synchronization, if multiple processes are |
|
535 |
waiting for a common event." |
|
536 |
||
537 |
|wasBlocked| |
|
538 |
||
539 |
waitingProcesses size ~~ 0 ifTrue:[ |
|
540 |
wasBlocked := OperatingSystem blockInterrupts. |
|
541 |
[ |
|
542 |
|processes| |
|
543 |
||
544 |
"first, make them all runnable, but do not schedule |
|
545 |
(in case one has higher prio and goes into a wait immediately again.)" |
|
546 |
||
547 |
processes := waitingProcesses. |
|
548 |
waitingProcesses := nil. |
|
549 |
processes do:[:eachWaitingProcess| |
|
550 |
count := count + 1. |
|
551 |
Processor makeRunnable:eachWaitingProcess. |
|
552 |
]. |
|
553 |
] ensure:[ |
|
554 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
555 |
]. |
|
556 |
"now, schedule the highest priority process" |
|
557 |
Processor reschedule |
|
558 |
] |
|
559 |
||
560 |
"Modified: / 5.2.1998 / 10:40:26 / cg" |
|
561 |
! |
|
562 |
||
563 |
signalIf |
|
564 |
"signal the semaphore, but only if being waited upon. |
|
565 |
This can be used for one-shot semaphores (i.e. not remembering |
|
566 |
previous signals)" |
|
567 |
||
568 |
|wasBlocked| |
|
569 |
||
570 |
waitingProcesses notNil ifTrue:[ |
|
571 |
wasBlocked := OperatingSystem blockInterrupts. |
|
572 |
[ |
|
573 |
waitingProcesses size ~~ 0 ifTrue:[ |
|
574 |
self signal |
|
575 |
]. |
|
576 |
] ensure:[ |
|
577 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
578 |
] |
|
579 |
] |
|
580 |
||
581 |
"Modified: 28.2.1996 / 21:23:57 / cg" |
|
582 |
! |
|
583 |
||
584 |
signalOnce |
|
585 |
"wakeup waiters - but only once. |
|
586 |
I.e. if the semaphore has already been signalled, this is ignored." |
|
587 |
||
588 |
|wasBlocked| |
|
589 |
||
590 |
count <= 0 ifTrue:[ |
|
591 |
wasBlocked := OperatingSystem blockInterrupts. |
|
592 |
"/ check again - now interrupts are blocked. |
|
593 |
[ |
|
594 |
|p| |
|
595 |
||
596 |
count <= 0 ifTrue:[ |
|
597 |
count := count + 1. |
|
598 |
count == 1 ifTrue:[ |
|
599 |
waitingProcesses notNil ifTrue:[ |
|
600 |
p := self removeFirstWaitingProcess. |
|
601 |
p notNil ifTrue:[ |
|
602 |
Processor resume:p. |
|
603 |
]. |
|
604 |
]. |
|
605 |
]. |
|
606 |
]. |
|
607 |
] ensure:[ |
|
608 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
609 |
] |
|
610 |
] |
|
611 |
||
612 |
"Modified: 28.2.1996 / 21:24:08 / cg" |
|
613 |
! ! |
|
614 |
||
615 |
!Semaphore methodsFor:'testing'! |
|
616 |
||
617 |
isEmpty |
|
618 |
"ST80 compatibility - return true if there are no waiters" |
|
619 |
||
620 |
^ waitingProcesses size == 0 |
|
621 |
||
622 |
"Created: / 3.5.1996 / 18:06:27 / cg" |
|
623 |
"Modified: / 18.6.1998 / 16:07:38 / cg" |
|
1577
720f14f90e2c
access to waitingProcesses added
Claus Gittinger <cg@exept.de>
parents:
1329
diff
changeset
|
624 |
! |
720f14f90e2c
access to waitingProcesses added
Claus Gittinger <cg@exept.de>
parents:
1329
diff
changeset
|
625 |
|
217 | 626 |
wouldBlock |
627 |
"return true, if the receiver would block the activeProcess |
|
6615 | 628 |
if a wait was performed. False otherwise. |
629 |
Attention: if asked without some global lock (blockedInterrupts), |
|
630 |
the returned value may be wrong right away." |
|
217 | 631 |
|
6615 | 632 |
^ count <= 0 |
217 | 633 |
! ! |
634 |
||
8569 | 635 |
!Semaphore methodsFor:'waiting'! |
5713 | 636 |
|
699 | 637 |
critical:aBlock |
638 |
"evaluate aBlock as a critical region; the receiver must be |
|
639 |
created using Semaphore>>forMutualExclusion" |
|
640 |
||
7717
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
641 |
|retVal gotSema wasBlocked| |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
642 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
643 |
"/ inlined common case - ugly kludge but helpful |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
644 |
wasBlocked := OperatingSystem blockInterrupts. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
645 |
count > 0 ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
646 |
count := count - 1. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
647 |
count == 0 ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
648 |
lastOwnerID := Processor activeProcessId. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
649 |
]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
650 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
651 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
652 |
retVal := aBlock ifCurtailed:[ self signal ]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
653 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
654 |
OperatingSystem blockInterrupts. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
655 |
[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
656 |
|p| |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
657 |
|
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
658 |
count := count + 1. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
659 |
waitingProcesses notNil ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
660 |
p := self removeFirstWaitingProcess. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
661 |
p notNil ifTrue:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
662 |
Processor resume:p. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
663 |
]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
664 |
]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
665 |
] ensure:[ |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
666 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
667 |
]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
668 |
^ retVal. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
669 |
]. |
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
670 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
6615 | 671 |
|
672 |
[ |
|
673 |
gotSema := self wait. |
|
674 |
retVal := aBlock value. |
|
6616
70d54ffebc91
valueOnUnwindDo: - ifCurtailed.
Claus Gittinger <cg@exept.de>
parents:
6615
diff
changeset
|
675 |
] ifCurtailed:[ |
6615 | 676 |
"/ be careful - the unwind may occur both while waiting |
677 |
"/ AND while evaluating the block. |
|
678 |
gotSema notNil ifTrue:[self signal]. |
|
679 |
]. |
|
680 |
self signal. |
|
681 |
^ retVal |
|
699 | 682 |
|
683 |
" |
|
684 |
the example below is stupid (it should use a SharedQueue, |
|
685 |
or at least a Queue with critical regions). |
|
686 |
Anyhow, it demonstrates how two processes lock each other |
|
687 |
from accessing coll at the same time |
|
688 |
||
689 |
|sema coll| |
|
690 |
||
691 |
sema := Semaphore forMutualExclusion. |
|
692 |
coll := OrderedCollection new:10. |
|
693 |
||
694 |
[ |
|
3669 | 695 |
1 to:1000 do:[:i | |
696 |
sema critical:[ |
|
697 |
coll addLast:i. |
|
698 |
(Delay forSeconds:0.1) wait. |
|
699 |
] |
|
700 |
] |
|
699 | 701 |
] forkAt:4. |
702 |
||
703 |
[ |
|
3669 | 704 |
1 to:1000 do:[:i | |
705 |
sema critical:[ |
|
706 |
coll removeFirst. |
|
707 |
(Delay forSeconds:0.1) wait. |
|
708 |
] |
|
709 |
] |
|
699 | 710 |
] forkAt:4. |
711 |
" |
|
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
|
712 |
|
3669 | 713 |
"Modified: / 16.4.1996 / 10:00:46 / stefan" |
714 |
"Modified: / 21.7.1998 / 17:45:26 / cg" |
|
699 | 715 |
! |
716 |
||
1 | 717 |
wait |
718 |
"wait for the semaphore" |
|
719 |
||
2142 | 720 |
|activeProcess wasBlocked| |
1 | 721 |
|
6615 | 722 |
wasBlocked := OperatingSystem blockInterrupts. |
723 |
||
724 |
count <= 0 ifTrue:[ |
|
725 |
activeProcess := Processor activeProcess. |
|
726 |
||
727 |
" |
|
728 |
need a while-loop here, since more than one process may |
|
729 |
wait for it and another one may also wake up. |
|
730 |
Thus, the count is not always non-zero after returning from |
|
731 |
suspend. |
|
732 |
" |
|
8569 | 733 |
[ |
6986
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
734 |
self addWaitingProcess:activeProcess. |
6615 | 735 |
" |
736 |
for some more descriptive info in processMonitor ... |
|
737 |
... set the state to #wait (instead of #suspend) |
|
738 |
" |
|
739 |
[ |
|
740 |
activeProcess suspendWithState:#wait |
|
6616
70d54ffebc91
valueOnUnwindDo: - ifCurtailed.
Claus Gittinger <cg@exept.de>
parents:
6615
diff
changeset
|
741 |
] ifCurtailed:[ |
7717
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
742 |
self removeWaitingProcess:activeProcess. |
6615 | 743 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
744 |
]. |
|
8569 | 745 |
self removeWaitingProcess:activeProcess. |
746 |
] doUntil:[count > 0]. |
|
93 | 747 |
]. |
748 |
||
10 | 749 |
count := count - 1. |
2262 | 750 |
count == 0 ifTrue:[ |
3600
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
751 |
lastOwnerID := Processor activeProcessId. |
2262 | 752 |
]. |
93 | 753 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
752
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
754 |
|
3600
6c5629eea51d
give mutual-exclusion semas a distinct default name
Claus Gittinger <cg@exept.de>
parents:
3392
diff
changeset
|
755 |
"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
|
756 |
"Modified: / 17.6.1998 / 15:26:27 / cg" |
10 | 757 |
! |
758 |
||
329 | 759 |
waitUncounted |
760 |
"wait for the semaphore; do not consume the resource |
|
761 |
(i.e. do not count down)" |
|
762 |
||
2142 | 763 |
|activeProcess wasBlocked| |
329 | 764 |
|
6615 | 765 |
count > 0 ifTrue:[ |
6601 | 766 |
^ self |
329 | 767 |
]. |
768 |
||
2142 | 769 |
activeProcess := Processor activeProcess. |
329 | 770 |
|
771 |
wasBlocked := OperatingSystem blockInterrupts. |
|
772 |
" |
|
773 |
need a while-loop here, since more than one process may |
|
774 |
wait for it and another one may also wake up. |
|
775 |
Thus, the count is not always non-zero after returning from |
|
776 |
suspend. |
|
777 |
" |
|
6615 | 778 |
[count <= 0] whileTrue:[ |
6986
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
779 |
self addWaitingProcess:activeProcess. |
6601 | 780 |
" |
781 |
for some more descriptive info in processMonitor ... |
|
782 |
... set the state to #wait (instead of #suspend) |
|
783 |
" |
|
784 |
[ |
|
785 |
activeProcess suspendWithState:#wait |
|
6616
70d54ffebc91
valueOnUnwindDo: - ifCurtailed.
Claus Gittinger <cg@exept.de>
parents:
6615
diff
changeset
|
786 |
] ifCurtailed:[ |
7717
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
787 |
self removeWaitingProcess:activeProcess. |
6601 | 788 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
789 |
]. |
|
8569 | 790 |
self removeWaitingProcess:activeProcess. |
329 | 791 |
]. |
792 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
752
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
793 |
|
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
794 |
"Modified: 13.12.1995 / 13:26:49 / stefan" |
2352 | 795 |
"Modified: 1.2.1997 / 12:11:41 / cg" |
329 | 796 |
! |
797 |
||
159 | 798 |
waitWithTimeout:seconds |
799 |
"wait for the semaphore, but abort the wait after some time. |
|
2690 | 800 |
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
|
801 |
due to a timeout. |
101239898989
unwind block over wait (in critical)
Claus Gittinger <cg@exept.de>
parents:
770
diff
changeset
|
802 |
The seconds-argument may be a float (i.e. use 0.1 for a 100ms timeout). |
2690 | 803 |
With zero timeout, this can be used to poll a semaphore (returning |
804 |
the receiver if the semaphore is available, nil if not). |
|
4902
caf73c9821c5
Allow nil as argument to #waitWithTimeout: (no timeout) (stefan)
Claus Gittinger <cg@exept.de>
parents:
4633
diff
changeset
|
805 |
However, polling is not the intended use of semaphores, though. |
caf73c9821c5
Allow nil as argument to #waitWithTimeout: (no timeout) (stefan)
Claus Gittinger <cg@exept.de>
parents:
4633
diff
changeset
|
806 |
If seconds is nil, wait without timeout." |
159 | 807 |
|
6061
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
808 |
|millis| |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
809 |
|
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
810 |
seconds notNil ifTrue:[ |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
811 |
millis := seconds * 1000 |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
812 |
]. |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
813 |
^ self waitWithTimeoutMs:millis. |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
814 |
! |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
815 |
|
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
816 |
waitWithTimeoutMs:milliSeconds |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
817 |
"wait for the semaphore, but abort the wait after some time. |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
818 |
return the receiver if the semaphore triggered normal, nil if we return |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
819 |
due to a timeout. |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
820 |
With zero timeout, this can be used to poll a semaphore (returning |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
821 |
the receiver if the semaphore is available, nil if not). |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
822 |
However, polling is not the intended use of semaphores, though. |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
823 |
If milliSeconds is nil, wait without timeout." |
9e266783d5c2
care for nil arg in #waitWithTimeout:
Claus Gittinger <cg@exept.de>
parents:
5713
diff
changeset
|
824 |
|
8569 | 825 |
|activeProcess timeoutOccured wasBlocked timeoutBlock now endTime| |
159 | 826 |
|
827 |
wasBlocked := OperatingSystem blockInterrupts. |
|
828 |
||
6615 | 829 |
count <= 0 ifTrue:[ |
8569 | 830 |
"with zero-timeout, this is a poll" |
831 |
milliSeconds == 0 ifTrue:[ |
|
6615 | 832 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
833 |
^ nil |
|
834 |
]. |
|
159 | 835 |
|
6615 | 836 |
activeProcess := Processor activeProcess. |
8569 | 837 |
timeoutOccured := false. |
302 | 838 |
|
6615 | 839 |
milliSeconds notNil ifTrue:[ |
8569 | 840 |
"Wait with timeout: calculate the end-time" |
6615 | 841 |
now := OperatingSystem getMillisecondTime. |
842 |
endTime := OperatingSystem millisecondTimeAdd:now and:milliSeconds. |
|
843 |
||
8569 | 844 |
timeoutBlock := [timeoutOccured := true. timeoutBlock:= nil. Processor resume:activeProcess]. |
845 |
Processor addTimedBlock:timeoutBlock for:activeProcess atMilliseconds:endTime. |
|
4902
caf73c9821c5
Allow nil as argument to #waitWithTimeout: (no timeout) (stefan)
Claus Gittinger <cg@exept.de>
parents:
4633
diff
changeset
|
846 |
]. |
159 | 847 |
|
6615 | 848 |
" |
849 |
need a while-loop here, since more than one process may |
|
850 |
wait for it and another one may also wake up. |
|
851 |
Thus, the count is not always non-zero after returning from |
|
852 |
suspend. |
|
853 |
" |
|
8569 | 854 |
[ |
6986
d2ef4d62861e
Isolate waitProcesses (prepare for sorting by prio)
Stefan Vogel <sv@exept.de>
parents:
6984
diff
changeset
|
855 |
self addWaitingProcess:activeProcess. |
6615 | 856 |
|
857 |
" |
|
858 |
for some more descriptive info in processMonitor ... |
|
859 |
... set the state to #wait (instead of #suspend) |
|
860 |
" |
|
861 |
[ |
|
8569 | 862 |
"sleep until resumed..." |
6615 | 863 |
activeProcess suspendWithState:#wait. |
6616
70d54ffebc91
valueOnUnwindDo: - ifCurtailed.
Claus Gittinger <cg@exept.de>
parents:
6615
diff
changeset
|
864 |
] ifCurtailed:[ |
8569 | 865 |
timeoutBlock notNil ifTrue:[ |
866 |
Processor removeTimedBlock:timeoutBlock. |
|
867 |
timeoutBlock := nil. |
|
868 |
]. |
|
7717
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
869 |
self removeWaitingProcess:activeProcess. |
6615 | 870 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
871 |
]. |
|
872 |
||
7717
ac9f01ef7157
tuning - although ugly, the speedup of critical: is > 30%
Claus Gittinger <cg@exept.de>
parents:
7258
diff
changeset
|
873 |
self removeWaitingProcess:activeProcess. |
6615 | 874 |
timeoutOccured ifTrue:[ |
875 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
|
876 |
^ nil |
|
877 |
]. |
|
8569 | 878 |
] doUntil:[count > 0]. |
4902
caf73c9821c5
Allow nil as argument to #waitWithTimeout: (no timeout) (stefan)
Claus Gittinger <cg@exept.de>
parents:
4633
diff
changeset
|
879 |
|
8569 | 880 |
timeoutBlock notNil ifTrue:[ |
881 |
Processor removeTimedBlock:timeoutBlock. |
|
882 |
timeoutBlock := nil. |
|
6615 | 883 |
]. |
4902
caf73c9821c5
Allow nil as argument to #waitWithTimeout: (no timeout) (stefan)
Claus Gittinger <cg@exept.de>
parents:
4633
diff
changeset
|
884 |
]. |
2690 | 885 |
|
8569 | 886 |
"if we come here, we have accquired the semaphore" |
159 | 887 |
count := count - 1. |
2262 | 888 |
count == 0 ifTrue:[ |
4902
caf73c9821c5
Allow nil as argument to #waitWithTimeout: (no timeout) (stefan)
Claus Gittinger <cg@exept.de>
parents:
4633
diff
changeset
|
889 |
lastOwnerID := Processor activeProcessId. |
2262 | 890 |
]. |
159 | 891 |
wasBlocked ifFalse:[OperatingSystem unblockInterrupts]. |
770
402958905760
protocol of waitWithTImeOut: changed
Claus Gittinger <cg@exept.de>
parents:
769
diff
changeset
|
892 |
^ self |
752
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
893 |
|
0259dd855289
new suspendAction, Semaphore & ProcSched stuff from stefan
Claus Gittinger <cg@exept.de>
parents:
699
diff
changeset
|
894 |
"Modified: 13.12.1995 / 13:27:24 / stefan" |
2690 | 895 |
"Modified: 16.6.1997 / 21:54:38 / cg" |
699 | 896 |
! ! |
77 | 897 |
|
1812
a048a98aa299
kludge around a situation, where one process
Claus Gittinger <cg@exept.de>
parents:
1577
diff
changeset
|
898 |
!Semaphore class methodsFor:'documentation'! |
183 | 899 |
|
699 | 900 |
version |
8569 | 901 |
^ '$Header: /cvs/stx/stx/libbasic/Semaphore.st,v 1.72 2004-09-21 18:06:07 stefan Exp $' |
1 | 902 |
! ! |