hg/stx-libbasic: comparison Semaphore.st

equal deleted inserted replaced

-:04533375e12c
+:12f456343eea
 Object subclass:#Semaphore
 	 instanceVariableNames:'count waitingProcesses'
 	 classVariableNames:''
 	 poolDictionaries:''
-	 category:'Kernel-Processes'!
+	 category:'Kernel-Processes'
+!
 !Semaphore class methodsFor:'documentation'!
 copyright
 "
 inclusion of the above copyright notice.   This software may not
 be provided or otherwise made available to, or used by, any
 other person.  No title to or ownership of the software is
 hereby transferred.
 "
-!
-version
-^ '$Header: /cvs/stx/stx/libbasic/Semaphore.st,v 1.23 1995-11-15 14:22:56 werner Exp $'
 !
 documentation
 "
 Semaphores are used to synchronize processes providing a nonBusy wait
 "
 ! !
 !Semaphore class methodsFor:'instance creation'!
+forMutualExclusion
+"create & return a new semaphore which allows exactly one process to
+wait on it without blocking"
+^ super new setCount:1
+!
 new
 "create & return a new semaphore which blocks until a signal is sent"
 ^ super new setCount:0
 !
 new:n
 "create & return a new semaphore which allows n waits before
 blocking"
 ^ super new setCount:n
-!
+! !
-forMutualExclusion
+!Semaphore methodsFor:'printing & storing'!
-"create & return a new semaphore which allows exactly one process to
-wait on it without blocking"
+displayString
+^ self class name , '(' , count printString , ')'
-^ super new setCount:1
 ! !
 !Semaphore methodsFor:'private accessing'!
 setCount:n
 if a wait was performed. False otherwise."
 ^ count == 0
 ! !
-!Semaphore methodsFor:'printing & storing'!
-displayString
-^ self class name , '(' , count printString , ')'
-! !
 !Semaphore methodsFor:'wait & signal'!
-wait
-"wait for the semaphore"
-|current wasBlocked|
-"
-this works only since interrupts are only serviced at
-message send and method-return time ....
-If you add a message send into the ifTrue:-block, things will
-go mad ... (especially be careful when adding a debugPrint-here)
-"
-count ~~ 0 ifTrue:[
-	count := count - 1.
-	^ self
-].
-current := Processor activeProcess.
-wasBlocked := OperatingSystem blockInterrupts.
-"
-need a while-loop here, since more than one process may
-wait for it and another one may also wake up.
-Thus, the count is not always non-zero after returning from
-suspend.
-"
-[count == 0] whileTrue:[
-	waitingProcesses add:current.
-	"
-	 for some more descriptive info in processMonitor ...
-	 (notice that state could already be #ioWait, #timeWait or anything else)
-	"
-	current setStateTo:#wait if:#active.
-	Processor suspend:current
-].
-count := count - 1.
-wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
-!
-waitUncounted
-"wait for the semaphore; do not consume the resource
-(i.e. do not count down)"
-|current wasBlocked|
-"
-this works only since interrupts are only serviced at
-message send and method-return time ....
-If you add a message send into the ifTrue:-block, things will
-go mad ... (especially be careful when adding a debugPrint-here)
-"
-count ~~ 0 ifTrue:[
-	^ self
-].
-current := Processor activeProcess.
-wasBlocked := OperatingSystem blockInterrupts.
-"
-need a while-loop here, since more than one process may
-wait for it and another one may also wake up.
-Thus, the count is not always non-zero after returning from
-suspend.
-"
-[count == 0] whileTrue:[
-	waitingProcesses add:current.
-	"
-	 for some more descriptive info in processMonitor ...
-	 (notice that state could already be #ioWait, #timeWait or anything else)
-	"
-	current setStateTo:#wait if:#active.
-	Processor suspend:current
-].
-wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
-!
-waitWithTimeout:seconds
-"wait for the semaphore, but abort the wait after some time.
-return true if semaphore triggered normal, false if we return
-due to a timeout. With zero timeout, this can be used to poll
-a semaphore (which is not the intend of semaphores, though)."
-|current timeoutOccured wasBlocked unblock now endTime|
-"
-this works only since interrupts are only serviced at
-message send and method-return time ....
-If you add a message send into the ifTrue:-block, things will
-go mad ... (especially be careful when adding a debugPrint-here)
-"
-count ~~ 0 ifTrue:[
-	count := count - 1.
-	^ true
-].
-"
-with zero-timeout, this is a poll
-"
-seconds = 0 ifTrue:[
-	^ false
-].
-current := Processor activeProcess.
-wasBlocked := OperatingSystem blockInterrupts.
-"
-calculate the end-time
-"
-now := OperatingSystem getMillisecondTime.
-endTime := OperatingSystem millisecondTimeAdd:now and:(seconds * 1000).
-unblock := [timeoutOccured := true. Processor resume:current].
-Processor addTimedBlock:unblock for:current atMilliseconds:endTime.
-"
-need a while-loop here, since more than one process may
-wait for it and another one may also wake up.
-Thus, the count is not always non-zero after returning from
-suspend.
-"
-[count == 0] whileTrue:[
-	waitingProcesses add:current.
-	"
-	 for some more descriptive info in processMonitor ...
-	 (notice that state could already be #ioWait or #timeWait)
-	"
-	current setStateTo:#wait if:#active.
-	timeoutOccured := false.
-	Processor suspend:current.
-	timeoutOccured ifTrue:[
-	    waitingProcesses remove:current ifAbsent:[].
-	    wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
-	    ^ false
-	].
-].
-Processor removeTimedBlock:unblock.
-count := count - 1.
-wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
-^ true
-!
-signalOnce
-"wakeup waiters - but only once.
-I.e. if the semaphore has already been signalled, this
-is ignored."
-|wasBlocked|
-count == 0 ifTrue:[
-	wasBlocked := OperatingSystem blockInterrupts.
-	count == 0 ifTrue:[
-	    self signal
-	].
-	wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
-]
-!
-signal
-"waking up (first) waiter"
-|p wasBlocked|
-wasBlocked := OperatingSystem blockInterrupts.
-count := count + 1.
-waitingProcesses notEmpty ifTrue:[
-	p := waitingProcesses removeFirst.
-	p resume.
-].
-wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
-!
-signalIf
-"signal the semaphore, but only if being waited upon.
-This can be used for one-shot semaphores (i.e. not remembering
-previous signals)"
-|wasBlocked|
-waitingProcesses notEmpty ifTrue:[
-	wasBlocked := OperatingSystem blockInterrupts.
-	waitingProcesses notEmpty ifTrue:[
-	    self signal
-	].
-	wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
-]
-!
-signalForAll
-"signal the semaphore for all waiters.
-This can be used for process synchronization, if multiple processes are
-waiting for a common event."
-|wasBlocked|
-[waitingProcesses notEmpty] whileTrue:[
-	wasBlocked := OperatingSystem blockInterrupts.
-	waitingProcesses notEmpty ifTrue:[
-	    self signal
-	].
-	wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
-]
-!
 critical:aBlock
 "evaluate aBlock as a critical region; the receiver must be
 created using Semaphore>>forMutualExclusion"
 		(Delay forSeconds:0.1) wait.
 	    ]
 	]
 ] forkAt:4.
 "
-! !
+!
+signal
+"waking up (first) waiter"
+|p wasBlocked|
+wasBlocked := OperatingSystem blockInterrupts.
+count := count + 1.
+waitingProcesses notEmpty ifTrue:[
+	p := waitingProcesses removeFirst.
+	p resume.
+].
+wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
+!
+signalForAll
+"signal the semaphore for all waiters.
+This can be used for process synchronization, if multiple processes are
+waiting for a common event."
+|wasBlocked|
+[waitingProcesses notEmpty] whileTrue:[
+	wasBlocked := OperatingSystem blockInterrupts.
+	waitingProcesses notEmpty ifTrue:[
+	    self signal
+	].
+	wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
+]
+!
+signalIf
+"signal the semaphore, but only if being waited upon.
+This can be used for one-shot semaphores (i.e. not remembering
+previous signals)"
+|wasBlocked|
+waitingProcesses notEmpty ifTrue:[
+	wasBlocked := OperatingSystem blockInterrupts.
+	waitingProcesses notEmpty ifTrue:[
+	    self signal
+	].
+	wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
+]
+!
+signalOnce
+"wakeup waiters - but only once.
+I.e. if the semaphore has already been signalled, this
+is ignored."
+|wasBlocked|
+count == 0 ifTrue:[
+	wasBlocked := OperatingSystem blockInterrupts.
+	count == 0 ifTrue:[
+	    self signal
+	].
+	wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
+]
+!
+wait
+"wait for the semaphore"
+|current wasBlocked|
+"
+this works only since interrupts are only serviced at
+message send and method-return time ....
+If you add a message send into the ifTrue:-block, things will
+go mad ... (especially be careful when adding a debugPrint-here)
+"
+count ~~ 0 ifTrue:[
+	count := count - 1.
+	^ self
+].
+current := Processor activeProcess.
+wasBlocked := OperatingSystem blockInterrupts.
+"
+need a while-loop here, since more than one process may
+wait for it and another one may also wake up.
+Thus, the count is not always non-zero after returning from
+suspend.
+"
+[count == 0] whileTrue:[
+	waitingProcesses add:current.
+	"
+	 for some more descriptive info in processMonitor ...
+	 (notice that state could already be #ioWait, #timeWait or anything else)
+	"
+	current setStateTo:#wait if:#active.
+	Processor suspend:current
+].
+count := count - 1.
+wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
+!
+waitUncounted
+"wait for the semaphore; do not consume the resource
+(i.e. do not count down)"
+|current wasBlocked|
+"
+this works only since interrupts are only serviced at
+message send and method-return time ....
+If you add a message send into the ifTrue:-block, things will
+go mad ... (especially be careful when adding a debugPrint-here)
+"
+count ~~ 0 ifTrue:[
+	^ self
+].
+current := Processor activeProcess.
+wasBlocked := OperatingSystem blockInterrupts.
+"
+need a while-loop here, since more than one process may
+wait for it and another one may also wake up.
+Thus, the count is not always non-zero after returning from
+suspend.
+"
+[count == 0] whileTrue:[
+	waitingProcesses add:current.
+	"
+	 for some more descriptive info in processMonitor ...
+	 (notice that state could already be #ioWait, #timeWait or anything else)
+	"
+	current setStateTo:#wait if:#active.
+	Processor suspend:current
+].
+wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
+!
+waitWithTimeout:seconds
+"wait for the semaphore, but abort the wait after some time.
+return true if semaphore triggered normal, false if we return
+due to a timeout. With zero timeout, this can be used to poll
+a semaphore (which is not the intend of semaphores, though)."
+|current timeoutOccured wasBlocked unblock now endTime|
+"
+this works only since interrupts are only serviced at
+message send and method-return time ....
+If you add a message send into the ifTrue:-block, things will
+go mad ... (especially be careful when adding a debugPrint-here)
+"
+count ~~ 0 ifTrue:[
+	count := count - 1.
+	^ true
+].
+"
+with zero-timeout, this is a poll
+"
+seconds = 0 ifTrue:[
+	^ false
+].
+current := Processor activeProcess.
+wasBlocked := OperatingSystem blockInterrupts.
+"
+calculate the end-time
+"
+now := OperatingSystem getMillisecondTime.
+endTime := OperatingSystem millisecondTimeAdd:now and:(seconds * 1000).
+unblock := [timeoutOccured := true. Processor resume:current].
+Processor addTimedBlock:unblock for:current atMilliseconds:endTime.
+"
+need a while-loop here, since more than one process may
+wait for it and another one may also wake up.
+Thus, the count is not always non-zero after returning from
+suspend.
+"
+[count == 0] whileTrue:[
+	waitingProcesses add:current.
+	"
+	 for some more descriptive info in processMonitor ...
+	 (notice that state could already be #ioWait or #timeWait)
+	"
+	current setStateTo:#wait if:#active.
+	timeoutOccured := false.
+	Processor suspend:current.
+	timeoutOccured ifTrue:[
+	    waitingProcesses remove:current ifAbsent:[].
+	    wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
+	    ^ false
+	].
+].
+Processor removeTimedBlock:unblock.
+count := count - 1.
+wasBlocked ifFalse:[OperatingSystem unblockInterrupts].
+^ true
+! !
+!Semaphore class methodsFor:'documentation'!
+version
+^ '$Header: /cvs/stx/stx/libbasic/Semaphore.st,v 1.24 1995-12-07 21:30:36 cg Exp $'
+! !

changeset 699	12f456343eea
parent 560	ecb5857b60cc
child 752	0259dd855289