"

 COPYRIGHT (c) 1992 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 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.

"

Link subclass:#Process

	 instanceVariableNames:'id prio state startBlock name 

				restartable interruptActions 

				exitAction exitSemaphore suspendSemaphore 

				singleStepping emergencySignalHandler'

	 classVariableNames:'TerminateSignal'

	 poolDictionaries:''

	 category:'Kernel-Processes'

!

Process comment:'

COPYRIGHT (c) 1992 by Claus Gittinger

	     All Rights Reserved

'!

!Process class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1992 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 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

"

"

!

documentation

"

    Instances of Process represent lightweight smalltalk processes 

    (i.e. threads). These all run in a shared smalltalk/X address space,

    and can thus access and communicate via any objects.

    Do not confuse these with (heavy-weight) unix processes, which are

    created differently, and do NOT run in the same address space.

    Also notice, that heavy-weight process creation takes much longer.

    (see OperatingSystemclass>>fork).

    Processes are typically created by sending #fork or #forkAt: to a block;

    the block creates a new process, defines itself as its startBlock,

    and (optionally) tells the Processor about the new process.

    Scheduling is done by Processor, which is the sole instance of 

    ProcessorScheduler.

    Processes can be terminated either soft or via a hardTerminate.

    A soft terminate (see Process>>terminate) will raise a TerminationSignal

    in the process, which can be handled by the process. 

    If no other handler was specified, the processes own handler 

    (see Process>>start) will catch the signal and terminate the process. 

    During this signal processing, normal unwind processing takes place,

    this means that with a soft terminate, all valueOnUnwind:/valueNowOrOnUnwind: 

    cleanup blocks are evaluated.

    (so a process which has set up those blocks correctly does not have to

     care especially about cleanup in case of termination).

    Other than that, the TerminateSignal can be cought for special cleanup or

    even to make the process continue execution.

    A hard terminate (Process>>terminateNoSignal) will NOT do all of the above,

    but quickly (and without any cleanup) terminate the process.

    The debugger offers a quickTerminate option on its popupMenu for

    situations, when soft termination fails. (for example, if some error was

    coded into a handler or unwind block).

    Notice: 

	in Smalltalk/X, processes are gone, when an image is restarted;

	this means, that you have to take care of process re-creation yourself.

	Usually, this is done by depending on ObjectMemory, recreating the

	process(s) when the #returnFromSnapshot-change notifiction arrives.

	All views (actually windowGroups) recreate their window process

	on image-restart. You have to do so manually for your own processes.

    A later version will allow specification of automatic restart, but

    thats not yet implemented. However, even when implemented, restartable processes

    will be recreated to restart from the beginning. It will not be possible to

    automatically continue a processes execution where it left off.

    This is a consequence of the portable implementation of ST/X, since in order to

    implement this feature, the machines stack had to be preserved and recreated.

    Although this is possible theoretically, this has not been implemented, since 

    the machines stack layout is highly machine/compiler dependent,

    Process synchronization:

	any other process can wait for a process to suspend or terminate. This

	is implemented by using suspendSemaphore and exitSemaphore, which are 

	signalled when these events occur (see waitUntilSuspended/waitUntilTerminated).

    Instance variables:

	id                     <SmallInteger>   a unique process-id

	prio                   <SmallInteger>   the processes priority

	state                  <Symbol>         the processes state

						(for process-monitor)

	startBlock             <Block>          the startup-block (the one that forked)

	name                   <String-or-nil>  the processes name (if any)

						(for process-monitor)

	suspendSemaphore       <Semaphore>      triggered when suspend (if nonNil)

	exitSemaphore          <Semaphore>      triggered when terminated (if nonNil)

	restartable            <Boolean>        is restartable (not yet implemented)

	interruptActions       <Collection>     interrupt actions as defined by interruptWith:,

						performed at interrupt time

	exitAction             <Block>          additional cleanup action to perform 

						on termination (if nonNil)

	emergencySignalHandler <Block>          can be used for per-process

						emergency signal handling

    Class variables:

	TerminateSignal         <Signal>        signal used to terminate processes

						(should not be cought - or at least

						 rejected in handlers)

"

!

examples 

"

    start a background process, computing 1000 factorial 100 times;

    the processes priority is set to not disturb any interactive process.

    Since its prio is higher than the 3D animation demos prio, you will notice,

    that those are suspended while the computation runs. But Interactive views

    (like browsers) will continue to react normal.

    [

       'starting' printNL.

       100 timesRepeat:[1000 factorial].

       'done with factorial' printNL.

    ] forkAt:(Processor userBackgroundPriority).

    start a background process, computing 1000 factorial 100 times;

    the processes priority is set to not disturb any process.

    The prio is set to 1 (which is the lowest possible) notice that now,

    the 3D animation demos also continue to run. 

    [

       'starting' printNL.

       100 timesRepeat:[1000 factorial].

       'done with factorial' printNL.

    ] forkAt:1.

    start a background process, reading a pipe without blocking other

    processes;

    [

       |p|

       'starting' printNL.

       p := PipeStream readingFrom:'ls -lR .'.

       [p atEnd] whileFalse:[

	   p readWait.

	   p nextLine printNL.

       ].

       p close.

       'done with pipe' printNL.

    ] forkAt:1.

    see more examples in doc/coding 

    (or search in the browser for senders of fork*)

"

! !

!Process class methodsFor:'initialization'!

initialize

    TerminateSignal isNil ifTrue:[

	TerminateSignal := Signal new mayProceed:true.

	TerminateSignal nameClass:self message:#terminateSignal.

	TerminateSignal notifierString:'unhandled process termination'.

    ]

! !

!Process class methodsFor:'signal access'!

terminateSignal

    "return the signal used for process termination"

    ^ TerminateSignal

! !

!Process class methodsFor:'instance creation'!

for:aBlock priority:aPrio

    "create a new (unscheduled) process which will execute aBlock at

     a given priority, once scheduled. The process will start execution once

     it gets a #resume-message."

    ^ self new for:aBlock priority:aPrio

! !

!Process methodsFor:'private'!

for:aBlock priority:aPrio

    "setup the new process - the receiver is not scheduled for

     execution, to get it running, send it #resume"

    |nm|

    prio := aPrio.

    startBlock := aBlock.

    (Processor newProcessFor:self) ifFalse:[ 

	"for some reason, the Processor was unable to create

	 a VM process for me ...."

	^ nil

    ].

    "

     give me a user-friendly name

    "

    (nm := Processor activeProcess name) notNil ifTrue:[

	"

	 avoid name inflation

	"

	(nm endsWith:'(sub)') ifFalse:[

	    nm := nm , ' (sub)'

	].

	name := nm

    ]

! !

!Process methodsFor:'accessing'!

state

    "return a symbol describing the processes state"

    ^ state

!

state:aSymbol

    "set the state - only to be used from scheduler"

    state := aSymbol

!

isDead

    "return true, if the receiver has already terminated"

    ^ state == #dead

!

startBlock

    "return the processes startup-block"

    ^ startBlock

!

emergencySignalHandler:aOneArgBlock

    "set the emergencySignalHandler block.

     See Signal>>documentation for more info."

    emergencySignalHandler := aOneArgBlock

!

emergencySignalHandler

    "return the emergencySignalHandler block.

     See Signal>>documentation for more info."

    ^ emergencySignalHandler

!

priority

    "return the receivers priority"

    ^ prio

!

priority:aNumber

    "set my priority"

    Processor changePriority:aNumber for:self.

!

changePriority:aNumber

    "same as priority:, but returns the old priority.

     (cannot do this in priority: for ST-80 compatibility)"

    |oldPrio|

    oldPrio := prio.

    Processor changePriority:aNumber for:self.

    ^ oldPrio

!

isSingleStepping

    ^ singleStepping

!

singleStep:aBoolean

    singleStepping := aBoolean

!

id

    "return the processes id"

    ^ id

!

name

    "return the processes name"

    ^ name

!

name:aString

    "set the processes name"

    name := aString

!

nameOrId

    "return a string to identify the process - either name or id"

    name notNil ifTrue:[^ name].

    ^ id printString

!

exitAction

    "return the processes exit action"

    ^ exitAction

!

exitAction:aBlock

    "set the processes exit action to aBlock.

     This will be evaluated right before the process dies."

    exitAction := aBlock

!

suspendedContext

    "return the processes suspended context 

     - this is the context from which a process switch into the scheduler

     or another process occured.

     Typically, only the debugger is interrested in this one."

%{  /* NOCONTEXT */

    extern OBJ __threadContext();

    OBJ i;

	RETURN (__threadContext(_intVal(i)));

    }

%}.

    ^ nil

!

maximumStackSize

    "returns the processes stack limit - i.e. the process will be 

     interrupted with a recursionSignal-raise, if it ever

     needs more stack (in bytes) than this number"

%{  /* NOCONTEXT */

    extern int __threadMaxStackSize();

    OBJ i;

	RETURN( _MKSMALLINT(__threadMaxStackSize(_intVal(i))) );

    }

%}.

    ^ nil

!

setMaximumStackSize:limit

    "sets the processes stack limit - i.e. the process will be

     interrupted with a recursionSignal-raise, if it ever

     needs more stack (in bytes) than this number.

     Returns the old value."

%{  /* NOCONTEXT */

    extern int __threadSetMaxStackSize();

    OBJ i;

	RETURN ( _MKSMALLINT(__threadSetMaxStackSize(_intVal(i), _intVal(limit))) );

    }

%}.

    ^ nil

! !

!Process methodsFor:'monitoring'!

usedStackSize

    "Return the processes current stack size.

     This method is for monitoring purposes only - it may vanish."

%{  /* NOCONTEXT */

    extern int __threadUsedStackSize();

    OBJ i;

	RETURN( _MKSMALLINT(__threadUsedStackSize(_intVal(i))) );

    }

%}.

    ^ nil

!

totalStackSize

    "return the processes maximum used stack size.

     This method is for monitoring purposes only - it may vanish."

%{  /* NOCONTEXT */

    extern int __threadTotalStackSize();

    OBJ i;

	RETURN( _MKSMALLINT(__threadTotalStackSize(_intVal(i))) );

    }

%}.

    ^ nil

!

numberOfStackSegments

    "return the processes number of stack segments currently used.

     This method is for monitoring purposes only - it may vanish."

%{  /* NOCONTEXT */

    extern int __threadTotalStackSize();

    OBJ i;

	RETURN( _MKSMALLINT(__threadStackSegments(_intVal(i))) );

    }

%}.

    ^ nil

! !

!Process methodsFor:'private scheduler access'!

setPriority:aNumber

    "set priority without telling processor - not for public use"

    prio := aNumber

!

setStartBlock:aBlock

    "set the receivers startup block"

    startBlock := aBlock

!

setStateTo:newState if:oldState

    state == oldState ifTrue:[state := newState]

!

setStateTo:newState if:oldState1 or:oldState2

    (state == oldState1 or:[state == oldState2]) ifTrue:[state := newState]

!

setId:idNumber state:stateSymbol

    "set id and state - not for public use"

    id := idNumber.

    state := stateSymbol.

! !