The Trunk: Kernel-eem.1185.mcz

Eliot Miranda uploaded a new version of Kernel to project The Trunk:
http://source.squeak.org/trunk/Kernel-eem.1185.mcz

==================== Summary ====================

Name: Kernel-eem.1185
Author: eem
Time: 27 July 2018, 11:08:12.641836 am
UUID: 7296ad00-708d-4cef-b6bc-ceb24d897a70
Ancestors: Kernel-eem.1184

In releaseCriticalSection: use isUnwindContext instead of the more fragile context selector == #ensure:.  Now it will handle ifCurtailed: too.  Thanks Tobias!

Reformat Process>>#terminate.  It was baaad.

=============== Diff against Kernel-eem.1184 ===============

Item was changed:
  ----- Method: Process>>releaseCriticalSection: (in category 'private') -----
  releaseCriticalSection: runnable
  "Figure out if we are terminating a process that is in the ensure: block of a critical section.
  In this case, if the block has made progress, pop the suspendedContext so that we leave the
  ensure: block inside the critical: without signaling the semaphore/exiting the primitive section,
  since presumably this has already happened.  But if it hasn't made progress but is beyond the
+ wait (which we can tell by the oldList being one of the runnable lists, i.e. a LinkedList, not a
- wait (which we can tell my the oldList being one of the runnable lists, i.e. a LinkedList, not a
  Semaphore or Mutex, et al), then the ensure: block needs to be run."
  | selectorJustSent |
  (suspendedContext method pragmaAt: #criticalSection) ifNil: [^self].
  selectorJustSent := suspendedContext selectorJustSentOrSelf.
 
  "Receiver and/or argument blocks of ensure: in Semaphore>>critical: or Mutex>>#critical:"
  suspendedContext isClosureContext ifTrue:
+ [suspendedContext sender isUnwindContext ifTrue:
- [suspendedContext sender selector == #ensure: ifTrue:
  [| notWaitingButMadeNoProgress |
  "Avoid running the ensure: block twice, popping it if it has already been run. If runnable
  but at the wait, leave it in place. N.B. No need to check if the block receiver of ensure: has
  not started to run (via suspendedContext pc = suspendedContext startpc) because ensure:
  uses valueNoContextSwitch, and so there is no suspension point before the wait."
  notWaitingButMadeNoProgress :=
  runnable
  and: [selectorJustSent == #wait
  and: [suspendedContext sender selectorJustSentOrSelf == #valueNoContextSwitch]].
  notWaitingButMadeNoProgress ifFalse:
  [suspendedContext := suspendedContext home]].
  ^self].
 
  "Either Semaphore>>critical: or Mutex>>#critical:.  Is the process still blocked?  If so, nothing further to do."
  runnable ifFalse: [^self].
 
  "If still at the wait the ensure: block has not been activated, so signal to restore."
  selectorJustSent == #wait ifTrue:
  [suspendedContext receiver signal].
 
  "If still at the lock primitive and the lock primitive just acquired ownership (indicated by it answering false)
  then the ensure block has not been activated, so explicitly primitiveExitCriticalSection to unlock."
  (selectorJustSent == #primitiveEnterCriticalSection
  or: [selectorJustSent == #primitiveTestAndSetOwnershipOfCriticalSection]) ifTrue:
  [(suspendedContext stackPtr > 0
   and: [suspendedContext top == false]) ifTrue:
  [suspendedContext receiver primitiveExitCriticalSection]]!

Item was changed:
  ----- Method: Process>>terminate (in category 'changing process state') -----
  terminate
  "Stop the process that the receiver represents forever.
  Unwind to execute pending ensure:/ifCurtailed: blocks before terminating.
  If the process is in the middle of a critical: critical section, release it properly."
 
  | ctxt unwindBlock oldList |
+ self isActiveProcess ifTrue:
+ [ctxt := thisContext.
+ [ctxt := ctxt findNextUnwindContextUpTo: nil.
+  ctxt ~~ nil] whileTrue:
+ [(ctxt tempAt: 2) ifNil:
+ ["N.B. Unlike Context>>unwindTo: we do not set complete (tempAt: 2) to true."
+ unwindBlock := ctxt tempAt: 1.
+ thisContext terminateTo: ctxt.
+ unwindBlock value]].
- self isActiveProcess ifTrue: [
- ctxt := thisContext.
- [ ctxt := ctxt findNextUnwindContextUpTo: nil.
- ctxt isNil
- ] whileFalse: [
- (ctxt tempAt: 2) ifNil:[
- ctxt tempAt: 2 put: nil.
- unwindBlock := ctxt tempAt: 1.
- thisContext terminateTo: ctxt.
- unwindBlock value].
- ].
  thisContext terminateTo: nil.
  self suspend.
+ "If the process is resumed this will provoke a cannotReturn: error.
+ Would self debug: thisContext title: 'Resuming a terminated process' be better?"
+ ^self].
- ] ifFalse:[
- "Always suspend the process first so it doesn't accidentally get woken up.
- N.B. If oldList is a LinkedList then the process is runnable. If it is a Semaphore/Mutex et al
- then the process is blocked, and if it is nil then the process is already suspended."
- oldList := self suspend.
- suspendedContext ifNotNil:
- ["Release any method marked with the <criticalSection> pragma.
-  The argument is whether the process is runnable."
- self releaseCriticalSection: (oldList isNil or: [oldList class == LinkedList]).
 
+ "Always suspend the process first so it doesn't accidentally get woken up.
+ N.B. If oldList is a LinkedList then the process is runnable. If it is a Semaphore/Mutex et al
+ then the process is blocked, and if it is nil then the process is already suspended."
+ oldList := self suspend.
+ suspendedContext ifNotNil:
+ ["Release any method marked with the <criticalSection> pragma.
+  The argument is whether the process is runnable."
+ self releaseCriticalSection: (oldList isNil or: [oldList class == LinkedList]).
- "If terminating a process halfways through an unwind, try to complete that unwind block first."
- (suspendedContext findNextUnwindContextUpTo: nil) ifNotNil:
- [:outer|
- (suspendedContext findContextSuchThat:[:c| c closure == (outer tempAt: 1)]) ifNotNil:
- [:inner| "This is an unwind block currently under evaluation"
- suspendedContext runUntilErrorOrReturnFrom: inner]].
 
+ "If terminating a process halfways through an unwind, try to complete that unwind block first."
+ (suspendedContext findNextUnwindContextUpTo: nil) ifNotNil:
+ [:outer|
+ (suspendedContext findContextSuchThat:[:c| c closure == (outer tempAt: 1)]) ifNotNil:
+ [:inner| "This is an unwind block currently under evaluation"
+ suspendedContext runUntilErrorOrReturnFrom: inner]].
+
+ ctxt := self popTo: suspendedContext bottomContext.
+ ctxt == suspendedContext bottomContext ifFalse:
+ [self debug: ctxt title: 'Unwind error during termination'].
+ "Set the context to its endPC for the benefit of isTerminated."
+ ctxt pc: ctxt endPC]!
- ctxt := self popTo: suspendedContext bottomContext.
- ctxt == suspendedContext bottomContext ifFalse:
- [self debug: ctxt title: 'Unwind error during termination'].
- "Set the context to its endPC for the benefit of isTerminated."
- ctxt pc: ctxt endPC]]!