A new version of Kernel was added to project The Inbox:
http://source.squeak.org/inbox/Kernel-jar.1384.mcz

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

Name: Kernel-jar.1384
Author: jar
Time: 31 March 2021, 11:11:51.005212 pm
UUID: 7fa9b545-e341-054f-835a-c1bd059fd414
Ancestors: Kernel-mt.1383

Fixes current implementation ignoring some nested  unwind blocks in common situations. Explained and documented in http://forum.world.st/Another-bug-in-Process-terminate-in-unwinding-contexts-tp5128171p5128178.html

A test follows.

=============== Diff against Kernel-mt.1383 ===============

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 outerMost |
- 	| 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]].
  		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].
  
  	"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;
+ 		if there are multiple such nested unwind blocks, try to complete the outer-most block 
+ 		(i.e. the one closest to the bottom of the stack)"
+ 		ctxt := suspendedContext.
+ 		[(ctxt := ctxt findNextUnwindContextUpTo: nil) isNil] whileFalse: 
+ 			"contexts under evaluation have already set their complete (tempAt: 2) to true"
+ 			[(ctxt tempAt:2) ifNotNil: [outerMost := ctxt]].
+ 		outerMost ifNotNil: [
+ 			"This is the outer-most unwind context currently under evaluation;
+ 			let's find an inner context executing outerMost's argument block (tempAt: 1)"
+ 			(suspendedContext findContextSuchThat: [:ctx | 
+ 				ctx closure == (outerMost tempAt: 1)]) ifNotNil: [:inner | 
+ 					suspendedContext runUntilErrorOrReturnFrom: inner.
+ 					"update receiver's suspendedContext reset in the previous step"
+ 					suspendedContext := outerMost]]. 
- 		"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 debugWithTitle: 'Unwind error during termination' translated full: false].
  		"Set the context to its endPC for the benefit of isTerminated."
  		ctxt pc: ctxt endPC]!