Levente Uzonyi uploaded a new version of System to project The Trunk:
http://source.squeak.org/trunk/System-ul.253.mcz

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

Name: System-ul.253
Author: ul
Time: 14 February 2010, 9:12:11.268 am
UUID: 7aaed65b-d0e3-0040-8929-0eb0bf8ecf64
Ancestors: System-ar.252

- fix (again): Timer may be already nil in the #ensure: block in MessageTally >> #spyEvery:on: and MessageTally >> #spyAllEvery:on:

=============== Diff against System-ar.252 ===============

Item was changed:
  ----- Method: MessageTally>>spyAllEvery:on: (in category 'initialize-release') -----
  spyAllEvery: millisecs on: aBlock
  	"Create a spy and spy on the given block at the specified rate."
  	"Spy all the system processes"
  
  	| myDelay time0 |
  	(aBlock isMemberOf: BlockClosure)
  		ifFalse: [self error: 'spy needs a block here'].
  	self class: aBlock receiver class method: aBlock method.
  		"set up the probe"
  	myDelay := Delay forMilliseconds: millisecs.
  	time0 := Time millisecondClockValue.
  	gcStats := SmalltalkImage current getVMParameters.
  	Timer ifNotNil: [ Timer terminate ].
  	Timer := [
  		[true] whileTrue: [
  			| observedProcess startTime |
  			startTime := Time millisecondClockValue.
  			myDelay wait.
  			observedProcess := Processor preemptedProcess.
  			self
  				tally: observedProcess suspendedContext
  				in: observedProcess
  				"tally can be > 1 if ran a long primitive"
  				by: (Time millisecondClockValue - startTime) // millisecs].
  		nil] newProcess.
  	Timer priority: Processor timingPriority-1.
  		"activate the probe and evaluate the block"
  	Timer resume.
  	^ aBlock ensure: [
  		"Collect gc statistics"
  		SmalltalkImage current getVMParameters keysAndValuesDo: [ :idx :gcVal | 
  			gcStats at: idx put: (gcVal - (gcStats at: idx))].
  		"cancel the probe and return the value"
+ 		Timer ifNotNil: [
+ 			Timer terminate.
+ 			Timer := nil ].
- 		Timer terminate.
- 		Timer := nil.
  		time := Time millisecondClockValue - time0]!

Item was changed:
  ----- Method: MessageTally>>spyEvery:on: (in category 'initialize-release') -----
  spyEvery: millisecs on: aBlock
  	"Create a spy and spy on the given block at the specified rate."
  	"Spy only on the active process (in which aBlock is run)"
  
  	| myDelay time0 observedProcess |
  	(aBlock isMemberOf: BlockClosure)
  		ifFalse: [self error: 'spy needs a block here'].
  	self class: aBlock receiver class method: aBlock method.
  		"set up the probe"
  	observedProcess := Processor activeProcess.
  	myDelay := Delay forMilliseconds: millisecs.
  	time0 := Time millisecondClockValue.
  	gcStats := SmalltalkImage current getVMParameters.
  	Timer ifNotNil: [ Timer terminate ].
  	Timer := [ 
  		[true] whileTrue: [
  			| startTime |
  			startTime := Time millisecondClockValue.
  			myDelay wait.
  			self
  				tally: Processor preemptedProcess suspendedContext
  				in: (observedProcess == Processor preemptedProcess ifTrue: [observedProcess] ifFalse: [nil])
  				"tally can be > 1 if ran a long primitive"
  				by: (Time millisecondClockValue - startTime) // millisecs].
  		nil] newProcess.
  	Timer priority: Processor timingPriority-1.
  		"activate the probe and evaluate the block"
  	Timer resume.
  	^ aBlock ensure: [
  		"Collect gc statistics"
  		SmalltalkImage current getVMParameters keysAndValuesDo: [ :idx :gcVal | 
  			gcStats at: idx put: (gcVal - (gcStats at: idx))].
  		"cancel the probe and return the value"
+ 		Timer ifNotNil: [
+ 			Timer terminate.
+ 			Timer := nil ].
- 		Timer terminate.
- 		Timer := nil.
  		time := Time millisecondClockValue - time0]!