SystemWindow instances can't be garbage-collected

First off:
<rant>why do we have an IRC channel if nobody seems to be listening??</rant>

too small community for an irc channel. My experience with irc is that 90-99% of people logged in at least are idle. For its size #pharo is quite active actually.  

sorry can't help you with your question :(

On Sat, Jun 21, 2014 at 6:24 PM, Max Leske <[hidden email]> wrote:

First off:
<rant>why do we have an IRC channel if nobody seems to be listening??</rant>

Sorry about that. Here’s my original question as posted on IRC:

Hi guys.
I have a couple of SystemWindow instances sitting around in my image which can’t be garbage collected. They all once showed a debugger but that debugger seems to be only referenced by the window.
I’m kind of running in circles. Does anyone have an idea how to find the root pointers which prevent garbage collection of an object? Using PointerFinder manually isn’t helping much (I’m in a Pharo 1.1.1 image).

Cheers,
Max

First off:
<rant>why do we have an IRC channel if nobody seems to be listening??</rant>

too small community for an irc channel. My experience with irc is that 90-99% of people logged in at least are idle. For its size #pharo is quite active actually.  

On 21 Jun 2014, at 17:36, kilon alios <[hidden email]> wrote:

First off:
<rant>why do we have an IRC channel if nobody seems to be listening??</rant>

too small community for an irc channel. My experience with irc is that 90-99% of people logged in at least are idle. For its size #pharo is quite active actually.  

I am IRC when at work (and not forgetting to start the IRC client). But often when people ask questions it is exactly the wrong moment in time.

I just *can’t*  instantly drop what I am doing an tend to the IRC channel… I really wonder how people do it… do they really stop their work right in the

miiddle to answer questions? How are they productive? 

Marcus

On 21.06.2014, at 18:53, Marcus Denker <[hidden email]> wrote:

On 21 Jun 2014, at 17:36, kilon alios <[hidden email]> wrote:

First off:
<rant>why do we have an IRC channel if nobody seems to be listening??</rant>

too small community for an irc channel. My experience with irc is that 90-99% of people logged in at least are idle. For its size #pharo is quite active actually.  

I am IRC when at work (and not forgetting to start the IRC client). But often when people ask questions it is exactly the wrong moment in time.

I just *can’t*  instantly drop what I am doing an tend to the IRC channel… I really wonder how people do it… do they really stop their work right in the

miiddle to answer questions? How are they productive? 

I fully agree. I was just momentarily pissed off :)

Marcus

Found the problem, documenting it here in case anybody else ever needs this (remember, this is 1.1.1).

Open a debugger (e.g. by evaluating 1/0), then click into the lower right workspace and type something. OCompletion will now have added an entry to the EventManager actionMap with a ContextVariablesInspector instance as the key. There seems to be a cycle there that can’t be resolved by the garbage collector, since I wasn’t able to find any non weak global pointers (an OContext is referenced by an MessageSend in the action map. The OContext references a morph which is connected to the SystemWindow. Some of those morphs reference the ContextVariablesInspector as their model).

Anyhow, it should be safe to send EventManager>>cleanUp: with argument true (actionMaps and their contents get recreated on demand), which will release those entries and allow the garbage collector to collect the SystemWindows, other morphs and the Debugger instances.

Note that this is probably not an issue in later versions (e.g. 3.0 doesn’t include EventManager anymore) but it might be relevant for later 1.x versions.

Max

On 21.06.2014, at 20:44, Max Leske <[hidden email]> wrote:

On 21.06.2014, at 18:53, Marcus Denker <[hidden email]> wrote:

On 21 Jun 2014, at 17:36, kilon alios <[hidden email]> wrote:

First off:
<rant>why do we have an IRC channel if nobody seems to be listening??</rant>

too small community for an irc channel. My experience with irc is that 90-99% of people logged in at least are idle. For its size #pharo is quite active actually.  

I am IRC when at work (and not forgetting to start the IRC client). But often when people ask questions it is exactly the wrong moment in time.

I just *can’t*  instantly drop what I am doing an tend to the IRC channel… I really wonder how people do it… do they really stop their work right in the

miiddle to answer questions? How are they productive? 

I fully agree. I was just momentarily pissed off :)

Marcus

For documentation purposes, this is what I found to be necessary to really clean all window instances. Note that this only works reliably when invoked from a non-UI process (e.g. via WAKom).

cleanupWindows

"in general: the gabage collector seems to be unable to resolve all circular dependencies with weak pointers.

This forces us to explicitly remove the weak pointers to enable garbage colltection.

It also seems to be a problem to invoke the cleanup from within a UI process (e.g. from a workspace). 

Ergo: 

- when invoked from a workspace not all instances may be garbage collected

- when invoked from a non UI process (e.g. WAKom) all instances should have been collected

- performning a manual garbage collection after having invoked this code from a workspace will

(usually) remove the pending instances (new process context)"

| count |

count := 1.

self

cleanupEvents;

cleanupWorkspaces;

cleanupSystemWindows.

[ Smalltalk garbageCollect. count := count + 1 ] doWhileFalse: [

SystemWindow allSubInstances isEmpty or: [ count > 5 "arbitrary number" ] ]

cleanupWorkspaces

PluggableTextMorph allSubInstances do: [ :each | each  

hasUnacceptedEdits: false;

askBeforeDiscardingEdits: false;

myDependents: nil ]

cleanupSystemWindows

[ [ SystemWindow allSubInstances do: [ :window |

window 

makeClosable;

delete ] ] 

on: Error 

do: [ :ex | 

"may get here because we're trying to delete a window which has been deleted already."

ex return  ].

Smalltalk garbageCollect.

"already deleted but still hanging aroung (also see #cleanupEvents and #cleanupWorkspaces)"

SystemWindow allSubInstances 

select: [ :e | e model isNil and: [ e owner isNil ] ]

thenDo: [ :e |

"clean some known places where references can prevent GC"

UITheme current focusIndicator: nil.

ActiveHand mouseOverHandler initialize.

ActiveHand keyboardFocus: nil.

World cleanseStepList.

"e.g. Workspace has a dependents array wich can point to the window"

(PointerFinder pointersTo: e) do: [ :p | 

p class = DependentsArray ifTrue: [

"the first pointer is the 'main' pointer in about 99% of the cases"

(PointerFinder pointersTo: p) first removeDependent: e ] ] ] 

] on: Error do: [ "ignore” ]

On 21.06.2014, at 23:11, Max Leske <[hidden email]> wrote:

Found the problem, documenting it here in case anybody else ever needs this (remember, this is 1.1.1).

Open a debugger (e.g. by evaluating 1/0), then click into the lower right workspace and type something. OCompletion will now have added an entry to the EventManager actionMap with a ContextVariablesInspector instance as the key. There seems to be a cycle there that can’t be resolved by the garbage collector, since I wasn’t able to find any non weak global pointers (an OContext is referenced by an MessageSend in the action map. The OContext references a morph which is connected to the SystemWindow. Some of those morphs reference the ContextVariablesInspector as their model).

Anyhow, it should be safe to send EventManager>>cleanUp: with argument true (actionMaps and their contents get recreated on demand), which will release those entries and allow the garbage collector to collect the SystemWindows, other morphs and the Debugger instances.

Note that this is probably not an issue in later versions (e.g. 3.0 doesn’t include EventManager anymore) but it might be relevant for later 1.x versions.

Max

On 21.06.2014, at 20:44, Max Leske <[hidden email]> wrote:

On 21.06.2014, at 18:53, Marcus Denker <[hidden email]> wrote:

On 21 Jun 2014, at 17:36, kilon alios <[hidden email]> wrote:

First off:
<rant>why do we have an IRC channel if nobody seems to be listening??</rant>

too small community for an irc channel. My experience with irc is that 90-99% of people logged in at least are idle. For its size #pharo is quite active actually.  

I am IRC when at work (and not forgetting to start the IRC client). But often when people ask questions it is exactly the wrong moment in time.

I just *can’t*  instantly drop what I am doing an tend to the IRC channel… I really wonder how people do it… do they really stop their work right in the

miiddle to answer questions? How are they productive? 

I fully agree. I was just momentarily pissed off :)

Marcus