Re: Stack Overflow

Hi everybody!

I recently ran into the same problem that was reported by Thomas
at the beginning of this year.

I added some debug code to the VM to examine the interrupt queue
and discovered that at a certain time the interrupt queue did
contain about 800 interrupts signaling a code cache cleared condition.

Later I discovered how this happened. Somebody wrote code, that
did a lot of become's while the interrupts were disabled.
Each send of #become: clears the code cache and puts a codeCacheCleared
interrupt into the queue.

You can easily reproduce the situation with a code like this:

| coll1 coll2 int |
coll1 := OrderedCollection new.
coll2 := OrderedCollection new.
1 to: 800 do: [ :i | coll1 add: i printString ].
1 to: 800 do: [ :j | coll2 add: j negated printString. ].
int := Process enableInterrupts: false.
1 to: 800 do: [ :x |
    (coll1 at: x) become: (coll2 at: x) ].
Process enableInterrupts: int.


As soon as interrupts are enabled, each method send will trigger
a pending interrupt to be processed.

But the method sends being performed during the #codeCacheCleared
interrupt will also examine the interrupt queue and so
all the queued interrupts will fill up the stack until a stack
overflow happens.

Regarding the situation of Thomas, I'm betting that some
String>>#at:put: with Asian characters are the reason for
a bunch of becomes.

May be I could shed some light on this matter.

Regards

   Andreas

Andreas Rosenberg | eMail: [hidden email]
APIS GmbH         | Phone: +49 9482 9415-0
Im Haslet 42      | Fax: +49 9482 9415-55
93086 Wörth/D     | WWW: <http://www.apis.de/>
Germany           | <http://www.fmea.de/>




-----Original Message-----
From: Using Visual Smalltalk for Windows/Enterprise
[mailto:[hidden email]]On Behalf Of Thomas Muhr
Sent: Montag, 18. Januar 2010 17:18
To: [hidden email]
Subject: Stack Overflow


Dear all,
does anyone know what is happening here and what could be the cause? The OS
is running as a DBCS (Taiwan).

Regards and happy new year!
- Thomas

ATLAS.ti 6.1.8  SC/DUR: 143 /27764
OS: Windows XP Home Edition Comp: ACER-244074A865 - Tuesday 2009-12-08
18:08:22
Active Window: ¹ï«Ý¥Á²³ vs Psy P'T ªº®t§O

Runtime error: Stack overflow

StackOverflowError(Exception)>>defaultAction
StackOverflowError(Exception)>>activateHandler: <anUndefinedObject>
StackOverflowError(Exception)>>handle
StackOverflowError(Exception)>>signal
StackOverflowError class(Exception class)>>signal
Process>>stackOverflow
Process class>>codeCacheClearedInterrupt
ProcessScheduler(Object)>>vmInterrupt: <#codeCacheClearedInterrupt>
ProcessScheduler>>codeCacheCleared
Process class>>codeCacheClearedInterrupt
ProcessScheduler(Object)>>vmInterrupt: <#codeCacheClearedInterrupt>
ProcessScheduler>>codeCacheCleared
Process class>>codeCacheClearedInterrupt
ProcessScheduler(Object)>>vmInterrupt: <#codeCacheClearedInterrupt>
ProcessScheduler>>codeCacheCleared
Process class>>codeCacheClearedInterrupt
ProcessScheduler(Object)>>vmInterrupt: <#codeCacheClearedInterrupt>
...


„Computers, like every technology, are a vehicle for the transformation of
tradition" (Winograd & Flores, 1987) ATLAS.ti Scientific Software
Development GmbH - Berlin - www.atlasti.com

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Andreas,
thanks for the hint. I just tried the code below and it did not produce an
error. I set the size to 2000 and it still worked.
Sometimes, NOT having a problem in VSE is almost as surprising...

Thomas
800
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