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Bug 333242

Summary:	Double checked locking in WorkbenchErrorHandler
Product:	[Eclipse Project] Platform	Reporter:	Ralf Sternberg <rsternberg>
Component:	UI	Assignee:	Platform-UI-Inbox <Platform-UI-Inbox>
Status:	CLOSED INVALID	QA Contact:
Severity:	normal
Priority:	P3	CC:	krzysztof.daniel, remy.suen
Version:	3.7
Target Milestone:	---
Hardware:	PC
OS:	Linux
Whiteboard:

Description Ralf Sternberg

2010-12-27 09:20:29 EST

The fix for bug 218137 introduced double checked locking in WorkbenchErrorHandler#getStatusDialogManager().
This pattern is considered broken because this can return partially constructed objects to clients.
See http://en.wikipedia.org/wiki/Double-checked_locking,
 http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html

Comment 1 Krzysztof Daniel

2011-01-03 08:23:41 EST

The pattern is considered broken only for multithreaded apps.
WorkbenchErrorHandler#handle ensures that all private methods are called only from UI thread, therefore partial initialization of statusDialogManager field will not happen.

Feel free to reopen if I am wrong.

Comment 2 Ralf Sternberg

2011-01-03 18:59:42 EST

(In reply to comment #1)
> The pattern is considered broken only for multithreaded apps.
> WorkbenchErrorHandler#handle ensures that all private methods are called only
> from UI thread, therefore partial initialization of statusDialogManager field
> will not happen.
> 
> Feel free to reopen if I am wrong.

Oh, I was not aware that this method is only called from the UIThread.

But then, just out of curiosity: what's the use of this synchronized block at all given that the private field statusDialogManager is only accessed from this very method and therefore only from the UIThread?