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https://issues.apache.org/jira/browse/TAPESTRY-2561?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12628886#action_12628886
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Howard M. Lewis Ship commented on TAPESTRY-2561:
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Man this is tricky.
Java loads classes as needed. Accessing a method, such as
PublicList.getQueryPublicCallback(), is referencing a previously unloaded
class, which is then loaded. The Java library code is synchronized against the
class loader instance, while other code in T5 is synchronized against the
global mutex.
This is a bit like whack-a-mole.
I think I need to be able to reproduce this on my workstation (duh!).
I would think that synchronizing on the global mutex inside
PackageAwareLoader.findClass() would help ... but that caused a prior deadlock
(I commented out the code at some point).
Looking at the traces, this kind of thing should only happen on the first load
of the page (i.e., a race by multiple threads to initialize the page
instances). Is this true? If you "warm up the app" then start crushing it with
requests, does it fail? In other words, I could use a little more step-by-step
in how you reach the deadlock, and what operating systems are involved.
> Rapidly refreshing a page, even the same page, can cause a deadlock related
> to class loading
> --------------------------------------------------------------------------------------------
>
> Key: TAPESTRY-2561
> URL: https://issues.apache.org/jira/browse/TAPESTRY-2561
> Project: Tapestry
> Issue Type: Bug
> Components: tapestry-core
> Affects Versions: 5.0.14
> Environment: Mac pro, OS Version: Mac OS X 10.5.4 (9E17)
> Java HotSpot(TM) Client VM (1.5.0_13-119 mixed mode,
> sharing)
> Reporter: Steven Woolley
> Assignee: Howard M. Lewis Ship
> Fix For: 5.0.15
>
> Attachments: full thread dump deadlock.txt
>
>
> It was triggered by (accidentally) double clicking a pagelink ;)
> Unfortunately, can't quite repeat it... at least not clicking with a mouse...
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