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Re: [aspectj-dev] Loadtime Weaving Deadlock

Ron,

I am puzzled that you think this problem has gone away in JDK 1.5. A quick look at the code shows a synchronized block in ObjectInputStream.verifySubclass() using a static variable so the same global lock would seem to still exist. I am also puzzled by your suggested solution. I am not sure how you could persuade serialization to preload classes because you don't know what they are until you read the object stream.

A quick search of the weaver module shows that ResolvedTypeMunger is the only a single use of ObjectStreamClass. Perhaps if this information is only needed for weaveinfo messages then when that option is not used we could avoid reading it. There is already a check to avoid reading the attribute for aspects built with versions of AspectJ older than 1.5.

Matthew Webster
AOSD Project
Java Technology Centre, MP146
IBM United Kingdom Limited
Hursley Park, Winchester,  SO21 2JN, England
Telephone: +44 196 2816139 (external) 246139 (internal)


"Ron Bodkin" <rbodkin@xxxxxxxxxxxxxx>
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27/02/2007 16:43

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[aspectj-dev] Loadtime Weaving Deadlock





Two of our users have reported a deadlock in load-time weaving on a 1.4 VM, e.g., see http://www.glassbox.com/forum/forum/viewthread?thread=146
 
This happens in a 1.4 VM because ObjectInputStream locks sun.misc.SoftCache (used to hold verified subclasses), whereas in 1.5 they use a ConcurrentHashMap so you don’t get the deadlocking behavior. I’m thinking that the best fix for this is to somehow force ObjectInputStream to load a class before weaving so that it won’t trigger class loading during weaving. This would be a fix/work-around in the 1.4 VM adapter we’re using, so it’s not an AspectJ issue per se, but I’d value input on how to best resolve this.
 
Thanks,
Ron
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