please review: Draft proposal for Class loader deadlock fix

Karen Kinnear Karen.Kinnear at Sun.COM
Thu Nov 13 18:24:45 UTC 2008

Dear Java Developers,

For several years we have been hearing requests from you for a fix for  
the class loader problem, 4670071, in which custom class loaders can  
deadlock. We recognize this is an important issue for many of our  
customers and apologize for how long it has taken us to find a  
solution. We have been working on the underlying technology changes  
for this for several years, improving the VM class loading for JDK5,  
JDK6 and Hotspot 10. We now have the VM technology in place and are  
ready to propose minimal API changes which would allow custom class  
loaders to load multiple classes in parallel without deadlocking. We  
discussed an earlier proposal at JavaOne 2008 and believe we have  
improved and simplified our approach based on the very helpful  
feedback we received there and in subsequent communications.

Over the years, many of you have provided valuable feedback and have  
participated in discussions on finding a solution for this problem.  
Thank you. We are now pleased to announce the availability of the  
initial draft of the proposal for fixing the class loader deadlock  
problem, 4670071. We would like to invite you to review the proposal  
and provide us your feedback so we can make sure that the eventual  
solution will meet your need.

The proposal is attached to this email. We will post updates to the  
proposal at

Our current goal is to make a prototype available in mid December 2008  
after incorporating feedback.

We have a plea for you, we could use additional test cases. We have a  
small number of samples that we are very grateful for and have used to  
test the multiple prototypes tried so far. Additional test cases could  
make a big difference in our understanding of any design goals or  
constraints that we have missed as well as in our confidence that a  
given solution will work. If you have any test cases, sample code  
which show the problems you care about, please send them to us.

We want to thank you for taking the time to help us resolve this  
challenging problem, and thank you for your patience. Please send your  
feedback and comments to this mailing list or to any of the following  
development engineers.

Karen Kinnear, VM runtime technical lead -  karen.kinnear at
Valerie Peng, VM core libraries - yu-ching.peng at
Jeff Nisewanger, VM core libraries - jeff.nisewanger at

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <>

More information about the core-libs-dev mailing list