On 10/14/2014 07:22 PM, Mandy Chung wrote:
On 10/13/2014 5:50 AM, David M. Lloyd wrote:
On 10/10/2014 07:31 PM, Mandy Chung wrote:
On 10/10/2014 8:10 AM, Claes Redestad wrote:
Hi all,
please review this patch which attempts to clean up synchronization
and improve scalability when
defining and getting java.lang.Package objects.
I agree with David that getting Package objects are not performance
critical. On the other hand, the code defining/getting Packages is
old and deserves some cleanup especially the synchronization part.
I have a little more information on this subject. We've a possible
(and somewhat likely) deadlock which occurs because one thread can
attempt to define a system class while holding the
java.lang.Package#pkgs lock, while another thread can attempt to get a
package while defining a system class (while holding the class loader
lock). I do not recall whether parallel class loading alleviates this
issue. We solved the problem by loading Packages.getPackages() in
early (single-threaded) bootstrap.
Do you recall what JDK version you observed this possible deadlock? I
wonder if the fix for 7001933 [1] in JDK 7 and 6u25 resolved the
deadlock problem you ran into.
[1] http://hg.openjdk.java.net/jdk9/dev/jdk/rev/4a7da412db38
The change would have been observed in early 2011 so I think it was
probably a JDK 6 version before 25 (which I did not install until April
of that year) - looks like most likely candidate based on my JDK
directory is 1.6.0_22.
So from my perspective, just getting rid of the synchronization on
that field alone makes this change worthwhile.
Yes that's what I think too.
Mandy
--
- DML
