Please review (S): fix placeholder table entry cleanup

[David Holmes]

Hi Karen,

On 12/10/2012 4:04 AM, Karen Kinnear wrote:
>
> Fix to clean up placeholdertable entries in stackoverflow conditions.
>
> webrev: http://cr.openjdk.java.net/~acorn/7199207/webrev

So the basic problem is that the thread nominally responsible for 
cleaning up the placeholder doesn't because a StackOverflow causes the 
call to resolve_or_fail to issue a return (via the CHECK_ macro) that 
skips the cleanup - right?

So here:

1263       resolve_super_or_fail(class_name, name, class_loader, 
Handle(), false, CHECK_(nh));
1264     }
1265     // Caller's of resolve_super_or_fail need to clean up child's 
placeholder entry
1266     // Because define class path needs to track entry until 
systemDictionary entry created

don't we need to change the CHECK_(nh) to just THREAD as is done in 
handle_parallel_super_load() ?

Also if we're running out of stack do we know that we have enough stack 
to perform this cleanup work? If we don't will we abort instead?

Looking at the miscellaneous comment updates I notice that here:

442 / 867/ 915      // SystemDictionary::do_unloading() asserts that 
classes in the SD are only

we make a claim about an assertion, but in the actual code for 
SystemDictionary::do_unloading there is no direct assertion (I know you 
only added the "in the SD" part :) )

1790 // Assumes classes in the SystemDictionary are only unloaded at a 
safepoint
1791 // Note: anonymous classes are not in the SD

Is it an assumption or requirement? Should 1791 add "and so are not 
unloaded by this method" ? Do anonymous classes deserve some more 
in-depth commentary somewhere in here?

Cheers,
David

> bug link: https://jbs.oracle.com/bugs/browse/JDK-7199207
>
> Thanks to Stefan Karlsson for identifying the problem and
> the initial fix.
>
> Tests run:
> Originally reported chain007 with ThreadStackSize=128 and
> original options.
>
> vm.quick.testlist
> vm.parallel_class_loading.testlist
> jck: non-interactive jck, api, lang
> jtreg: java.lang.instrument
> RunThese full
> ctw nightly.testlist
>
> thanks,
> Karen
>
>