review (S) for 6958668: repeated uncommon trapping for new of klass which is being initialized

[Vladimir Kozlov]

Looks good.

Vladimir

On 7/1/10 6:52 PM, Tom Rodriguez wrote:
> http://cr.openjdk.java.net/~never/6958668
>
> 6958668: repeated uncommon trapping for new of klass which is being initialized
> Reviewed-by:
>
> During the execution of a class initializer only the initializing
> thread is allowed to create instances of the class.  Currently in C2
> this is handled by emitting an uncommon trap.  If an application
> creates a lot of instances using this idiom it can lead to long
> sequences of compile, uncommon trap, recompile, uncommon trap.
> Instead C2 should emit a guarded new that allows the proper thread to
> perform allocations throws out the code once initialization is
> complete.  Ideally we should just be able to test that the init_thread
> is the current thread but the init_thread is never set back to null so
> the init_state is additionally being checked.  I'm planning to
> separately fix the clearing the init_thread since C1 mistakenly
> expects it to be cleared.  This fix is going to be backported to an
> update at some point.  Tested with users application and test case
> which I haven't bothered including though it is in the bug report.