review for 7150390: JFR test crashed on assert(_jni_lock_count == count) failed: must be equal

[Vladimir Kozlov]

Looks good.

Vladimir

Tom Rodriguez wrote:
> http://cr.openjdk.java.net/~never/7150390
> 33 lines changed: 28 ins; 4 del; 1 mod; 7748 unchg
> 
> 7150390: JFR test crashed on assert(_jni_lock_count == count) failed: must be equal
> Reviewed-by:
> 
> Threads which have been suspended weren't being visited by the logic
> for maintaining the shared JNI critical count, resuling in incorrect
> values.  It's a very rare problem that could only occur as a result of
> JVMTI suspending a thread in the middle of a JNI critical operation
> which should in general be rare.  It showed up in the nightlies with
> regularity but I was unable to reproduce the original problem.  Adding
> the new visited flag identified the issue immediately.  Tested with
> tests from nightlies and the nsk JVMTI related tests.
>