RFR(XS): 8043070: nmethod::verify_interrupt_point() shouldn't enter safepoint

[Igor Veresov]

nmethod::verify_interrupt_point() is called from as part of nmethod verification from ciEnv::register_method() that asserts no safepoint can occur. However verify_interrupt_point() locks a mutex that may potentially safepoint. A sample call stack of when it happens is in the following JBS issue.

JBS: https://bugs.openjdk.java.net/browse/JDK-8043070
Webrev: http://cr.openjdk.java.net/~iveresov/8043070/webrev.00/

igor