RFR(S): 8134103: JVMTI_ERROR_WRONG_PHASE(112): on checking for an interface

[serguei.spitsyn at oracle.com]

Please, review the JDK 10 fix for:
   https://bugs.openjdk.java.net/browse/JDK-8134103


Webrev:
http://cr.openjdk.java.net/~sspitsyn/webrevs/2017/hotspot/8134103-jdi-wrong-phase.1/


Summary:
   This is an intermittent issue in the debugger back-end (JDWP agent)
   that impacts the nightly testing stability.
   The fix adds check guards of gdata->vmDead condition to the:
    - debugLoop (JDWP Event Helper thread) and
    - commandLoop (JDWP Transport Listener thread)
   The commands are ignored in the DEAD phase.

   The check guard in the debugLoop already existed but only for 
VirtualMachine
   command set, so it has been extended to commands from all JDWP 
command sets.

   I suspect, this bug could also cause some of the timeout and socket 
related issues.


Testing:
   The fix was tested with the nsk.jdi, jtreg com/sun/jdi and 100 runs
   of the hotspot/test/closed/compiler/c1/6507107/HeapwalkingTest.java.
   The test results are very clean.


Thanks,
Serguei