RFR JDK-8170089: nsk/jdi/EventSet/resume/resume008: ERROR: suspendCounts don't match for : Common-Cleaner

[Gary Adams]

A race condition exists between the debugger and the debuggee.

The first test thread is started with SUSPEND_NONE policy set.
While processing the thread start event the debugger captures
an initial set of thread suspend counts and resumes the
debuggee vm. If the debuggee advances quickly it reaches
the breakpoint set for methodForCommunication. Since the breakpoint
carries with it SUSPEND_ALL policy, when the debugger captures a second
set of suspend counts, it will not match the expected counts for
a SUSPEND_NONE scenario.

The proposed fix introduces a yield in the debuggee test thread run method
to allow the debugger to get the expected sampled values.

   Issue: https://bugs.openjdk.java.net/browse/JDK-8170089
   Webrev: http://cr.openjdk.java.net/~gadams/8170089/webrev.00/


test/hotspot/jtreg/vmTestbase/nsk/share/jdi/TestDebuggerType1.java:
...
    186        private void setCommunicationBreakpoint(ReferenceType 
refType, String methodName) {
    187            Method method = debuggee.methodByName(refType, 
methodName);
    188            Location location = null;
    189            try {
    190                location = method.allLineLocations().get(0);
    191            } catch (AbsentInformationException e) {
    192                throw new Failure(e);
    193            }
    194            bpRequest = debuggee.makeBreakpoint(location);
    195

    196            bpRequest.setSuspendPolicy(EventRequest.SUSPEND_ALL);

    197            bpRequest.putProperty("number", "zero");
    198            bpRequest.enable();
    199
    200            eventHandler.addListener(
    201                 new EventHandler.EventListener() {
    202                     public boolean eventReceived(Event event) {
    203                        if (event instanceof BreakpointEvent && 
bpRequest.equals(event.request())) {
    204                            synchronized(eventHandler) {
    205                                display("Received communication 
breakpoint event.");
    206                                bpCount++;
    207                                eventHandler.notifyAll();
    208                            }
    209                            return true;
    210                        }
    211                        return false;
    212                     }
    213                 }
    214            );
    215        }


test/hotspot/jtreg/vmTestbase/nsk/jdi/EventSet/resume/resume008.java:
...
    140                    display("......--> vm.suspend();");
    141                    vm.suspend();
    142
    143                    display("        getting : Map<String, 
Integer> suspendsCounts1");
    144
    145                    Map<String, Integer> suspendsCounts1 = new 
HashMap<String, Integer>();
    146                    for (ThreadReference threadReference : 
vm.allThreads()) {
    147                        
suspendsCounts1.put(threadReference.name(), threadReference.suspendCount());
    148                    }
    149                    display(suspendsCounts1.toString());
    150
    151                    display("        eventSet.resume;");
    152                    eventSet.resume();
    153
    154                    display("        getting : Map<String, 
Integer> suspendsCounts2");

This is where the breakpoint is encountered before the second set of 
suspend counts is acquired.

    155                    Map<String, Integer> suspendsCounts2 = new 
HashMap<String, Integer>();
    156                    for (ThreadReference threadReference : 
vm.allThreads()) {
    157                        
suspendsCounts2.put(threadReference.name(), threadReference.suspendCount());
    158                    }
    159                    display(suspendsCounts2.toString());