Hi Gary,
I've been having trouble following the control flow of this test. One
thing I've stumbled across is the following:
/* A debuggee class must define 'methodForCommunication'
* method and invoke it in points of synchronization
* with a debugger.
*/
setCommunicationBreakpoint(debuggeeClass,"methodForCommunication");
So why isn't this mode of synchronization good enough? Is it because it
was not designed with the understanding that the debugger might be doing
suspended thread counts, and suspending all threads at the breakpoint
messes up the test?
From what I can tell of the test, after the debuggee is started and
hits the default breakpoint at the start of main(), the debugger then
does a vm.resume() at the start of the for loop in the runTest() method.
The debuggee then creates a thread and calls methodForCommunication().
There is already a breakpoint set there by the above debuggee code. It's
unclear to me what happens as a result of this breakpoint and how it
serves the test. Also unclear to me who is responsible for the
vm.resume() after the breakpoint is hit.
The debugger then requests all ThreadStart events, requesting that no
threads be disabled when it is sent. I think you are saying that when
the ThreadStart event comes in, sometimes we are at the
methodForCommunication breakpoint, with all threads disabled, and this
messes up the thread suspend counts. You want to delay 100ms so the
breakpoint event can be processed and threads resumed again (although I
can't see who actually resumes the thread after hitting the
methodForCommunication breakpoint).
Chris
On 7/17/18 8:33 AM, Gary Adams wrote:
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());
