There is nothing wrong with the breakpoint in methodForCommunication.
The test uses it to make sure the threads are each tested separately.
The breakpoint eventhandler just displays a message, increments a
counter
and returns.
Let me step through resume008a the debugee to help clarify ...
1. The test thread is created and the synchronized break point is
observed. lines 101-102
2. The thread is started. lines 104,135-137
2a. The main thread blocks on a local object. lines 133, 139
2b. The test thread is started. lines 137,
A run entered message is displayed, line 159
The main thread lock object is notified, line 167
2b1. The main thread continues. line 167, 146
The next test thread is created. line 106
The synchronized breakpoint is observed, line 107
2b2. A run exited message is displayed, line 169
On the resume008 debugger side ...
1. On a thread start event the debugee is suspended, line 141
2. Messages are displayed and a first set of thread suspend counts
is acquired. lines 143-151
3. The threads are resumed, line 152
--->
4. Messages are displayed and a second set of thread suspend
counts is acquired. lines 154-159
The way the test is written the expectation is the debugger steps
2,3,4 will all happen
while the test thread is running.
When the debugger resumes the debuggee threads (debugger step 3)
the debuggee continues from where it left off (debuggee steps
2b,2b1,2b2)
If we complete debuggee step 2b1 (line 107) before the debugger
completes step 4 line 159,
then the synchronized breakpoint will suspend the vm and the counts
will not match
for the SUSPEND_NONE test thread start.
resume008a.java:
100 case 0:
101 thread0 = new
Threadresume008a("thread0");
102 methodForCommunication();
103
104 threadStart(thread0);
105
106 thread1 = new
Threadresume008a("thread1");
107 methodForCommunication();
108 break;
...
135 static int threadStart(Thread t) {
136 synchronized (waitnotifyObj) {
137 t.start();
138 try {
139 waitnotifyObj.wait();
140 } catch ( Exception e) {
141 exitCode = FAILED;
142 logErr(" Exception : " + e );
143 return FAILED;
144 }
145 }
146 return PASSED;
147 }
149 static class Threadresume008a extends Thread {
...
157
158 public void run() {
159 log1(" 'run': enter :: threadName == " +
tName);
This is the proposed fix that will let the debugger complete it's
second
acquisition of suspend counts while the test thread is still running.
160 // Yield, so the start thread event processing
can be completed.
161 try {
162 Thread.sleep(100);
163 } catch (InterruptedException e) {
164 // ignored
165 }
166 synchronized (waitnotifyObj) {
167 waitnotifyObj.notify();
168 }
169 log1(" 'run': exit :: threadName == " +
tName);
170 return;
171 }
172 }
150
151 String tName = null;
152
153 public Threadresume008a(String threadName) {
154 super(threadName);
155 tName = threadName;
156 }
157
158 public void run() {
159 log1(" 'run': enter :: threadName == " +
tName);
160 // Yield, so the start thread event processing
can be completed.
161 try {
162 Thread.sleep(100);
163 } catch (InterruptedException e) {
164 // ignored
165 }
166 synchronized (waitnotifyObj) {
167 waitnotifyObj.notify();
168 }
169 log1(" 'run': exit :: threadName == " +
tName);
170 return;
171 }
172 }
On 7/18/18, 2:38 AM, Chris Plummer wrote:
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());
