Staffan Larsen wrote:
I think what you need to do is wait for the VMStartEvent before you add
requests to the VM. Note this paragraph from the VirtualMachine doc:
Note that a target VM launched by a launching connector is not
guaranteed to be stable until after the VMStartEvent has been
received.
I may miss something here, I believe VMStartEvent must be the first
event, when the test got ClassPrepareEvent, it must already received
VMStartEvent.
I think adding code that looks something like this will make the test stable:
VirtualMachine vm = launchTarget(CLASS_NAME);
EventQueue eventQueue = vm.eventQueue();
boolean started = false;
while(!started) {
EventSet eventSet = eventQueue.remove();
for (Event event : eventSet) {
if (event instanceof VMStartEvent) {
started = true;
}
if (event instanceof VMDeathEvent
|| event instanceof VMDisconnectEvent) {
throw new Error("VM died before it started...:"+event);
}
}
}
System.out.println("Vm launched");
The code you proposed could improve the test, it made sure that
TestPostFieldModification was started, but I am afraid that it did not
address the issue causing the failure, the issue I believe was that
TestPostFieldModification exited before or during FieldMonitor called
addFieldWatch(), that was why addFieldWatch() received
VMDisconnectedException. When the test was treating ClassPrepareEvent,
even if VMDeathEvent or VMDisconnectEvent arrived, it must be still
waiting in the eventQueue because it arrived after ClassPrepareEvent.
My fix was to not allow TestPostFieldModification to exit before
addFieldWatch() was done.
There is also no reason to call addFieldWatch() before the ClassPrepareEvent has been received. The call to vm..classesByName() will just return an empty list anyway.
I do not know why the test called addFieldWatch before ClassPrepareEvent
had been received, but yes the returned list was empty, so agree to
remove it.
While you are in there you can also remove the unused StringBuffer near the top
of main().
Yes it was already removed in version 01
Here is the new webrev:
http://cr.openjdk.java.net/~sjiang/JDK-8007710/02/
Thanks,
Shanliang
Thanks,
/Staffan
On 11 feb 2014, at 18:30, shanliang <shanliang.ji...@oracle.com> wrote:
Here is the new fix in which FieldMonitor will write to
TestPostFieldModification, to inform the latter to quit, as suggested bu
Jaroslav
http://cr.openjdk.java.net/~sjiang/JDK-8007710/01/
Thanks,
Shanliang
shanliang wrote:
shanliang wrote:
Jaroslav Bachorik wrote:
On 11.2.2014 16:31, shanliang wrote:
Staffan Larsen wrote:
Hi Shanliang,
I can’t quite see how the test can fail in this way. When the
ClassPrepareEvent happens, the debuggee will be suspended. So when
addFieldWatch() is called, the debuggee should not have moved.
I am not expert of jdi so I may miss something here. I checked the
failure trace and saw the report exception happen when FieldMonitor
received ClassPrepareEvent and was doing addFieldWatch. FieldMonitor did
call "vm.resume()" before treating events.
AFAICS, calling vm.resume() results in an almost immediate debuggee death. The gc()
invoking thread "d" is flagged as a deamon and as such doesn't prevent the
process from exiting. The other thread is not a daemon but will finish in only few cycles.
I looked at the class com.sun.jdi.VirtualMachine, here is the Javadoc of the method
"resume":
/**
* Continues the execution of the application running in this
* virtual machine. All threads are resumed as documented in
* {@link ThreadReference#resume}.
*
* @throws VMCannotBeModifiedException if the VirtualMachine is read-only -
see {@link VirtualMachine#canBeModified()}.
*
* @see #suspend
*/
void resume();
My understanding is that the debuggee resumes to work after this call, instead
to die?
In fact the problem is here, the vm (TestPostFieldModification) should not die
before FieldMonitor finishes addFieldWatch.
Shanliang
I reproduced the bug by add sleep(1000) after vm.resume() but before
calling eventQueue.remove();
It looks like some kind of synchronization between the debugger and the
debuggee is necessary. But I wonder if you should better use the
process.getOuptuptStream() to write and flush a message for the debugee
indicating that it can exit. And in the debugee you would just do
System.in.read() as the last statement in the main() method. Seems more robust
than involving files.
It could work, but creating a file in the testing directory should have no
issue, but yes maybe less performance.
Thanks,
Shanliang
Cheers,
-JB-
Thanks,
Shanliang
One problem I do see with the test is that it does not wait for a
VMStartEvent before setting up requests. I’m not sure if that could
cause the failure in the bug report, though.
/Staffan
On 11 feb 2014, at 15:13, shanliang <shanliang.ji...@oracle.com> wrote:
Hi ,
The problem could be that FieldMonitor did not have enough time to
"addFieldWatch" but the vm to monitor (TestPostFieldModification) was
already ended.
So we should make sure that TestPostFieldModification exits after
FieldMonitor has done necessary. The solution proposed here is that
FieldMonitor creates a file after adding field watching, and
TestPostFieldModification quits only after finding the file.
web:
http://icncweb.fr.oracle.com/~shjiang/webrev/8007710/00/
bug:
https://bugs.openjdk.java.net/browse/JDK-8007710
Thanks,
Shanliang
