Hi,
Could you please review the fix for JDK-8170299: Debugger does not stop inside
the low memory notifications code.
With the current implementation 'debugger does not stop inside the low memory
*notifications* code'
This is expected as the notification code is getting executed with the service
thread, which is a hidden thread.
shafi@shafi-ahmad:~/Java/jdk8/jdk8u-dev$ jdb -Xmx32m MemoryWarningSystem
Initializing jdb ...
> stop at MemoryWarningSystem$1:25
Deferring breakpoint MemoryWarningSystem$1:25.
It will be set after the class is loaded.
> run
run MemoryWarningSystem
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
. . .
> quit
Breakpoint not hit.
With the attached webrev, jdb stop at breakpoint inside notification code.
shshahma@slc12kkg:/scratch/shshahma/Java/jdk-dev$ jdb -Xmx128m
MemoryWarningSystem
Initializing jdb ...
> stop at MemoryWarningSystem$1:25
Deferring breakpoint MemoryWarningSystem$1:25.
It will be set after the class is loaded.
> run
run MemoryWarningSystem
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
>
VM Started: Set deferred breakpoint MemoryWarningSystem$1:25
Breakpoint hit: "thread=Debugger", MemoryWarningSystem$1.memoryUsageLow(),
line=25 bci=0
25 System.out.println("Memory usage low!!!");
Debugger[1] where
[1] MemoryWarningSystem$1.memoryUsageLow (MemoryWarningSystem.java:25)
[2] MemoryWarningSystem$2.handleNotification (MemoryWarningSystem.java:48)
[3] javax.management.NotificationBroadcasterSupport.handleNotification
(NotificationBroadcasterSupport.java:284)
[4] javax.management.NotificationBroadcasterSupport$SendNotifJob.run
(NotificationBroadcasterSupport.java:361)
[5] java.util.concurrent.ThreadPoolExecutor.runWorker
(ThreadPoolExecutor.java:1,135)
[6] java.util.concurrent.ThreadPoolExecutor$Worker.run
(ThreadPoolExecutor.java:635)
[7] java.lang.Thread.run (Thread.java:844)
[8] jdk.internal.misc.InnocuousThread.run (InnocuousThread.java:134)
Debugger[1] list
21
22 MemoryWarningSystem mws = new MemoryWarningSystem();
23 mws.addListener(new MemoryWarningSystem.Listener() {
24 public void memoryUsageLow(long usedMemory, long maxMemory) {
25 => System.out.println("Memory usage low!!!");
26 double percentageUsed = ((double) usedMemory) / maxMemory;
27 System.out.println("percentageUsed = " + percentageUsed);
28 MemoryWarningSystem.setPercentageUsageThreshold(0.8);
29 }
30 });
Debugger[1] threads
Group system:
(java.lang.ref.Reference$ReferenceHandler)0x362 Reference Handler running
(java.lang.ref.Finalizer$FinalizerThread)0x361 Finalizer cond.
waiting
(java.lang.Thread)0x360 Signal Dispatcher running
Group main:
(java.lang.Thread)0x1 main running
Group InnocuousThreadGroup:
(jdk.internal.misc.InnocuousThread)0x35f Common-Cleaner cond.
waiting
(jdk.internal.misc.InnocuousThread)0x4f1 Debugger running (at
breakpoint)
Debugger[1] step
> Memory usage low!!!
Step completed: "thread=Debugger", MemoryWarningSystem$1.memoryUsageLow(),
line=26 bci=8
26 double percentageUsed = ((double) usedMemory) / maxMemory;
Please see the newly created thread " (jdk.internal.misc.InnocuousThread)0x4f1
Debugger running (at breakpoint)".
In the change, the class 'MemoryImpl' is derived from class
'NotificationBroadcasterSupport' instead of class 'NotificationEmitterSupport'
NotificationBroadcastSupport takes an Executor, in the constructor of
MemoryImpl we are calling super() with an executor, which is a visible thread.
The method hasListeners() is referenced inside MemoryImpl.java and defined in
NotificationEmitterSupport.
This method is not present in NotificationBroadcasterSupport so I added it to
NotificationBroadcasterSupport.
Jdk10 bug: https://bugs.openjdk.java.net/browse/JDK-8170299
Webrev link: http://cr.openjdk.java.net/~shshahma/8170299/webrev.02/
Testing: jprt -testset core, rbt --test nsk.jvmti.testlist,nsk.jdi.testlist.
Regards,
Shafi
