RFR: 8212825: jfr.dcmd log is not shown

[Erik Gahlin]

Hi Yasumasa,

Thanks for filing the bug. Instead of making the call to 
JVM.getJVM().isAvailable() in DcmdStart, could you try to add this to 
the constructor of the LogTag class.

  LogTag(int tagId) {
     id = tagId;
+ // This will initialize the JVM Logger
+    JVMSupport.tryToInitializeJVM();
  }

and add this empty method to the JVMSupport class

+ public void tryToInitializeJVM() {
+ }

This will make sure the logger is always initialized before the LogTag 
class is used. This will fix similar bugs in the other DCmds classes and 
perhaps elsewhere as well.

Run the tests in test\jdk\jdk\jfr to make sure the fix doesn't break 
functionality.

Thanks
Erik

> Hi Erik,
>
> I filed this issue as JDK-8212825, and I uploaded webrev.
> Could you review it?
>
>   http://cr.openjdk.java.net/~ysuenaga/JDK-8212825/webrev.00/
>
>
> Thanks,
>
> Yasumasa
>
>
> On 2018/10/24 0:17, Erik Gahlin wrote:
>> Hi Yasumasa,
>>
>> Please file a bug. Markus and I will not have time to look at this 
>> week (CodeOne), but I will check it out next week. Ping me if I forget.
>>
>> Thanks
>> Erik
>>
>>
>>> On 23 Oct 2018, at 08:10, Yasumasa Suenaga <yasuenag at gmail.com> wrote:
>>>
>>> Hi all,
>>>
>>> I tried to check arguments of -XX:StartFlightRecording via 
>>> -Xlog:jfr+dcmd=debug , but I couldn't.
>>>
>>> jfr.dcmd log will be shown from DCmdStart::execute, but I think it 
>>> has two problems:
>>>
>>>   1. Log level will be not set before showing log.
>>>      LogTag::tagSetLevel is used to decide to show the log. But it 
>>> will be set in
>>>      JNI code which is called by JVM::<clinit>. JVM class is not 
>>> loaded when
>>>      DCmdStart::execute tries to show log.
>>>
>>>   2. `settings` might be null, so NPE will occur when 
>>> DCmdStart::execute tries to
>>>      show log.
>>>
>>> IMHO they can be fixed with following patch. Can I file this problem 
>>> to JBS and send a webrev?
>>> (I'm a Committer of jdk project)
>>>
>>>
>>> ---------------------
>>> diff -r eadd0abbfdf4 
>>> src/jdk.jfr/share/classes/jdk/jfr/internal/dcmd/DCmdStart.java
>>> --- a/src/jdk.jfr/share/classes/jdk/jfr/internal/dcmd/DCmdStart.java 
>>> Tue Oct 23 13:24:36 2018 +0200
>>> +++ b/src/jdk.jfr/share/classes/jdk/jfr/internal/dcmd/DCmdStart.java 
>>> Wed Oct 24 00:10:05 2018 +0900
>>> @@ -34,6 +34,7 @@
>>> import java.util.Arrays;
>>> import java.util.HashMap;
>>> import java.util.Map;
>>> +import java.util.Objects;
>>>
>>> import jdk.jfr.FlightRecorder;
>>> import jdk.jfr.Recording;
>>> @@ -81,9 +82,12 @@
>>>       */
>>>      @SuppressWarnings("resource")
>>>      public String execute(String name, String[] settings, Long 
>>> delay, Long duration, Boolean disk, String path, Long maxAge, Long 
>>> maxSize, Boolean dumpOnExit, Boolean pathToGcRoots) throws 
>>> DCmdException {
>>> +        if (!JVM.getJVM().isAvailable()) {
>>> +            throw new DCmdException("JFR is not available");
>>> +        }
>>>          if (LogTag.JFR_DCMD.shouldLog(LogLevel.DEBUG)) {
>>>              Logger.log(LogTag.JFR_DCMD, LogLevel.DEBUG, "Executing 
>>> DCmdStart: name=" + name +
>>> -                    ", settings=" + Arrays.asList(settings) +
>>> +                    ", settings=" + 
>>> Arrays.asList(Objects.requireNonNullElse(settings, new String[0])) +
>>>                      ", delay=" + delay +
>>>                      ", duration=" + duration +
>>>                      ", disk=" + disk+
>>> ---------------------
>>>
>>>
>>> Thanks,
>>>
>>> Yasumasa
>>