RFR: 8221730: jcmd process name matching broken

[Daniil Titov]

Please review the change that makes jcmd process name matching on Linux platform consistent with pre-existing behavior. 

On other platforms (and on Linux platform before changes [3]) the jcmd uses system property "sun.rt.javaCommand"  (see sun.jvmstat.monitor. MonitoredVmUtil.mainClass(MonitoredVm, boolean) that is called from sun.tools.common. ProcessArgumentMatcher at line 96) and treats the part before the first space as a main class when matching the process name. However, if the application  is started with -jar option this part contains the path to the jar file. If  -m or --module option is used this part contains the module name and the main class (if the main class was specified in the command line) in the format <modulename>/<mainclass>.  After changes [3] , on Linux platform the proc filesystem is used to find a Java process, however, it always matches the process name against the main class regardless what options were used to launch the application. This created discrepancies between old and new behavior on Linux platform as well as between behavior on Linux and other platforms. Th!
 e fix changes sun.tool.ProcessHelper (that was introduced in [3]) to correct these discrepancies.


Reference:
[1]  Webrev: http://cr.openjdk.java.net/~dtitov/8221730/webrev.01
[2] Bug: https://bugs.openjdk.java.net/browse/JDK-8221730
[3] https://bugs.openjdk.java.net/browse/JDK-8205654 


Thanks!
--Daniil