sun.java.launcher.pid property usage

[Baesken, Matthias]

Hi David, thanks for the additional  information .
I opened  

https://bugs.openjdk.java.net/browse/JDK-8231171

8231171: remove reamining sun.java.launcher.pid references

  to do the additional cleanup .

Best regards, Matthias


> -----Original Message-----
> From: David Holmes <david.holmes at oracle.com>
> Sent: Mittwoch, 18. September 2019 03:16
> To: Baesken, Matthias <matthias.baesken at sap.com>; 'hotspot-
> dev at openjdk.java.net' <hotspot-dev at openjdk.java.net>
> Subject: Re: sun.java.launcher.pid property usage
> 
> Hi Matthias,
> 
> On 18/09/2019 12:18 am, Baesken, Matthias wrote:
> > Hello,  while looking at some  atoi usages in the codebase I started to
> wonder about the  "sun.java.launcher.pid"  property.
> > Currently in java_md_solinux.c  the property is set on Linux only  by default
> (code is guarded #ifdef __linux__ ).
> > Later it is passed  to the int  variable _sun_java_launcher_pid
> (arguments.cpp) and can be retrieved by sun_java_launcher_pid() .
> > However only in src/hotspot/os/bsd/os_bsd.cpp it is really used.
> >
> > Is the property still supported (one would need to set it from user side on
> the command line on non-Linux because it is not set by default on
> bsd/macOS) ?
> > Can the coding be removed (or should it enabled for BSD/Mac like we do
> on Linux) ?
> >
> > The os_bsd comment mentiones the bug 6351349 :
> >
> > https://bugs.java.com/bugdatabase/view_bug.do?bug_id=6351349
> > JDK-6351349 : On linux with the old thread lib, jps should return the same
> PID as $!
> >
> > but this looks very old.
> 
> That was the bug that added this code as it was needed on Linux with
> LinuxThreads. The code was then removed on Linux under
> 
> https://bugs.openjdk.java.net/browse/JDK-8078513
> 
> The review thread starts here:
> 
> http://mail.openjdk.java.net/pipermail/hotspot-runtime-dev/2015-
> May/014709.html
> 
> I think we were focussed solely on cleaning up the hotspot Linux code
> and didn't really look at the wider implication of the use of
> sun.java.launcher.pid. The code in os_bsd.cpp was simply copied from the
> Linux code without giving it any consideration - as you can tell from
> the comment:
> 
>    // With BsdThreads the JavaMain thread pid (primordial thread)
>    // is different than the pid of the java launcher thread.
>    // So, on Bsd, the launcher thread pid is passed to the VM
>    // via the sun.java.launcher.pid property.
> 
> where you can tell that Linux was simply replaced by Bsd, so we
> reference the non-existent BsdThreads :(
> 
> So yes this all seems to be dead code that should be removed - core-libs
> folk will need to be involved of course as they own the launcher. :) It
> looks like SetJavaLauncherPlatformProps() can be removed completely.
> 
> Thanks,
> David
> 
> > Best regards, Matthias
> >
> >
> >
> >
> > coding parts mentioned :
> >
> > src/hotspot/os/bsd/os_bsd.cpp
> > -----------------------------------
> >
> > void os::init(void) {
> >    char dummy;   // used to get a guess on initial stack address
> >
> >    // With BsdThreads the JavaMain thread pid (primordial thread)
> >    // is different than the pid of the java launcher thread.
> >    // So, on Bsd, the launcher thread pid is passed to the VM
> >    // via the sun.java.launcher.pid property.
> >    // Use this property instead of getpid() if it was correctly passed.
> >    // See bug 6351349.
> >    pid_t java_launcher_pid = (pid_t) Arguments::sun_java_launcher_pid();
> >
> >    _initial_pid = (java_launcher_pid > 0) ? java_launcher_pid : getpid();
> >
> >
> > arguments.cpp / hpp
> > ---------------------
> >
> >      if (match_option(option, "-Dsun.java.launcher.pid=", &tail)) {
> >        _sun_java_launcher_pid = atoi(tail);
> >        continue;
> >      }
> >
> >    static int sun_java_launcher_pid()        { return _sun_java_launcher_pid; }
> >
> >
> > java_md_solinux.c
> > ---------------------
> >
> > void SetJavaLauncherPlatformProps() {
> >     /* Linux only */
> > #ifdef __linux__
> >      const char *substr = "-Dsun.java.launcher.pid=";
> >      char *pid_prop_str = (char *)JLI_MemAlloc(JLI_StrLen(substr) +
> MAX_PID_STR_SZ + 1);
> >      sprintf(pid_prop_str, "%s%d", substr, getpid());
> >      AddOption(pid_prop_str, NULL);
> > #endif /* __linux__ */
> > }
> >