RFR: JDK-8152690: main thread does not have native thread name

[Robbin Ehn]

Hi,

On 03/30/2016 11:41 AM, Yasumasa Suenaga wrote:
> Hi Robbin,
>
> 2016/03/30 18:22 "Robbin Ehn" <robbin.ehn at oracle.com
> <mailto:robbin.ehn at oracle.com>>:
>  >
>  > Hi Yasumasa,
>  >
>  >
>  > On 03/25/2016 12:48 AM, Yasumasa Suenaga wrote:
>  >>
>  >> Hi Robbin,
>  >> 2016/03/25 1:51 "Robbin Ehn" <robbin.ehn at oracle.com
> <mailto:robbin.ehn at oracle.com>
>  >> <mailto:robbin.ehn at oracle.com <mailto:robbin.ehn at oracle.com>>>:
>  >>
>  >>  >
>  >>  > Hi Yasumasa,
>  >>  >
>  >>  > I'm not sure why you don't set it:
>  >>  >
>  >>  > diff -r ded6ef79c770 src/share/vm/runtime/thread.cpp
>  >>  > --- a/src/share/vm/runtime/thread.cpp   Thu Mar 24 13:09:16 2016
> +0000
>  >>  > +++ b/src/share/vm/runtime/thread.cpp   Thu Mar 24 17:40:09 2016
> +0100
>  >>  > @@ -3584,6 +3584,7 @@
>  >>  >    JavaThread* main_thread = new JavaThread();
>  >>  >    main_thread->set_thread_state(_thread_in_vm);
>  >>  >    main_thread->initialize_thread_current();
>  >>  > +  main_thread->set_native_thread_name("main");
>  >>  >    // must do this before set_active_handles
>  >>  >    main_thread->record_stack_base_and_size();
>  >>  >    main_thread->set_active_handles(JNIHandleBlock::allocate_block());
>  >>  >
>  >>  > here instead? Am I missing something?
>  >>
>  >> Native thread name is the same to thread name in Thread class.
>  >> It is set in c'tor in Thread or setName().
>  >> If you create new thread in Java app, native thread name will be set at
>  >> startup. However, main thread is already starte in VM.
>  >> Thread name for "main" is set in create_initial_thread().
>  >> I think that the place of setting thrrad name should be the same.
>  >
>  >
>  > Yes, I see your point. But then something like this is nicer, no?
>  >
>  > --- a/src/share/vm/runtime/thread.cpp   Tue Mar 29 09:43:05 2016 +0200
>  > +++ b/src/share/vm/runtime/thread.cpp   Wed Mar 30 10:51:12 2016 +0200
>  > @@ -981,6 +981,7 @@
>  >  // Creates the initial Thread
>  >  static oop create_initial_thread(Handle thread_group, JavaThread*
> thread,
>  >                                   TRAPS) {
>  > +  static const char* initial_thread_name = "main";
>  >    Klass* k =
> SystemDictionary::resolve_or_fail(vmSymbols::java_lang_Thread(), true,
> CHECK_NULL);
>  >    instanceKlassHandle klass (THREAD, k);
>  >    instanceHandle thread_oop =
> klass->allocate_instance_handle(CHECK_NULL);
>  > @@ -988,8 +989,10 @@
>  >    java_lang_Thread::set_thread(thread_oop(), thread);
>  >    java_lang_Thread::set_priority(thread_oop(), NormPriority);
>  >    thread->set_threadObj(thread_oop());
>  > -
>  > -  Handle string = java_lang_String::create_from_str("main", CHECK_NULL);
>  > +
>  > +  thread->set_native_thread_name(initial_thread_name);
>  > +
>  > +  Handle string =
> java_lang_String::create_from_str(initial_thread_name, CHECK_NULL);
>  >
>  >    JavaValue result(T_VOID);
>  >    JavaCalls::call_special(&result, thread_oop,
>
> Okay, I will upload new webrev later.

Thanks!

>
>  >>  > The launcher seem to name itself 'java' and naming this thread just
>  >>  > 'main' is confusing to me.
>  >>  >
>  >>  > E.g. so main thread of the process (and thus the process) is
> 'java' but
>  >>  > first JavaThread is 'main'.
>  >>
>  >> The native main thread in the process is not JavaThread. It is waiting
>  >> for ending of Java main thread with pthread_join().
>  >> set_native_thread_name() is for JavaThread. So I think that we do not
>  >> need to call it for native main thread.
>  >
>  >
>  > Not sure if we can change it anyhow, since we want java and native
> name to be the same and java thread name might have some dependents.
>  >
>  > The name is visible in e.g. /proc.
>  >
>  > $ ps H -C java -o 'pid tid comm' | head -4
>  >   PID   TID COMMAND
>  >  6423  6423 java
>  >  6423  6424 main
>  >  6423  6425 GC Thread#0
>  >
>  > It would be nice with something like 'Java Main Thread'.
>
> I do not think so.
> Native main thread might not be a Java launcher - e.g. Apache
> commons-daemon, JNI application, etc.
>
> If you want to change native main thread name, I think that we have to
> change Java launcher code.
> Should I include it in new webrev?

No

Thanks again!

/Robbin

>
> Thanks,
>
> Yasumasa
>
>  > Thanks
>  >
>  > /Robbin
>  >
>  >
>  >>
>  >> Thanks,
>  >>
>  >> Yasumasa
>  >>
>  >>  > Thanks!
>  >>  >
>  >>  > /Robbin
>  >>  >
>  >>  > On 03/24/2016 03:26 PM, Yasumasa Suenaga wrote:
>  >>  > > Hi all,
>  >>  > >
>  >>  > > HotSpot for Linux will set thread name via pthread_setname_np().
>  >>  > > However, main thread does not have it.
>  >>  > >
>  >>  > > All JavaThread have native name, and main thread is JavaThread.
>  >>  > > For consistency, main thread should have native thread name.
>  >>  > >
>  >>  > > I uploaded a webrev. Could you review it?
>  >>  > >
>  >>  > > http://cr.openjdk.java.net/~ysuenaga/JDK-8152690/webrev.00/
>  >>  > >
>  >>  > > I cannot access JPRT.
>  >>  > > So I need a sponsor.
>  >>  > >
>  >>  > >
>  >>  > > Thanks,
>  >>  > >
>  >>  > > Yasumasa
>  >>  > >
>  >>
>