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

[Robbin Ehn]

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>>:
>  >
>  > 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,


>
>  > 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'.

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
>  > >
>