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

[Yasumasa Suenaga]

Hi Robbin,

2016/03/30 18:22 "Robbin Ehn" <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>>:
>>
>>  >
>>  > 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.

>>  > 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?

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
>>  > >
>>