JDK-8176828: jtools do not list VM process launched with the debugger option suspend=y

[Chris Plummer]

Sorry, meant to say "before JDK-8176533".

Chris

On 11/28/18 10:11 AM, Chris Plummer wrote:
> Hi Gary,
>
> This seems reasonable. I just want clarification on one thing first. 
> Before JDK-8176828, it listed the suspend=y process, but could you do 
> anything with it? I'm assuming no, and therefore it makes sense not to 
> list it at all.
>
> thanks,
>
> Chris
>
> On 11/28/18 8:33 AM, Gary Adams wrote:
>> I'd like to close JDK-8176828 as will not fix.
>>   https://bugs.openjdk.java.net/browse/JDK-8176828
>>
>> This bug was originally thought to be associated with
>> a regression fix in JDK-8176533, but I believe there
>> is simply a misunderstanding of how the "suspend=y"
>> behavior is supported for the jdwp agent library.
>>
>> The "suspend=y" setting is designed to maximize the number
>> of events that can been seen by an attaching debugger.
>> This calls for the process to be waiting for the debugger connection
>> before the VM has been completely initialized.
>>
>> In particular, the thread.cpp create_vm() function causes the
>> debugInit.c initialize() function to start the transport connection
>> and wait for an external debugger to attach. Once the dt_socket 
>> connection
>> is established the create_vm() function will complete. It is the
>> processing of the create_vm_timer.end() that results in the
>> management.cpp record_vm_startup_time() and the
>> PerfMemory::set_accessible(true) to be set.
>>
>> Without the accessible field being set an external program can not use
>> the PerfMemory. That is why "jcmd -l" passes over processes which
>> do not have an initialized VM running.
>>
>> =====
>> src/hotspot/share/runtime/:
>> src/jdk.jdwp.agent/share/native/libjdwp/:
>>
>>   thread.cpp:3587:jint Threads::create_vm(JavaVMInitArgs* args, bool* 
>> canTryAgain) {
>>   ...
>>   thread.cpp:3610:  create_vm_timer.start();
>>   ...
>>   thread.cpp:3907:  JvmtiExport::post_vm_initialized();
>>   ...
>>     debugInit.c:432:cbEarlyVMInit(jvmtiEnv *jvmti_env, JNIEnv *env, 
>> jthread thread)
>>     ...
>>     debugInit.c:103:static void initialize(JNIEnv *env, jthread 
>> thread, EventIndex triggering_ei);
>>     ...
>>     debugInit.c:732:    (void)bagEnumerateOver(transports, 
>> startTransport, &arg);
>>     ...
>>     debugInit.c:751:    transport_waitForConnection();
>>   ...
>>   thread.cpp:3955:  create_vm_timer.end();
>>
>> ====
>> src/hotspot/share/services/management.cpp:
>>
>>    203  void Management::record_vm_startup_time(jlong begin, jlong 
>> duration) {
>>    204    // if the performance counter is not initialized,
>>    205    // then vm initialization failed; simply return.
>>    206    if (_begin_vm_creation_time == NULL) return;
>>    207
>>    208    _begin_vm_creation_time->set_value(begin);
>>    209    _end_vm_creation_time->set_value(begin + duration);
>>    210    PerfMemory::set_accessible(true);
>>    211  }
>>
>>
>
>