8268855: Cleanup name handling in the Thread class and subclasses

Reviewed-by: lfoltan, coleenp

src/hotspot/cpu/aarch64/gc/shared/barrierSetNMethod_aarch64.cpp

@@ -116,7 +116,7 @@ void BarrierSetNMethod::deoptimize(nmethod* nm, address* return_address_ptr) {
     log_trace(nmethod, barrier)("deoptimize(nmethod: %s(%p), return_addr: %p, osr: %d, thread: %p(%s), making rsp: %p) -> %p",
                                 nm->method()->name_and_sig_as_C_string(),
                                 nm, *(address *) return_address_ptr, nm->is_osr_method(), thread,
-                                thread->get_thread_name(), frame.sp(), nm->verified_entry_point());
+                                thread->name(), frame.sp(), nm->verified_entry_point());
   }
 
   new_frame->sp = frame.sp();

src/hotspot/cpu/x86/gc/shared/barrierSetNMethod_x86.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018, 2020, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2018, 2021, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -132,7 +132,7 @@ void BarrierSetNMethod::deoptimize(nmethod* nm, address* return_address_ptr) {
     ResourceMark mark;
     log_trace(nmethod, barrier)("deoptimize(nmethod: %p, return_addr: %p, osr: %d, thread: %p(%s), making rsp: %p) -> %p",
                                nm, (address *) return_address_ptr, nm->is_osr_method(), jth,
-                               jth->get_thread_name(), callers_rsp, nm->verified_entry_point());
+                               jth->name(), callers_rsp, nm->verified_entry_point());
   }
 
   assert(nm->frame_size() >= 3, "invariant");

src/hotspot/share/compiler/compileBroker.cpp

@@ -1008,9 +1008,9 @@ void CompileBroker::init_compiler_sweeper_threads() {
       _compilers[1]->set_num_compiler_threads(i + 1);
       if (TraceCompilerThreads) {
         ResourceMark rm;
-        ThreadsListHandle tlh;  // get_thread_name() depends on the TLH.
+        ThreadsListHandle tlh;  // name() depends on the TLH.
         assert(tlh.includes(ct), "ct=" INTPTR_FORMAT " exited unexpectedly.", p2i(ct));
-        tty->print_cr("Added initial compiler thread %s", ct->get_thread_name());
+        tty->print_cr("Added initial compiler thread %s", ct->name());
       }
     }
   }
@@ -1029,9 +1029,9 @@ void CompileBroker::init_compiler_sweeper_threads() {
       _compilers[0]->set_num_compiler_threads(i + 1);
       if (TraceCompilerThreads) {
         ResourceMark rm;
-        ThreadsListHandle tlh;  // get_thread_name() depends on the TLH.
+        ThreadsListHandle tlh;  // name() depends on the TLH.
         assert(tlh.includes(ct), "ct=" INTPTR_FORMAT " exited unexpectedly.", p2i(ct));
-        tty->print_cr("Added initial compiler thread %s", ct->get_thread_name());
+        tty->print_cr("Added initial compiler thread %s", ct->name());
       }
     }
   }
@@ -1116,10 +1116,10 @@ void CompileBroker::possibly_add_compiler_threads(JavaThread* THREAD) {
       _compilers[1]->set_num_compiler_threads(i + 1);
       if (TraceCompilerThreads) {
         ResourceMark rm;
-        ThreadsListHandle tlh;  // get_thread_name() depends on the TLH.
+        ThreadsListHandle tlh;  // name() depends on the TLH.
         assert(tlh.includes(ct), "ct=" INTPTR_FORMAT " exited unexpectedly.", p2i(ct));
         tty->print_cr("Added compiler thread %s (available memory: %dMB, available non-profiled code cache: %dMB)",
-                      ct->get_thread_name(), (int)(available_memory/M), (int)(available_cc_np/M));
+                      ct->name(), (int)(available_memory/M), (int)(available_cc_np/M));
       }
     }
   }
@@ -1137,10 +1137,10 @@ void CompileBroker::possibly_add_compiler_threads(JavaThread* THREAD) {
       _compilers[0]->set_num_compiler_threads(i + 1);
       if (TraceCompilerThreads) {
         ResourceMark rm;
-        ThreadsListHandle tlh;  // get_thread_name() depends on the TLH.
+        ThreadsListHandle tlh;  // name() depends on the TLH.
         assert(tlh.includes(ct), "ct=" INTPTR_FORMAT " exited unexpectedly.", p2i(ct));
         tty->print_cr("Added compiler thread %s (available memory: %dMB, available profiled code cache: %dMB)",
-                      ct->get_thread_name(), (int)(available_memory/M), (int)(available_cc_p/M));
+                      ct->name(), (int)(available_memory/M), (int)(available_cc_p/M));
       }
     }
   }

src/hotspot/share/gc/shared/concurrentGCThread.hpp

@@ -49,6 +49,9 @@ public:
 
   bool should_terminate() const;
   bool has_terminated() const;
+
+  // Printing
+  const char* type_name() const { return "ConcurrentGCThread"; }
 };
 
 #endif // SHARE_GC_SHARED_CONCURRENTGCTHREAD_HPP

src/hotspot/share/gc/shared/workgroup.hpp

@@ -219,6 +219,9 @@ public:
   // Predicate for Thread
   bool is_GC_task_thread() const override { return gang()->are_GC_task_threads(); }
   bool is_ConcurrentGC_thread() const override { return gang()->are_ConcurrentGC_threads(); }
+
+  // Printing
+  const char* type_name() const override { return "GCTaskThread"; }
 };
 
 // A class that acts as a synchronisation barrier. Workers enter

src/hotspot/share/gc/shenandoah/shenandoahControlThread.hpp

@@ -143,7 +143,7 @@ public:
   void prepare_for_graceful_shutdown();
   bool in_graceful_shutdown();
 
-  char* name() const { return (char*)"ShenandoahControlThread";}
+  const char* name() const { return "ShenandoahControlThread";}
 
   // Printing
   void print_on(outputStream* st) const;

src/hotspot/share/jfr/periodic/sampling/jfrThreadSampler.cpp

@@ -343,7 +343,8 @@ class JfrThreadSampler : public NonJavaThread {
  protected:
   virtual void post_run();
  public:
-  virtual char* name() const { return (char*)"JFR Thread Sampler"; }
+  virtual const char* name() const { return "JFR Thread Sampler"; }
+  virtual const char* type_name() const { return "JfrThreadSampler"; }
   bool is_JfrSampler_thread() const { return true; }
   void run();
   static Monitor* transition_block() { return JfrThreadSampler_lock; }

src/hotspot/share/jvmci/jvmciCompilerToVM.cpp

@@ -2279,7 +2279,7 @@ C2V_VMENTRY_PREFIX(jboolean, attachCurrentThread, (JNIEnv* env, jobject c2vm, jb
 
     JavaVMAttachArgs attach_args;
     attach_args.version = JNI_VERSION_1_2;
-    attach_args.name = thread->name();
+    attach_args.name = const_cast<char*>(thread->name());
     attach_args.group = NULL;
     JNIEnv* peerJNIEnv;
     if (runtime->GetEnv(thread, (void**) &peerJNIEnv, JNI_VERSION_1_2) == JNI_OK) {

src/hotspot/share/jvmci/jvmciEnv.cpp

@@ -205,7 +205,7 @@ void JVMCIEnv::init_env_mode_runtime(JavaThread* thread, JNIEnv* parent_env) {
       ResourceMark rm; // Thread name is resource allocated
       JavaVMAttachArgs attach_args;
       attach_args.version = JNI_VERSION_1_2;
-      attach_args.name = thread->name();
+      attach_args.name = const_cast<char*>(thread->name());
       attach_args.group = NULL;
       if (_runtime->AttachCurrentThread(thread, (void**) &_env, &attach_args) != JNI_OK) {
         fatal("Error attaching current thread (%s) to JVMCI shared library JNI interface", attach_args.name);

src/hotspot/share/logging/logAsyncWriter.hpp

@@ -160,7 +160,8 @@ class AsyncLogWriter : public NonJavaThread {
     NonJavaThread::pre_run();
     log_debug(logging, thread)("starting AsyncLog Thread tid = " INTX_FORMAT, os::current_thread_id());
   }
-  char* name() const override { return (char*)"AsyncLog Thread"; }
+  const char* name() const override { return "AsyncLog Thread"; }
+  const char* type_name() const override { return "AsyncLogWriter"; }
   void print_on(outputStream* st) const override {
     st->print("\"%s\" ", name());
     Thread::print_on(st);

src/hotspot/share/prims/jni.cpp

@@ -576,7 +576,7 @@ JNI_ENTRY_NO_PRESERVE(void, jni_ExceptionDescribe(JNIEnv *env))
       if (thread != NULL && thread->threadObj() != NULL) {
         ResourceMark rm(THREAD);
         jio_fprintf(defaultStream::error_stream(),
-        "in thread \"%s\" ", thread->get_thread_name());
+        "in thread \"%s\" ", thread->name());
       }
       if (ex->is_a(vmClasses::Throwable_klass())) {
         JavaValue result(T_VOID);

src/hotspot/share/runtime/nonJavaThread.hpp

@@ -70,8 +70,10 @@ public:
   void step();
 };
 
-// Name support for threads.  non-JavaThread subclasses with multiple
+// A base class for non-JavaThread subclasses with multiple
-// uniquely named instances should derive from this.
+// uniquely named instances. NamedThreads also provide a common
+// location to store GC information needed by GC threads
+// and the VMThread.
 class NamedThread: public NonJavaThread {
   friend class VMStructs;
   enum {
@@ -89,7 +91,8 @@ class NamedThread: public NonJavaThread {
   // May only be called once per thread.
   void set_name(const char* format, ...)  ATTRIBUTE_PRINTF(2, 3);
   virtual bool is_Named_thread() const { return true; }
-  virtual char* name() const { return _name == NULL ? (char*)"Unknown Thread" : _name; }
+  virtual const char* name() const { return _name == NULL ? "Unknown Thread" : _name; }
+  virtual const char* type_name() const { return "NamedThread"; }
   Thread *processed_thread() { return _processed_thread; }
   void set_processed_thread(Thread *thread) { _processed_thread = thread; }
   virtual void print_on(outputStream* st) const;
@@ -117,6 +120,10 @@ class WorkerThread: public NamedThread {
 
   void set_id(uint work_id)             { _id = work_id; }
   uint id() const                       { return _id; }
+
+  // Printing
+  virtual const char* type_name() const { return "WorkerThread"; }
+
 };
 
 // A single WatcherThread is used for simulating timer interrupts.
@@ -132,6 +139,7 @@ class WatcherThread: public NonJavaThread {
   // volatile due to at least one lock-free read
   volatile static bool _should_terminate;
  public:
+
   enum SomeConstants {
     delay_interval = 10                          // interrupt delay in milliseconds
   };
@@ -148,7 +156,8 @@ class WatcherThread: public NonJavaThread {
   bool is_Watcher_thread() const                 { return true; }
 
   // Printing
-  char* name() const { return (char*)"VM Periodic Task Thread"; }
+  const char* name() const { return "VM Periodic Task Thread"; }
+  const char* type_name() const { return "WatcherThread"; }
   void print_on(outputStream* st) const;
   void unpark();
 

src/hotspot/share/runtime/thread.cpp

@@ -162,7 +162,7 @@ void universe_post_module_init();  // must happen after call_initPhase2
     {                                                                      \
       ResourceMark rm(this);                                               \
       int len = 0;                                                         \
-      const char* name = (javathread)->get_thread_name();                  \
+      const char* name = (javathread)->name();                             \
       len = strlen(name);                                                  \
       HOTSPOT_THREAD_PROBE_##probe(/* probe = start, stop */               \
         (char *) name, len,                                                \
@@ -609,17 +609,7 @@ void Thread::print() const { print_on(tty); }
 void Thread::print_on_error(outputStream* st, char* buf, int buflen) const {
   assert(!(is_Compiler_thread() || is_Java_thread()), "Can't call name() here if it allocates");
 
-  if (is_VM_thread())                 { st->print("VMThread"); }
+  st->print("%s \"%s\"", type_name(), name());
-  else if (is_GC_task_thread())       { st->print("GCTaskThread"); }
-  else if (is_Watcher_thread())       { st->print("WatcherThread"); }
-  else if (is_ConcurrentGC_thread())  { st->print("ConcurrentGCThread"); }
-  else if (this == AsyncLogWriter::instance()) {
-    st->print("%s", this->name());
-  } else                                { st->print("Thread"); }
-
-  if (is_Named_thread()) {
-    st->print(" \"%s\"", name());
-  }
 
   OSThread* os_thr = osthread();
   if (os_thr != NULL) {
@@ -1272,7 +1262,7 @@ void JavaThread::thread_main_inner() {
       !java_lang_Thread::is_stillborn(this->threadObj())) {
     {
       ResourceMark rm(this);
-      this->set_native_thread_name(this->get_thread_name());
+      this->set_native_thread_name(this->name());
     }
     HandleMark hm(this);
     this->entry_point()(this, this);
@@ -1351,7 +1341,7 @@ void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
                     "\nException: %s thrown from the UncaughtExceptionHandler"
                     " in thread \"%s\"\n",
                     pending_exception()->klass()->external_name(),
-                    get_thread_name());
+                    name());
         CLEAR_PENDING_EXCEPTION;
       }
     }
@@ -1456,7 +1446,7 @@ void JavaThread::exit(bool destroy_vm, ExitType exit_type) {
   char* thread_name = NULL;
   if (log_is_enabled(Debug, os, thread, timer)) {
     ResourceMark rm(this);
-    thread_name = os::strdup(get_thread_name());
+    thread_name = os::strdup(name());
   }
 
   log_info(os, thread)("JavaThread %s (tid: " UINTX_FORMAT ").",
@@ -2053,7 +2043,7 @@ void JavaThread::print_thread_state_on(outputStream *st) const {
 // Called by Threads::print() for VM_PrintThreads operation
 void JavaThread::print_on(outputStream *st, bool print_extended_info) const {
   st->print_raw("\"");
-  st->print_raw(get_thread_name());
+  st->print_raw(name());
   st->print_raw("\" ");
   oop thread_oop = threadObj();
   if (thread_oop != NULL) {
@@ -2091,7 +2081,7 @@ void JavaThread::print_name_on_error(outputStream* st, char *buf, int buflen) co
 // Called by fatal error handler. The difference between this and
 // JavaThread::print() is that we can't grab lock or allocate memory.
 void JavaThread::print_on_error(outputStream* st, char *buf, int buflen) const {
-  st->print("JavaThread \"%s\"", get_thread_name_string(buf, buflen));
+  st->print("%s \"%s\"", type_name(), get_thread_name_string(buf, buflen));
   oop thread_obj = threadObj();
   if (thread_obj != NULL) {
     if (java_lang_Thread::is_daemon(thread_obj)) st->print(" daemon");
@@ -2139,7 +2129,7 @@ void JavaThread::verify() {
 // seen prior to having its threadObj set (e.g., JNI attaching threads and
 // if vm exit occurs during initialization). These cases can all be accounted
 // for such that this method never returns NULL.
-const char* JavaThread::get_thread_name() const {
+const char* JavaThread::name() const  {
   if (Thread::is_JavaThread_protected(this)) {
     // The target JavaThread is protected so get_thread_name_string() is safe:
     return get_thread_name_string();
@@ -2165,7 +2155,7 @@ const char* JavaThread::get_thread_name_string(char* buf, int buflen) const {
     } else if (is_attaching_via_jni()) { // workaround for 6412693 - see 6404306
       name_str = "<no-name - thread is attaching>";
     } else {
-      name_str = Thread::name();
+      name_str = "<un-named>";
     }
   } else {
     name_str = Thread::name();

src/hotspot/share/runtime/thread.hpp

@@ -352,7 +352,15 @@ class Thread: public ThreadShadow {
   // If so it must participate in the safepoint protocol.
   virtual bool is_active_Java_thread() const         { return false; }
 
-  virtual char* name() const { return (char*)"Unknown thread"; }
+  // All threads are given names. For singleton subclasses we can
+  // just hard-wire the known name of the instance. JavaThreads and
+  // NamedThreads support multiple named instances, and dynamic
+  // changing of the name of an instance.
+  virtual const char* name() const { return "Unknown thread"; }
+
+  // A thread's type name is also made available for debugging
+  // and logging.
+  virtual const char* type_name() const { return "Thread"; }
 
   // Returns the current thread (ASSERTS if NULL)
   static inline Thread* current();
@@ -568,6 +576,7 @@ protected:
   virtual void print_on(outputStream* st) const { print_on(st, false); }
   void print() const;
   virtual void print_on_error(outputStream* st, char* buf, int buflen) const;
+  // Basic, non-virtual, printing support that is simple and always safe.
   void print_value_on(outputStream* st) const;
 
   // Debug-only code
@@ -1347,6 +1356,9 @@ class JavaThread: public Thread {
  private:
   void set_entry_point(ThreadFunction entry_point) { _entry_point = entry_point; }
 
+  // factor out low-level mechanics for use in both normal and error cases
+  const char* get_thread_name_string(char* buf = NULL, int buflen = 0) const;
+
  public:
 
   // Frame iteration; calls the function f for all frames on the stack
@@ -1366,7 +1378,9 @@ class JavaThread: public Thread {
   DEBUG_ONLY(void verify_states_for_handshake();)
 
   // Misc. operations
-  char* name() const { return (char*)get_thread_name(); }
+  const char* name() const;
+  const char* type_name() const { return "JavaThread"; }
+
   void print_on(outputStream* st, bool print_extended_info) const;
   void print_on(outputStream* st) const { print_on(st, false); }
   void print() const;
@@ -1374,11 +1388,7 @@ class JavaThread: public Thread {
   void print_on_error(outputStream* st, char* buf, int buflen) const;
   void print_name_on_error(outputStream* st, char* buf, int buflen) const;
   void verify();
-  const char* get_thread_name() const;
+
- protected:
-  // factor out low-level mechanics for use in both normal and error cases
-  virtual const char* get_thread_name_string(char* buf = NULL, int buflen = 0) const;
- public:
   // Accessing frames
   frame last_frame() {
     _anchor.make_walkable(this);

src/hotspot/share/runtime/vmThread.hpp

@@ -130,6 +130,9 @@ class VMThread: public NamedThread {
 
   static void wait_until_executed(VM_Operation* op);
 
+  // Printing
+  const char* type_name() const { return "VMThread"; }
+
  private:
   // VM_Operation support
   static VM_Operation*     _cur_vm_operation;   // Current VM operation

src/hotspot/share/services/threadService.cpp

@@ -975,7 +975,7 @@ void DeadlockCycle::print_on_with(ThreadsList * t_list, outputStream* st) const
     waitingToLockRawMonitor = currentThread->current_pending_raw_monitor();
     waitingToLockBlocker = currentThread->current_park_blocker();
     st->cr();
-    st->print_cr("\"%s\":", currentThread->get_thread_name());
+    st->print_cr("\"%s\":", currentThread->name());
     const char* owner_desc = ",\n  which is held by";
 
     // Note: As the JVM TI "monitor contended enter" event callback is executed after ObjectMonitor
@@ -987,7 +987,7 @@ void DeadlockCycle::print_on_with(ThreadsList * t_list, outputStream* st) const
       if (owner != NULL) {
         if (owner->is_Java_thread()) {
           currentThread = JavaThread::cast(owner);
-          st->print_cr("%s \"%s\"", owner_desc, currentThread->get_thread_name());
+          st->print_cr("%s \"%s\"", owner_desc, currentThread->name());
         } else {
           st->print_cr(",\n  which has now been released");
         }
@@ -1026,7 +1026,7 @@ void DeadlockCycle::print_on_with(ThreadsList * t_list, outputStream* st) const
       currentThread = java_lang_Thread::thread(ownerObj);
       assert(currentThread != NULL, "AbstractOwnableSynchronizer owning thread is unexpectedly NULL");
     }
-    st->print_cr("%s \"%s\"", owner_desc, currentThread->get_thread_name());
+    st->print_cr("%s \"%s\"", owner_desc, currentThread->name());
   }
 
   st->cr();
@@ -1038,7 +1038,7 @@ void DeadlockCycle::print_on_with(ThreadsList * t_list, outputStream* st) const
   st->print_cr("===================================================");
   for (int j = 0; j < len; j++) {
     currentThread = _threads->at(j);
-    st->print_cr("\"%s\":", currentThread->get_thread_name());
+    st->print_cr("\"%s\":", currentThread->name());
     currentThread->print_stack_on(st);
   }
   JavaMonitorsInStackTrace = oldJavaMonitorsInStackTrace;