8258837: Remove JVM option DisableStartThread

Reviewed-by: kbarrett, dcubed

Author: Harold Seigel

src/hotspot/share/runtime/globals.hpp

@@ -697,10 +697,6 @@ const intx ObjectAlignmentInBytes = 8;
  product(bool, ClassUnloadingWithConcurrentMark, true, \
  "Do unloading of classes with a concurrent marking cycle") \
  \
- develop(bool, DisableStartThread, false, \
- "Disable starting of additional Java threads " \
- "(for debugging only)") \
- \
  develop(bool, MemProfiling, false, \
  "Write memory usage profiling to log file") \
  \
@@ -2079,7 +2075,7 @@ const intx ObjectAlignmentInBytes = 8;
  constraint(InitArrayShortSizeConstraintFunc, AfterErgo) \
  \
  product(ccstr, AllocateHeapAt, NULL, \
- "Path to the directoy where a temporary file will be created "  \
+ "Path to the directory where a temporary file will be created " \
  "to use as the backing store for Java Heap.") \
  \
  develop(int, VerifyMetaspaceInterval, DEBUG_ONLY(500) NOT_DEBUG(0), \

src/hotspot/share/runtime/thread.cpp

@@ -495,17 +495,15 @@ void Thread::set_priority(Thread* thread, ThreadPriority priority) {
 void Thread::start(Thread* thread) {
  // Start is different from resume in that its safety is guaranteed by context or
  // being called from a Java method synchronized on the Thread object.
- if (!DisableStartThread) {
- if (thread->is_Java_thread()) {
- // Initialize the thread state to RUNNABLE before starting this thread.
- // Can not set it after the thread started because we do not know the
- // exact thread state at that time. It could be in MONITOR_WAIT or
- // in SLEEPING or some other state.
- java_lang_Thread::set_thread_status(thread->as_Java_thread()->threadObj(),
- JavaThreadStatus::RUNNABLE);
- }
- os::start_thread(thread);
+ if (thread->is_Java_thread()) {
+ // Initialize the thread state to RUNNABLE before starting this thread.
+ // Can not set it after the thread started because we do not know the
+ // exact thread state at that time. It could be in MONITOR_WAIT or
+ // in SLEEPING or some other state.
+ java_lang_Thread::set_thread_status(thread->as_Java_thread()->threadObj(),
+ JavaThreadStatus::RUNNABLE);
  }
+ os::start_thread(thread);
 }
 
 class InstallAsyncExceptionClosure : public HandshakeClosure {
@@ -1230,9 +1228,7 @@ WatcherThread::WatcherThread() : NonJavaThread() {
  // If the VMThread's priority is not lower than the WatcherThread profiling
  // will be inaccurate.
  os::set_priority(this, MaxPriority);
- if (!DisableStartThread) {
- os::start_thread(this);
- }
+ os::start_thread(this);
  }
 }