557   assert(_starting_thread != nullptr, "invariant");
558   return t == _starting_thread;
559 }
560 #endif // ASSERT
561 
562 bool Thread::set_as_starting_thread(JavaThread* jt) {
563   assert(jt != nullptr, "invariant");
564   assert(_starting_thread == nullptr, "already initialized: "
565          "_starting_thread=" INTPTR_FORMAT, p2i(_starting_thread));
566   // NOTE: this must be called from Threads::create_vm().
567   DEBUG_ONLY(_starting_thread = jt;)
568   return os::create_main_thread(jt);
569 }
570 
571 // Ad-hoc mutual exclusion primitive: spin lock
572 //
573 // We employ a spin lock _only for low-contention, fixed-length
574 // short-duration critical sections where we're concerned
575 // about native mutex_t or HotSpot Mutex:: latency.
576 




577 void Thread::SpinAcquire(volatile int * adr) {
578   if (AtomicAccess::cmpxchg(adr, 0, 1) == 0) {
579     return;   // normal fast-path return
580   }
581 
582   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
583   int ctr = 0;
584   int Yields = 0;
585   for (;;) {
586     while (*adr != 0) {
587       ++ctr;
588       if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
589         if (Yields > 5) {
590           os::naked_short_sleep(1);
591         } else {
592           os::naked_yield();
593           ++Yields;
594         }
595       } else {
596         SpinPause();

557   assert(_starting_thread != nullptr, "invariant");
558   return t == _starting_thread;
559 }
560 #endif // ASSERT
561 
562 bool Thread::set_as_starting_thread(JavaThread* jt) {
563   assert(jt != nullptr, "invariant");
564   assert(_starting_thread == nullptr, "already initialized: "
565          "_starting_thread=" INTPTR_FORMAT, p2i(_starting_thread));
566   // NOTE: this must be called from Threads::create_vm().
567   DEBUG_ONLY(_starting_thread = jt;)
568   return os::create_main_thread(jt);
569 }
570 
571 // Ad-hoc mutual exclusion primitive: spin lock
572 //
573 // We employ a spin lock _only for low-contention, fixed-length
574 // short-duration critical sections where we're concerned
575 // about native mutex_t or HotSpot Mutex:: latency.
576 
577 bool Thread::TrySpinAcquire(volatile int * adr) {
578   return AtomicAccess::cmpxchg(adr, 0, 1) == 0;
579 }
580 
581 void Thread::SpinAcquire(volatile int * adr) {
582   if (AtomicAccess::cmpxchg(adr, 0, 1) == 0) {
583     return;   // normal fast-path return
584   }
585 
586   // Slow-path : We've encountered contention -- Spin/Yield/Block strategy.
587   int ctr = 0;
588   int Yields = 0;
589   for (;;) {
590     while (*adr != 0) {
591       ++ctr;
592       if ((ctr & 0xFFF) == 0 || !os::is_MP()) {
593         if (Yields > 5) {
594           os::naked_short_sleep(1);
595         } else {
596           os::naked_yield();
597           ++Yields;
598         }
599       } else {
600         SpinPause();