src/hotspot/share/runtime/objectMonitor.cpp

rev 57560 : imported patch 8236035.patch.cr0
rev 57561 : dholmes CR - rename simply_set_owner_from() -> set_owner_from() and simply_set_owner_from_BasicLock() -> set_owner_from_BasicLock(); rename release_clear_owner_with_barrier() -> release_clear_owner() and refactor barrier code back into the call sites.
rev 57562 : kbarrett CR - rearrange some loads of _owner field to be more efficient; clarify header comment for try_set_owner_from() declaration; make some loads of _owner field DEBUG_ONLY since they only exist for assert()'s; update related logging calls to use the existing function parameter instead.

@@ -858,13 +858,13 @@
 // then wake a thread unnecessarily. This is benign, and we've
 // structured the code so the windows are short and the frequency
 // of such futile wakups is low.
 
 void ObjectMonitor::exit(bool not_suspended, TRAPS) {
-  Thread * const Self = THREAD;
-  if (THREAD != _owner) {
-    void* cur = _owner;
+  Thread* const Self = THREAD;
+  void* cur = Atomic::load(&_owner);
+  if (THREAD != cur) {
     if (THREAD->is_lock_owned((address)cur)) {
       assert(_recursions == 0, "invariant");
       set_owner_from_BasicLock(cur, Self);  // Convert from BasicLock* to Thread*.
       _recursions = 0;
     } else {

@@ -1118,12 +1118,12 @@
   assert(Self->is_Java_thread(), "Must be Java thread!");
   JavaThread *jt = (JavaThread *)THREAD;
 
   assert(InitDone, "Unexpectedly not initialized");
 
-  if (THREAD != _owner) {
-    void* cur = _owner;
+  void* cur = Atomic::load(&_owner);
+  if (THREAD != cur) {
     if (THREAD->is_lock_owned((address)cur)) {
       assert(_recursions == 0, "internal state error");
       set_owner_from_BasicLock(cur, Self);  // Convert from BasicLock* to Thread*.
       _recursions = 0;
     }

@@ -1167,14 +1167,14 @@
 // Returns true if the specified thread owns the ObjectMonitor.
 // Otherwise returns false and throws IllegalMonitorStateException
 // (IMSE). If there is a pending exception and the specified thread
 // is not the owner, that exception will be replaced by the IMSE.
 bool ObjectMonitor::check_owner(Thread* THREAD) {
-  if (_owner == THREAD) {
+  void* cur = Atomic::load(&_owner);
+  if (cur == THREAD) {
     return true;
   }
-  void* cur = _owner;
   if (THREAD->is_lock_owned((address)cur)) {
     set_owner_from_BasicLock(cur, THREAD);  // Convert from BasicLock* to Thread*.
     _recursions = 0;
     return true;
   }