src/hotspot/share/runtime/objectMonitor.hpp

rev 55489 : Checkpoint latest preliminary review patches for full OpenJDK review; merge with 8222295.patch.
rev 55490 : imported patch dcubed.monitor_deflate_conc.v2.01
rev 55492 : imported patch dcubed.monitor_deflate_conc.v2.03
rev 55494 : imported patch dcubed.monitor_deflate_conc.v2.05

@@ -134,10 +134,11 @@
     OM_INTERRUPTED,           // Thread.interrupt()
     OM_TIMED_OUT              // Object.wait() timed out
   };
 
  private:
+  friend class ObjectMonitorHandle;
   friend class ObjectSynchronizer;
   friend class ObjectWaiter;
   friend class VMStructs;
   JVMCI_ONLY(friend class JVMCIVMStructs;)
 

@@ -148,10 +149,12 @@
  private:
   DEFINE_PAD_MINUS_SIZE(0, DEFAULT_CACHE_LINE_SIZE,
                         sizeof(volatile markOop) + sizeof(void * volatile) +
                         sizeof(ObjectMonitor *));
  protected:                         // protected for JvmtiRawMonitor
+  // Used by async deflation as a marker in the _owner field:
+  #define DEFLATER_MARKER reinterpret_cast<void*>(-1)
   void *  volatile _owner;          // pointer to owning thread OR BasicLock
   volatile jlong _previous_owner_tid;  // thread id of the previous owner of the monitor
   volatile intptr_t  _recursions;   // recursion count, 0 for first entry
   ObjectWaiter * volatile _EntryList; // Threads blocked on entry or reentry.
                                       // The list is actually composed of WaitNodes,

@@ -164,16 +167,25 @@
   volatile int _Spinner;            // for exit->spinner handoff optimization
   volatile int _SpinDuration;
 
   volatile jint  _contentions;      // Number of active contentions in enter(). It is used by is_busy()
                                     // along with other fields to determine if an ObjectMonitor can be
-                                    // deflated. See ObjectSynchronizer::deflate_monitor().
+                                    // deflated. See ObjectSynchronizer::deflate_monitor() and
+                                    // ObjectSynchronizer::deflate_monitor_using_JT().
  protected:
   ObjectWaiter * volatile _WaitSet; // LL of threads wait()ing on the monitor
   volatile jint  _waiters;          // number of waiting threads
  private:
   volatile int _WaitSetLock;        // protects Wait Queue - simple spinlock
+  volatile jint _ref_count;         // ref count for ObjectMonitor* and used by the async deflation
+                                    // protocol. See ObjectSynchronizer::deflate_monitor_using_JT().
+  typedef enum {
+    Free = 0,  // Free must be 0 for monitor to be free after memset(..,0,..).
+    New,
+    Old
+  } AllocationState;
+  AllocationState _allocation_state;
 
  public:
   static void Initialize();
 
   // Only perform a PerfData operation if the PerfData object has been

@@ -231,17 +243,31 @@
   volatile markOop* header_addr();
   void      set_header(markOop hdr);
 
   intptr_t is_busy() const {
     // TODO-FIXME: assert _owner == null implies _recursions = 0
-    return _contentions|_waiters|intptr_t(_owner)|intptr_t(_cxq)|intptr_t(_EntryList);
+    // We do not include _ref_count in the is_busy() check because
+    // _ref_count is for indicating that the ObjectMonitor* is in
+    // use which is orthogonal to whether the ObjectMonitor itself
+    // is in use for a locking operation.
+    intptr_t ret_code = _contentions | _waiters | intptr_t(_cxq) | intptr_t(_EntryList);
+    if (!AsyncDeflateIdleMonitors) {
+      ret_code |= intptr_t(_owner);
+    } else {
+      if (_owner != DEFLATER_MARKER) {
+        ret_code |= intptr_t(_owner);
+      }
+    }
+    return ret_code;
   }
   const char* is_busy_to_string(stringStream* ss);
 
   intptr_t  is_entered(Thread* current) const;
 
-  void*     owner() const;
+  void*     owner() const;  // Returns NULL if DEFLATER_MARKER is observed.
+  // Returns true if owner field == DEFLATER_MARKER and false otherwise.
+  bool      owner_is_DEFLATER_MARKER();
   void      set_owner(void* owner);
 
   jint      waiters() const;
 
   jint      contentions() const;

@@ -282,14 +308,24 @@
  public:
 
   void*     object() const;
   void*     object_addr();
   void      set_object(void* obj);
+  void      set_allocation_state(AllocationState s);
+  AllocationState allocation_state() const;
+  bool      is_free() const;
+  bool      is_active() const;
+  bool      is_old() const;
+  bool      is_new() const;
+  void      dec_ref_count();
+  void      inc_ref_count();
+  jint      ref_count() const;
 
   bool      check(TRAPS);       // true if the thread owns the monitor.
   void      check_slow(TRAPS);
   void      clear();
+  void      clear_using_JT();
 
   void      enter(TRAPS);
   void      exit(bool not_suspended, TRAPS);
   void      wait(jlong millis, bool interruptable, TRAPS);
   void      notify(TRAPS);

@@ -313,8 +349,40 @@
   int       TryLock(Thread * Self);
   int       NotRunnable(Thread * Self, Thread * Owner);
   int       TrySpin(Thread * Self);
   void      ExitEpilog(Thread * Self, ObjectWaiter * Wakee);
   bool      ExitSuspendEquivalent(JavaThread * Self);
+  void      install_displaced_markword_in_object(const oop obj);
 };
 
+// A helper object for managing an ObjectMonitor*'s ref_count. There
+// are special safety considerations when async deflation is used.
+class ObjectMonitorHandle : public StackObj {
+ private:
+  ObjectMonitor * _om_ptr;
+ public:
+  ObjectMonitorHandle() { _om_ptr = NULL; }
+  ~ObjectMonitorHandle();
+
+  ObjectMonitor * om_ptr() const { return _om_ptr; }
+  // Save the ObjectMonitor* associated with the specified markOop and
+  // increment the ref_count.
+  bool save_om_ptr(oop object, markOop mark);
+
+  // For internal used by ObjectSynchronizer::monitors_iterate().
+  ObjectMonitorHandle(ObjectMonitor * _om_ptr);
+  // For internal use by ObjectSynchronizer::inflate().
+  void set_om_ptr(ObjectMonitor * om_ptr);
+};
+
+// Macro to use guarantee() for more strict AsyncDeflateIdleMonitors
+// checks and assert() otherwise.
+#define ADIM_guarantee(p, ...)       \
+  do {                               \
+    if (AsyncDeflateIdleMonitors) {  \
+      guarantee(p, __VA_ARGS__);     \
+    } else {                         \
+      assert(p, __VA_ARGS__);        \
+    }                                \
+  } while (0)
+
 #endif // SHARE_RUNTIME_OBJECTMONITOR_HPP