src/hotspot/share/runtime/objectMonitor.cpp

rev 54572 : Checkpoint latest preliminary review patches for full OpenJDK review; merge with 8222295.patch.
rev 54573 : imported patch dcubed.monitor_deflate_conc.v2.01
rev 54574 : imported patch dcubed.monitor_deflate_conc.v2.02

@@ -2097,17 +2097,21 @@
   if (AsyncDeflateIdleMonitors) {
     // Race here if monitor is not owned! The above ref_count bump
     // will cause subsequent async deflation to skip it. However,
     // previous or concurrent async deflation is a race.
     if (om_ptr->_owner == DEFLATER_MARKER && om_ptr->_contentions <= 0) {
-      // Async deflation is in progress. Attempt to restore the
-      // header/dmw to the object's header so that we only retry once
-      // if the deflater thread happens to be slow.
+      // Async deflation is in progress.
+      if (om_ptr->ref_count() <= 0) {
+        // And our ref_count increment above lost the race to async
+        // deflation. Attempt to restore the header/dmw to the
+        // object's header so that we only retry once if the deflater
+        // thread happens to be slow.
       om_ptr->install_displaced_markword_in_object(object);
       om_ptr->dec_ref_count();
       return false;
     }
+    }
     // The ObjectMonitor could have been deflated and reused for
     // another object before we bumped the ref_count so make sure
     // our object still refers to this ObjectMonitor.
     const markOop tmp = object->mark();
     if (!tmp->has_monitor() || tmp->monitor() != om_ptr) {