6980838: G1: guarantee(false) failed: thread has an unexpected active value in its SATB queue Summary: Under certain circumstances a safepoint could happen between a JavaThread object being created and that object being added to the Java threads list. This could cause the active field of that thread's SATB queue to get out-of-sync with respect to the other Java threads. The solution is to activate the SATB queue, when necessary, before adding the thread to the Java threads list, not when the JavaThread object is created. The changeset also includes a small fix to rename the surrogate locker thread from "Surrogate Locker Thread (CMS)" to "Surrogate Locker Thread (Concurrent GC)" since it's also used in G1. Reviewed-by: iveresov, ysr, johnc, jcoomes

--- a/src/share/vm/gc_implementation/g1/ptrQueue.hpp	Fri Oct 01 21:48:40 2010 -0700
+++ b/src/share/vm/gc_implementation/g1/ptrQueue.hpp	Fri Oct 01 16:43:05 2010 -0400
@@ -89,6 +89,10 @@
     return _buf == NULL ? 0 : _sz - _index;
   }
 
+  bool is_empty() {
+    return _buf == NULL || _sz == _index;
+  }
+
   // Set the "active" property of the queue to "b".  An enqueue to an
   // inactive thread is a no-op.  Setting a queue to inactive resets its
   // log to the empty state.