8024974: Incorrect use of GC_locker::is_active() Summary: SymbolTable and StringTable can make calls to GC_locker::is_active() outside a safepoint. This isn't safe because the GC_locker active state (lock count) is only updated at a safepoint and only remains valid as long as _needs_gc is true. However, outside a safepoint_needs_gc can change to false at any time, which makes it impossible to do a correct call to is_active() in that context. In this case these calls can just be removed since the input argument to basic_add() should never be on the heap and so there's no need to check the GC_locker state. This change also adjusts the assert() in is_active() to makes sure all calls to this function are always done under a safepoint. Reviewed-by: brutisso, dcubed Contributed-by: per.liden@oracle.com

--- a/src/share/vm/memory/gcLocker.hpp	Wed Sep 18 15:59:41 2013 +0200
+++ b/src/share/vm/memory/gcLocker.hpp	Fri Sep 20 10:53:28 2013 +0200
@@ -88,7 +88,7 @@
  public:
   // Accessors
   static bool is_active() {
-    assert(_needs_gc || SafepointSynchronize::is_at_safepoint(), "only read at safepoint");
+    assert(SafepointSynchronize::is_at_safepoint(), "only read at safepoint");
     return is_active_internal();
   }
   static bool needs_gc()       { return _needs_gc;                        }