diff -r 85cf92183e39 -r 99e5a8f5d81f hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp
--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Mon Apr 05 12:19:22 2010 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp	Tue Apr 06 10:59:45 2010 -0400
@@ -902,6 +902,10 @@
 
 void G1CollectedHeap::do_collection(bool full, bool clear_all_soft_refs,
                                     size_t word_size) {
+  if (GC_locker::check_active_before_gc()) {
+    return; // GC is disabled (e.g. JNI GetXXXCritical operation)
+  }
+
   ResourceMark rm;
 
   if (PrintHeapAtGC) {
@@ -916,10 +920,6 @@
   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
   assert(Thread::current() == VMThread::vm_thread(), "should be in vm thread");
 
-  if (GC_locker::is_active()) {
-    return; // GC is disabled (e.g. JNI GetXXXCritical operation)
-  }
-
   {
     IsGCActiveMark x;
 
@@ -2658,6 +2658,10 @@
 
 void
 G1CollectedHeap::do_collection_pause_at_safepoint() {
+  if (GC_locker::check_active_before_gc()) {
+    return; // GC is disabled (e.g. JNI GetXXXCritical operation)
+  }
+
   if (PrintHeapAtGC) {
     Universe::print_heap_before_gc();
   }
@@ -2665,6 +2669,11 @@
   {
     ResourceMark rm;
 
+    // This call will decide whether this pause is an initial-mark
+    // pause. If it is, during_initial_mark_pause() will return true
+    // for the duration of this pause.
+    g1_policy()->decide_on_conc_mark_initiation();
+
     char verbose_str[128];
     sprintf(verbose_str, "GC pause ");
     if (g1_policy()->in_young_gc_mode()) {
@@ -2673,7 +2682,7 @@
       else
         strcat(verbose_str, "(partial)");
     }
-    if (g1_policy()->should_initiate_conc_mark())
+    if (g1_policy()->during_initial_mark_pause())
       strcat(verbose_str, " (initial-mark)");
 
     // if PrintGCDetails is on, we'll print long statistics information
@@ -2697,10 +2706,6 @@
              "young list should be well formed");
     }
 
-    if (GC_locker::is_active()) {
-      return; // GC is disabled (e.g. JNI GetXXXCritical operation)
-    }
-
     bool abandoned = false;
     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
       IsGCActiveMark x;
@@ -2756,7 +2761,7 @@
       _young_list->print();
 #endif // SCAN_ONLY_VERBOSE
 
-      if (g1_policy()->should_initiate_conc_mark()) {
+      if (g1_policy()->during_initial_mark_pause()) {
         concurrent_mark()->checkpointRootsInitialPre();
       }
       save_marks();
@@ -2858,7 +2863,7 @@
       }
 
       if (g1_policy()->in_young_gc_mode() &&
-          g1_policy()->should_initiate_conc_mark()) {
+          g1_policy()->during_initial_mark_pause()) {
         concurrent_mark()->checkpointRootsInitialPost();
         set_marking_started();
         // CAUTION: after the doConcurrentMark() call below,
@@ -3977,7 +3982,7 @@
     OopsInHeapRegionClosure        *scan_perm_cl;
     OopsInHeapRegionClosure        *scan_so_cl;
 
-    if (_g1h->g1_policy()->should_initiate_conc_mark()) {
+    if (_g1h->g1_policy()->during_initial_mark_pause()) {
       scan_root_cl = &scan_mark_root_cl;
       scan_perm_cl = &scan_mark_perm_cl;
       scan_so_cl   = &scan_mark_heap_rs_cl;
@@ -4140,7 +4145,7 @@
   FilterAndMarkInHeapRegionAndIntoCSClosure scan_and_mark(this, &boc, concurrent_mark());
 
   OopsInHeapRegionClosure *foc;
-  if (g1_policy()->should_initiate_conc_mark())
+  if (g1_policy()->during_initial_mark_pause())
     foc = &scan_and_mark;
   else
     foc = &scan_only;