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diff src/share/vm/gc_implementation/g1/concurrentMarkThread.hpp @ 1359:23b1b27ac76c

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6909756: G1: guarantee(G1CollectedHeap::heap()->mark_in_progress(),"Precondition.") Summary: Make sure that two marking cycles do not overlap, i.e., a new one can only start after the concurrent marking thread finishes all its work. In the fix I piggy-back a couple of minor extra fixes: some general code reformatting for consistency (only around the code I modified), the removal of a field (G1CollectorPolicy::_should_initiate_conc_mark) which doesn't seem to be used at all (it's only set but never read), as well as moving the "is GC locker active" test earlier into the G1 pause / Full GC and using a more appropriate method for it. Reviewed-by: johnc, jmasa, jcoomes, ysr
author tonyp
date Tue, 06 Apr 2010 10:59:45 -0400
parents 035d2e036a9b
children c18cbe5936b8
line wrap: on
line diff
--- a/src/share/vm/gc_implementation/g1/concurrentMarkThread.hpp	Mon Apr 05 12:19:22 2010 -0400
+++ b/src/share/vm/gc_implementation/g1/concurrentMarkThread.hpp	Tue Apr 06 10:59:45 2010 -0400
@@ -42,8 +42,8 @@
 
  private:
   ConcurrentMark*                  _cm;
-  bool                             _started;
-  bool                             _in_progress;
+  volatile bool                    _started;
+  volatile bool                    _in_progress;
 
   void sleepBeforeNextCycle();
 
@@ -67,15 +67,25 @@
   // Counting virtual time so far.
   double vtime_count_accum() { return _vtime_count_accum; }
 
-  ConcurrentMark* cm()                           { return _cm;     }
+  ConcurrentMark* cm()     { return _cm; }
+
+  void set_started()       { _started = true;  }
+  void clear_started()     { _started = false; }
+  bool started()           { return _started;  }
+
+  void set_in_progress()   { _in_progress = true;  }
+  void clear_in_progress() { _in_progress = false; }
+  bool in_progress()       { return _in_progress;  }
 
-  void            set_started()                  { _started = true;   }
-  void            clear_started()                { _started = false;  }
-  bool            started()                      { return _started;   }
-
-  void            set_in_progress()              { _in_progress = true;   }
-  void            clear_in_progress()            { _in_progress = false;  }
-  bool            in_progress()                  { return _in_progress;   }
+  // This flag returns true from the moment a marking cycle is
+  // initiated (during the initial-mark pause when started() is set)
+  // to the moment when the cycle completes (just after the next
+  // marking bitmap has been cleared and in_progress() is
+  // cleared). While this flag is true we will not start another cycle
+  // so that cycles do not overlap. We cannot use just in_progress()
+  // as the CM thread might take some time to wake up before noticing
+  // that started() is set and set in_progress().
+  bool during_cycle()      { return started() || in_progress(); }
 
   // Yield for GC
   void            yield();