The sweeper thread should not write the page flags. Added a sweeping complete phase, where the main…

src/spaces.h

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 439 matching lines @@
   // Set or clear multiple flags at a time. The flags in the mask
   // are set to the value in "flags", the rest retain the current value
   // in flags_.
   void SetFlags(intptr_t flags, intptr_t mask) {
     flags_ = (flags_ & ~mask) | (flags & mask);
   }
 
   // Return all current flags.
   intptr_t GetFlags() { return flags_; }
 
-  intptr_t parallel_sweeping() const {
-    return parallel_sweeping_;
+
+  // PARALLEL_SWEEPING_PENDING - This page is ready for parallel sweeping.
+  // PARALLEL_SWEEPING_IN_PROGRESS - This page is currently swept or was
+  // swept by a sweeper thread.
+  // PARALLEL_SWEEPING_DONE - The page state when sweeping is complete or
+  // sweeping must not be performed on that page.
+  enum ParallelSweepingState {
+    PARALLEL_SWEEPING_DONE,
+    PARALLEL_SWEEPING_IN_PROGRESS,
+    PARALLEL_SWEEPING_PENDING
+  };
+
+  ParallelSweepingState parallel_sweeping() {
+    return static_cast<ParallelSweepingState>(
+        NoBarrier_Load(&parallel_sweeping_));
   }
 
-  void set_parallel_sweeping(intptr_t state) {
-    parallel_sweeping_ = state;
+  void set_parallel_sweeping(ParallelSweepingState state) {
+    NoBarrier_Store(&parallel_sweeping_, state);
   }
 
   bool TryParallelSweeping() {
-    return NoBarrier_CompareAndSwap(&parallel_sweeping_, 1, 0) == 1;
+    return NoBarrier_CompareAndSwap(&parallel_sweeping_,
+                                    PARALLEL_SWEEPING_PENDING,
+                                    PARALLEL_SWEEPING_IN_PROGRESS) ==
+                                        PARALLEL_SWEEPING_PENDING;
   }
 
   // Manage live byte count (count of bytes known to be live,
   // because they are marked black).
   void ResetLiveBytes() {
     if (FLAG_gc_verbose) {
       PrintF("ResetLiveBytes:%p:%x->0\n",
              static_cast<void*>(this), live_byte_count_);
     }
     live_byte_count_ = 0;
@@ skipping 215 matching lines @@
   SlotsBuffer* slots_buffer_;
   SkipList* skip_list_;
   intptr_t write_barrier_counter_;
   // Used by the incremental marker to keep track of the scanning progress in
   // large objects that have a progress bar and are scanned in increments.
   int progress_bar_;
   // Assuming the initial allocation on a page is sequential,
   // count highest number of bytes ever allocated on the page.
   int high_water_mark_;
 
-  intptr_t parallel_sweeping_;
+  AtomicWord parallel_sweeping_;
 
   // PagedSpace free-list statistics.
   intptr_t available_in_small_free_list_;
   intptr_t available_in_medium_free_list_;
   intptr_t available_in_large_free_list_;
   intptr_t available_in_huge_free_list_;
   intptr_t non_available_small_blocks_;
 
   static MemoryChunk* Initialize(Heap* heap,
                                  Address base,
@@ skipping 2226 matching lines @@
   }
   // Must be small, since an iteration is used for lookup.
   static const int kMaxComments = 64;
 };
 #endif
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_SPACES_H_