[heap] Adjust condition for AdjustLiveBytes to avoid concurrent access w/ sweeper

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/heap/mark-compact.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/base/sys-info.h"
 #include "src/code-stubs.h"
@@ skipping 3964 matching lines @@
     start_time = heap_->MonotonicallyIncreasingTimeInMs();
   }
 
 #ifdef DEBUG
   state_ = SWEEP_SPACES;
 #endif
 
   MoveEvacuationCandidatesToEndOfPagesList();
 
   {
+    sweeping_in_progress_ = true;

[Michael Lippautz, 2016/01/11 09:49:56]

This is not really needed as we sweep on the main thread (thus cannot have any
concurrent access with the markbits).

However, for correctness (of sweeping_in_progress()) we should indicate that we
are already sweeping?

[Hannes Payer (out of office), 2016/01/11 12:28:40]

Acknowledged.

     {
       GCTracer::Scope sweep_scope(heap()->tracer(),
                                   GCTracer::Scope::MC_SWEEP_OLD);
       StartSweepSpace(heap()->old_space());
     }
     {
       GCTracer::Scope sweep_scope(heap()->tracer(),
                                   GCTracer::Scope::MC_SWEEP_CODE);
       StartSweepSpace(heap()->code_space());
     }
     {
       GCTracer::Scope sweep_scope(heap()->tracer(),
                                   GCTracer::Scope::MC_SWEEP_MAP);
       StartSweepSpace(heap()->map_space());
     }
-    sweeping_in_progress_ = true;
     if (FLAG_concurrent_sweeping) {
       StartSweeperThreads();
     }
   }
 
   // Deallocate unmarked large objects.
   heap_->lo_space()->FreeUnmarkedObjects();
 
   // Give pages that are queued to be freed back to the OS. Invalid store
   // buffer entries are already filter out. We can just release the memory.
@@ skipping 94 matching lines @@
     MarkBit mark_bit = Marking::MarkBitFrom(host);
     if (Marking::IsBlack(mark_bit)) {
       RelocInfo rinfo(isolate(), pc, RelocInfo::CODE_TARGET, 0, host);
       RecordRelocSlot(&rinfo, target);
     }
   }
 }
 
 }  // namespace internal
 }  // namespace v8