Wait for sweeper threads when a scan on scavenge page is not swept.

src/mark-compact.cc

Index: src/mark-compact.cc
diff --git a/src/mark-compact.cc b/src/mark-compact.cc
index 595d6ee3ce09ddf35ae26cd6a7f7444e78c48802..81361f02aae4023a3aa5d7b202ed89fd73828e7f 100644
--- a/src/mark-compact.cc
+++ b/src/mark-compact.cc
@@ -4098,39 +4098,44 @@ int MarkCompactCollector::SweepConservatively(PagedSpace* space,
 
 int MarkCompactCollector::SweepInParallel(PagedSpace* space,
                                           int required_freed_bytes) {
-  PageIterator it(space);
-  FreeList* free_list = space == heap()->old_pointer_space()
-                            ? free_list_old_pointer_space_.get()
-                            : free_list_old_data_space_.get();
-  FreeList private_free_list(space);
   int max_freed = 0;
   int max_freed_overall = 0;
+  PageIterator it(space);
   while (it.has_next()) {
     Page* p = it.next();
-    if (p->TryParallelSweeping()) {
-      if (space->swept_precisely()) {
-        max_freed = SweepPrecisely<SWEEP_ONLY,
-                                   SWEEP_IN_PARALLEL,
-                                   IGNORE_SKIP_LIST,
-                                   IGNORE_FREE_SPACE>(
-                                       space, &private_free_list, p, NULL);
-      } else {
-        max_freed = SweepConservatively<SWEEP_IN_PARALLEL>(
-            space, &private_free_list, p);
-      }
-      ASSERT(max_freed >= 0);
-      free_list->Concatenate(&private_free_list);
-      if (required_freed_bytes > 0 && max_freed >= required_freed_bytes) {
-        return max_freed;
-      }
-      max_freed_overall = Max(max_freed, max_freed_overall);
+    max_freed = SweepInParallel(p, space);
+    ASSERT(max_freed >= 0);
+    if (required_freed_bytes > 0 && max_freed >= required_freed_bytes) {
+      return max_freed;
     }
+    max_freed_overall = Max(max_freed, max_freed_overall);
     if (p == space->end_of_unswept_pages()) break;
   }
   return max_freed_overall;
 }
 
 
+int MarkCompactCollector::SweepInParallel(Page* page, PagedSpace* space) {
+  int max_freed = 0;
+  if (page->TryParallelSweeping()) {
+    FreeList* free_list = space == heap()->old_pointer_space()
+                              ? free_list_old_pointer_space_.get()
+                              : free_list_old_data_space_.get();
+    FreeList private_free_list(space);
+    if (space->swept_precisely()) {
+      max_freed = SweepPrecisely<SWEEP_ONLY, SWEEP_IN_PARALLEL,
+                                 IGNORE_SKIP_LIST, IGNORE_FREE_SPACE>(
+          space, &private_free_list, page, NULL);
+    } else {
+      max_freed = SweepConservatively<SWEEP_IN_PARALLEL>(
+          space, &private_free_list, page);
+    }
+    free_list->Concatenate(&private_free_list);
+  }
+  return max_freed;
+}
+
+
 void MarkCompactCollector::SweepSpace(PagedSpace* space, SweeperType sweeper) {
   space->set_swept_precisely(sweeper == PRECISE ||
                              sweeper == CONCURRENT_PRECISE ||