[heap] Move start of incremental marking in allocation

Move start of incremental marking out of
RefillLinearAllocationAreaFromFreeList. This avoids a potential
safepoint while holding allocation_mutex_.

Bug: v8:10315
Change-Id: Ieb60ac68f26199eea7b6b7ad6d874851382f3d69
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2287496
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68751}

src/heap/paged-spaces.cc

@@ -529,12 +529,6 @@ bool PagedSpace::RefillLinearAllocationAreaFromFreeList(
   // if it is big enough.
   FreeLinearAllocationArea();
 
-  if (!is_local_space()) {
-    heap()->StartIncrementalMarkingIfAllocationLimitIsReached(
-        heap()->GCFlagsForIncrementalMarking(),
-        kGCCallbackScheduleIdleGarbageCollection);
-  }
-
   size_t new_node_size = 0;
   FreeSpace new_node =
       free_list_->Allocate(size_in_bytes, &new_node_size, origin);
@@ -1019,6 +1013,15 @@ AllocationResult PagedSpace::AllocateRawSlow(int size_in_bytes,
       top_on_previous_step_ ? top() - top_on_previous_step_ : 0;
   DCHECK_IMPLIES(!SupportsInlineAllocation(), bytes_since_last == 0);
 
+  if (!is_local_space()) {
+    // Start incremental marking before the actual allocation, this allows the
+    // allocation function to mark the object black when incremental marking is
+    // running.
+    heap()->StartIncrementalMarkingIfAllocationLimitIsReached(
+        heap()->GCFlagsForIncrementalMarking(),
+        kGCCallbackScheduleIdleGarbageCollection);
+  }
+
 #ifdef V8_HOST_ARCH_32_BIT
   AllocationResult result =
       alignment != kWordAligned

test/cctest/heap/test-external-string-tracker.cc

@@ -130,6 +130,7 @@ TEST(ExternalString_ExternalBackingStoreSizeIncreasesMarkCompact) {
 }
 
 TEST(ExternalString_ExternalBackingStoreSizeIncreasesAfterExternalization) {
+  ManualGCScope manual_gc_scope;
   CcTest::InitializeVM();
   LocalContext env;
   v8::Isolate* isolate = env->GetIsolate();