Safepointing in GC

runtime/vm/pages.cc

Index: runtime/vm/pages.cc
diff --git a/runtime/vm/pages.cc b/runtime/vm/pages.cc
index f45c5b04a95f5715b7f77d3ab3e2ccd2571e8ffe..dd3b82845499cc6063aadf5d9b9a473cfae8a18f 100644
--- a/runtime/vm/pages.cc
+++ b/runtime/vm/pages.cc
@@ -11,6 +11,7 @@
 #include "vm/lockers.h"
 #include "vm/object.h"
 #include "vm/os_thread.h"
+#include "vm/thread_registry.h"
 #include "vm/verified_memory.h"
 #include "vm/virtual_memory.h"
 
@@ -768,6 +769,8 @@ void PageSpace::MarkSweep(bool invoke_api_callbacks) {
     set_tasks(1);
   }
 
+  int safepoint_id = isolate->thread_registry()->SafepointThreads();
+
   // Perform various cleanup that relies on no tasks interfering.
   isolate->class_table()->FreeOldTables();
 
@@ -880,8 +883,8 @@ void PageSpace::MarkSweep(bool invoke_api_callbacks) {
       }
     } else {
       // Start the concurrent sweeper task now.
-      GCSweeper::SweepConcurrent(
-          isolate, pages_, pages_tail_, &freelist_[HeapPage::kData]);
+      GCSweeper::SweepConcurrent(isolate, pages_, pages_tail_,
+                                 &freelist_[HeapPage::kData], safepoint_id);
     }
   }
 
@@ -907,6 +910,8 @@ void PageSpace::MarkSweep(bool invoke_api_callbacks) {
     freelist_[HeapPage::kExecutable].Print();
   }
 
+  isolate->thread_registry()->ResumeAllThreads();  // Rename
+
   // Done, reset the task count.
   {
     MonitorLocker ml(tasks_lock());