Safepointing in GC

runtime/vm/thread_registry.cc

Index: runtime/vm/thread_registry.cc
diff --git a/runtime/vm/thread_registry.cc b/runtime/vm/thread_registry.cc
index 8ade009c6035e6762ee9f45b39b1ce2dcc00100c..000175fb2c824033cc62a117079b60a47a430d8d 100644
--- a/runtime/vm/thread_registry.cc
+++ b/runtime/vm/thread_registry.cc
@@ -9,7 +9,7 @@
 
 namespace dart {
 
-void ThreadRegistry::SafepointThreads() {
+SafepointId ThreadRegistry::SafepointThreads() {
   MonitorLocker ml(monitor_);
   // First wait for any older rounds that are still in progress.
   while (in_rendezvous_) {
@@ -20,7 +20,16 @@ void ThreadRegistry::SafepointThreads() {
   // Start a new round.
   in_rendezvous_ = true;
   ++round_;  // Overflows after 240+ years @ 10^9 safepoints per second.
-  remaining_ = CountScheduledLocked();
+  // Count the number of threads that should participate in this round.
+  remaining_ = 0;
+  for (int i = 0; i < entries_.length(); ++i) {
+    const Entry& entry = entries_[i];
+    if (entry.scheduled) {
+      // All threads that are running should participate.
+      ASSERT(IsParticipant(entry.thread));
+      ++remaining_;
+    }
+  }
   Isolate* isolate = Isolate::Current();
   // We only expect this method to be called from within the isolate itself.
   ASSERT(isolate->thread_registry() == this);
@@ -33,6 +42,7 @@ void ThreadRegistry::SafepointThreads() {
   while (remaining_ > 0) {
     ml.Wait(Monitor::kNoTimeout);
   }
+  return round_;
 }
 
 
@@ -69,16 +79,4 @@ void ThreadRegistry::CheckSafepointLocked() {
   }
 }
 
-
-intptr_t ThreadRegistry::CountScheduledLocked() {
-  intptr_t count = 0;
-  for (int i = 0; i < entries_.length(); ++i) {
-    const Entry& entry = entries_[i];
-    if (entry.scheduled) {
-      ++count;
-    }
-  }
-  return count;
-}
-
 }  // namespace dart