Fix race in root marking.

There was a race which caused the class linker / intern table to not
become dirty after adding a root. We now guard the is dirty flag by
the corresponding locks to prevent this from occuring. This was
causing roots to be occasionally missed.

Also fixes the bug where we occasionally scan more cards than
needed.

Bug: 10626133

Change-Id: I0f6e72d92035ff463954d66988ef610ea0df61be

1 files changed, 9 insertions, 7 deletions

diff --git a/runtime/intern_table.cc b/runtime/intern_table.cc
index e3a75cf..89c15f8 100644
--- a/runtime/intern_table.cc
+++ b/runtime/intern_table.cc
@@ -42,13 +42,15 @@ void InternTable::DumpForSigQuit(std::ostream& os) const {
 }
 
 void InternTable::VisitRoots(RootVisitor* visitor, void* arg,
-                             bool clean_dirty) {
+                             bool only_dirty, bool clean_dirty) {
   MutexLock mu(Thread::Current(), intern_table_lock_);
-  for (const auto& strong_intern : strong_interns_) {
-    visitor(strong_intern.second, arg);
-  }
-  if (clean_dirty) {
-    is_dirty_ = false;
+  if (!only_dirty || is_dirty_) {
+    for (const auto& strong_intern : strong_interns_) {
+      visitor(strong_intern.second, arg);
+    }
+    if (clean_dirty) {
+      is_dirty_ = false;
+    }
   }
   // Note: we deliberately don't visit the weak_interns_ table and the immutable
   // image roots.
@@ -123,7 +125,7 @@ mirror::String* InternTable::Insert(mirror::String* s, bool is_strong) {
     }
 
     // Mark as dirty so that we rescan the roots.
-    Dirty();
+    is_dirty_ = true;
 
     // Check the image for a match.
     mirror::String* image = LookupStringFromImage(s);