Track loading happening in parallel with background compilation and abort compilation if necessary.

runtime/vm/flow_graph_inliner.cc

Index: runtime/vm/flow_graph_inliner.cc
diff --git a/runtime/vm/flow_graph_inliner.cc b/runtime/vm/flow_graph_inliner.cc
index 437c684f6e4ba91b2ccb91e38598b0923c66ad56..7283257c6f275585ad2d92035cfa86050d6629b6 100644
--- a/runtime/vm/flow_graph_inliner.cc
+++ b/runtime/vm/flow_graph_inliner.cc
@@ -694,14 +694,28 @@ class CallSiteInliner : public ValueObject {
       // Install bailout jump.
       LongJumpScope jump;
       if (setjmp(*jump.Set()) == 0) {
+        Isolate* isolate = Isolate::Current();
+        // Makes sure no classes are loaded during parsing in background.
+        const uint32_t loading_invalidation_gen_at_start =
+            isolate->loading_invalidation_gen();
         // Parse the callee function.
         bool in_cache;
         ParsedFunction* parsed_function;
-        {
+       {
           CSTAT_TIMER_SCOPE(thread(), graphinliner_parse_timer);
           parsed_function = GetParsedFunction(function, &in_cache);
         }
 
+        if (Compiler::IsBackgroundCompilation()) {
+          if (isolate->top_level_parsing() ||

[siva, 2016/03/28 17:20:14]

This value is set in the mutator thread and accessed here in the background
compiler thread, seems racy.

Do you need this value, isn't tracking loading_invalidation_gen_ sufficient as
you seem to increment that too when top level parsing is done.

[srdjan, 2016/03/28 19:54:54]

dito

+                  (loading_invalidation_gen_at_start !=
+                   isolate->loading_invalidation_gen())) {
+            // Loading occured while parsing. We need to abort here because
+            // state changed while compiling.
+            Compiler::AbortBackgroundCompilation(Thread::kNoDeoptId);
+          }
+        }
+
         // Load IC data for the callee.
         ZoneGrowableArray<const ICData*>* ic_data_array =
               new(Z) ZoneGrowableArray<const ICData*>();