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

runtime/vm/flow_graph_inliner.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_inliner.h"
 
 #include "vm/aot_optimizer.h"
 #include "vm/block_scheduler.h"
 #include "vm/branch_optimizer.h"
 #include "vm/compiler.h"
@@ skipping 676 matching lines @@
     }
 
     // Save and clear deopt id.
     const intptr_t prev_deopt_id = thread()->deopt_id();
     thread()->set_deopt_id(0);
     Error& error = Error::Handle();
     {
       // 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*>();
         const bool clone_ic_data = Compiler::IsBackgroundCompilation();
         function.RestoreICDataMap(ic_data_array, clone_ic_data);
         if (Compiler::IsBackgroundCompilation() &&
             (function.ic_data_array() == Array::null())) {
           Compiler::AbortBackgroundCompilation(Thread::kNoDeoptId);
         }
 
@@ skipping 2358 matching lines @@
       return InlineDoubleOp(flow_graph, Token::kMUL, call, entry, last);
     case MethodRecognizer::kDoubleDiv:
       return InlineDoubleOp(flow_graph, Token::kDIV, call, entry, last);
     default:
       return false;
   }
 }
 
 
 }  // namespace dart