Fix for 3303 MultithreadedParallelIsolates has a race condition.

src/arm/simulator-arm.cc

Index: src/arm/simulator-arm.cc
diff --git a/src/arm/simulator-arm.cc b/src/arm/simulator-arm.cc
index 80b46e04df366b39cb40724613344beaf4882304..6197de232d200d3e88cc05802d864e8a626c8193 100644
--- a/src/arm/simulator-arm.cc
+++ b/src/arm/simulator-arm.cc
@@ -634,6 +634,7 @@ void Simulator::set_last_debugger_input(char* input) {
 void Simulator::FlushICache(v8::internal::HashMap* i_cache,
                             void* start_addr,
                             size_t size) {
+  if (i_cache == NULL) return;

[mvstanton, 2014/05/06 09:55:46]

The reason this condition was being hit at snapshot time, is that now we create
instructions on isolate initialization, rather than lazily when we want to test
code for young/old status. In the ARM simulator environment, caching isn't set
up until later in the initialization process.

A better fix is that when the CodePatcher is initialized to create the
CodeAgingHelper::young_sequence_, we can ask that code flushing not be used.

   intptr_t start = reinterpret_cast<intptr_t>(start_addr);
   int intra_line = (start & CachePage::kLineMask);
   start -= intra_line;