Fix for 3303 MultithreadedParallelIsolates has a race condition.

src/arm/simulator-arm.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdarg.h>
 #include <stdlib.h>
 #include <cmath>
 
 #include "v8.h"
 
@@ skipping 616 matching lines @@
 
 void Simulator::set_last_debugger_input(char* input) {
   DeleteArray(last_debugger_input_);
   last_debugger_input_ = 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;
   size += intra_line;
   size = ((size - 1) | CachePage::kLineMask) + 1;
   int offset = (start & CachePage::kPageMask);
   while (!AllOnOnePage(start, size - 1)) {
     int bytes_to_flush = CachePage::kPageSize - offset;
     FlushOnePage(i_cache, start, bytes_to_flush);
     start += bytes_to_flush;
@@ skipping 3182 matching lines @@
   uintptr_t address = *stack_slot;
   set_register(sp, current_sp + sizeof(uintptr_t));
   return address;
 }
 
 } }  // namespace v8::internal
 
 #endif  // USE_SIMULATOR
 
 #endif  // V8_TARGET_ARCH_ARM