Fix for 3303 MultithreadedParallelIsolates has a race condition.

src/arm/codegen-arm.cc

Index: src/arm/codegen-arm.cc
diff --git a/src/arm/codegen-arm.cc b/src/arm/codegen-arm.cc
index a8e38777bf5a79e44ff7be34e2d328d94d7095f3..8a46006eb9b773d253c34710a690bee952489d15 100644
--- a/src/arm/codegen-arm.cc
+++ b/src/arm/codegen-arm.cc
@@ -822,47 +822,46 @@ void MathExpGenerator::EmitMathExp(MacroAssembler* masm,
 static const uint32_t kCodeAgePatchFirstInstruction = 0xe24f0008;
 #endif
 
-static byte* GetNoCodeAgeSequence(uint32_t* length) {
-  // The sequence of instructions that is patched out for aging code is the
-  // following boilerplate stack-building prologue that is found in FUNCTIONS
-  static bool initialized = false;
-  static uint32_t sequence[kNoCodeAgeSequenceLength];
-  byte* byte_sequence = reinterpret_cast<byte*>(sequence);
-  *length = kNoCodeAgeSequenceLength * Assembler::kInstrSize;
-  if (!initialized) {
-    // Since patcher is a large object, allocate it dynamically when needed,
-    // to avoid overloading the stack in stress conditions.
-    SmartPointer<CodePatcher>
-        patcher(new CodePatcher(byte_sequence, kNoCodeAgeSequenceLength));
-    PredictableCodeSizeScope scope(patcher->masm(), *length);
-    patcher->masm()->PushFixedFrame(r1);
-    patcher->masm()->nop(ip.code());
-    patcher->masm()->add(
-        fp, sp, Operand(StandardFrameConstants::kFixedFrameSizeFromFp));
-    initialized = true;
-  }
-  return byte_sequence;
+CodeAgingHelper::CodeAgingHelper() {
+  ASSERT(young_sequence_.length() == kNoCodeAgeSequenceLength);
+  // Since patcher is a large object, allocate it dynamically when needed,
+  // to avoid overloading the stack in stress conditions.
+  // DONT_FLUSH is used because the CodeAgingHelper is initialized early in
+  // the process, before ARM simulator ICache is setup.
+  SmartPointer<CodePatcher> patcher(
+      new CodePatcher(young_sequence_.start(),
+                      young_sequence_.length() / Assembler::kInstrSize,
+                      CodePatcher::DONT_FLUSH));
+  PredictableCodeSizeScope scope(patcher->masm(), young_sequence_.length());
+  patcher->masm()->PushFixedFrame(r1);
+  patcher->masm()->nop(ip.code());
+  patcher->masm()->add(
+      fp, sp, Operand(StandardFrameConstants::kFixedFrameSizeFromFp));
+}
+
+
+#ifdef DEBUG
+bool CodeAgingHelper::IsOld(byte* candidate) const {
+  return Memory::uint32_at(candidate) == kCodeAgePatchFirstInstruction;
 }
+#endif
 
 
-bool Code::IsYoungSequence(byte* sequence) {
-  uint32_t young_length;
-  byte* young_sequence = GetNoCodeAgeSequence(&young_length);
-  bool result = !memcmp(sequence, young_sequence, young_length);
-  ASSERT(result ||
-         Memory::uint32_at(sequence) == kCodeAgePatchFirstInstruction);
+bool Code::IsYoungSequence(Isolate* isolate, byte* sequence) {
+  bool result = isolate->code_aging_helper()->IsYoung(sequence);
+  ASSERT(result || isolate->code_aging_helper()->IsOld(sequence));
   return result;
 }
 
 
-void Code::GetCodeAgeAndParity(byte* sequence, Age* age,
+void Code::GetCodeAgeAndParity(Isolate* isolate, byte* sequence, Age* age,
                                MarkingParity* parity) {
-  if (IsYoungSequence(sequence)) {
+  if (IsYoungSequence(isolate, sequence)) {
     *age = kNoAgeCodeAge;
     *parity = NO_MARKING_PARITY;
   } else {
     Address target_address = Memory::Address_at(
-        sequence + Assembler::kInstrSize * (kNoCodeAgeSequenceLength - 1));
+        sequence + (kNoCodeAgeSequenceLength - Assembler::kInstrSize));
     Code* stub = GetCodeFromTargetAddress(target_address);
     GetCodeAgeAndParity(stub, age, parity);
   }
@@ -873,10 +872,9 @@ void Code::PatchPlatformCodeAge(Isolate* isolate,
                                 byte* sequence,
                                 Code::Age age,
                                 MarkingParity parity) {
-  uint32_t young_length;
-  byte* young_sequence = GetNoCodeAgeSequence(&young_length);
+  uint32_t young_length = isolate->code_aging_helper()->young_sequence_length();
   if (age == kNoAgeCodeAge) {
-    CopyBytes(sequence, young_sequence, young_length);
+    isolate->code_aging_helper()->CopyYoungSequenceTo(sequence);
     CPU::FlushICache(sequence, young_length);
   } else {
     Code* stub = GetCodeAgeStub(isolate, age, parity);