Fix race condition in Redirection global list using CAS.

runtime/vm/simulator_arm64.cc

 // Copyright (c) 2014, 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 <setjmp.h>  // NOLINT
 #include <stdlib.h>
 
 #include "vm/globals.h"
 #if defined(TARGET_ARCH_ARM64)
 
@@ skipping 832 matching lines @@
  private:
   static const int32_t kRedirectInstruction = Instr::kRedirectInstruction;
   Redirection(uword external_function,
               Simulator::CallKind call_kind,
               int argument_count)
       : external_function_(external_function),
         call_kind_(call_kind),
         argument_count_(argument_count),
         hlt_instruction_(kRedirectInstruction),
         next_(list_) {
-    list_ = this;
+    // Atomically prepend this element to the front of the global list.
+    // Note: Since elements are never removed, there is no ABA issue.
+    Redirection* old_list = list_;
+    do {
+      next_ = old_list;
+      old_list = reinterpret_cast<Redirection*>(
+          AtomicOperations::CompareAndSwapWord(
+              reinterpret_cast<uword*>(&list_),
+              reinterpret_cast<uword>(next_),
+              reinterpret_cast<uword>(this)));
+    } while (old_list != next_);
   }
 
   uword external_function_;
   Simulator::CallKind call_kind_;
   int argument_count_;
   uint32_t hlt_instruction_;
   Redirection* next_;
   static Redirection* list_;
 };
 
@@ skipping 2631 matching lines @@
   set_register(NULL, kExceptionObjectReg, bit_cast<int64_t>(raw_exception));
   set_register(NULL, kStackTraceObjectReg, bit_cast<int64_t>(raw_stacktrace));
   buf->Longjmp();
 }
 
 }  // namespace dart
 
 #endif  // !defined(HOST_ARCH_ARM64)
 
 #endif  // defined TARGET_ARCH_ARM64