diff --git a/src/futex-emulation.cc b/src/futex-emulation.cc
new file mode 100644
index 0000000..991e4c3
--- /dev/null
+++ b/src/futex-emulation.cc
@@ -0,0 +1,277 @@
+// Copyright 2015 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 "src/futex-emulation.h"
+
+#include <limits>
+
+#include "src/base/macros.h"
+#include "src/base/platform/time.h"
+#include "src/conversions.h"
+#include "src/handles-inl.h"
+#include "src/isolate.h"
+#include "src/list-inl.h"
+
+namespace v8 {
+namespace internal {
+
+base::LazyMutex FutexEmulation::mutex_ = LAZY_MUTEX_INITIALIZER;
+base::LazyInstance<FutexWaitList>::type FutexEmulation::wait_list_ =
+    LAZY_INSTANCE_INITIALIZER;
+
+
+void FutexWaitListNode::NotifyWake() {
+  // Lock the FutexEmulation mutex before notifying. We know that the mutex
+  // will have been unlocked if we are currently waiting on the condition
+  // variable.
+  //
+  // The mutex may also not be locked if the other thread is currently handling
+  // interrupts, or if FutexEmulation::Wait was just called and the mutex
+  // hasn't been locked yet. In either of those cases, we set the interrupted
+  // flag to true, which will be tested after the mutex is re-locked.
+  base::LockGuard<base::Mutex> lock_guard(FutexEmulation::mutex_.Pointer());
+  if (waiting_) {
+    cond_.NotifyOne();
+    interrupted_ = true;
+  }
+}
+
+
+FutexWaitList::FutexWaitList() : head_(nullptr), tail_(nullptr) {}
+
+
+void FutexWaitList::AddNode(FutexWaitListNode* node) {
+  DCHECK(node->prev_ == nullptr && node->next_ == nullptr);
+  if (tail_) {
+    tail_->next_ = node;
+  } else {
+    head_ = node;
+  }
+
+  node->prev_ = tail_;
+  node->next_ = nullptr;
+  tail_ = node;
+}
+
+
+void FutexWaitList::RemoveNode(FutexWaitListNode* node) {
+  if (node->prev_) {
+    node->prev_->next_ = node->next_;
+  } else {
+    head_ = node->next_;
+  }
+
+  if (node->next_) {
+    node->next_->prev_ = node->prev_;
+  } else {
+    tail_ = node->prev_;
+  }
+
+  node->prev_ = node->next_ = nullptr;
+}
+
+
+Object* FutexEmulation::Wait(Isolate* isolate,
+                             Handle<JSArrayBuffer> array_buffer, size_t addr,
+                             int32_t value, double rel_timeout_ms) {
+  DCHECK(addr < NumberToSize(isolate, array_buffer->byte_length()));
+
+  void* backing_store = array_buffer->backing_store();
+  int32_t* p =
+      reinterpret_cast<int32_t*>(static_cast<int8_t*>(backing_store) + addr);
+
+  base::LockGuard<base::Mutex> lock_guard(mutex_.Pointer());
+
+  if (*p != value) {
+    return Smi::FromInt(Result::kNotEqual);
+  }
+
+  FutexWaitListNode* node = isolate->futex_wait_list_node();
+
+  node->backing_store_ = backing_store;
+  node->wait_addr_ = addr;
+  node->waiting_ = true;
+
+  bool use_timeout = rel_timeout_ms != V8_INFINITY;
+
+  base::TimeDelta rel_timeout;
+  if (use_timeout) {
+    // Convert to nanoseconds.
+    double rel_timeout_ns = rel_timeout_ms *
+                            base::Time::kNanosecondsPerMicrosecond *
+                            base::Time::kMicrosecondsPerMillisecond;
+    if (rel_timeout_ns >
+        static_cast<double>(std::numeric_limits<int64_t>::max())) {
+      // 2**63 nanoseconds is 292 years. Let's just treat anything greater as
+      // infinite.
+      use_timeout = false;
+    } else {
+      rel_timeout = base::TimeDelta::FromNanoseconds(
+          static_cast<int64_t>(rel_timeout_ns));
+    }
+  }
+
+  base::TimeTicks start_time = base::TimeTicks::Now();
+  base::TimeTicks timeout_time = start_time + rel_timeout;
+  base::TimeTicks current_time = start_time;
+
+  wait_list_.Pointer()->AddNode(node);
+
+  Object* result;
+
+  while (true) {
+    bool interrupted = node->interrupted_;
+    node->interrupted_ = false;
+
+    // Unlock the mutex here to prevent deadlock from lock ordering between
+    // mutex_ and mutexes locked by HandleInterrupts.
+    mutex_.Pointer()->Unlock();
+
+    // Because the mutex is unlocked, we have to be careful about not dropping
+    // an interrupt. The notification can happen in three different places:
+    // 1) Before Wait is called: the notification will be dropped, but
+    //    interrupted_ will be set to 1. This will be checked below.
+    // 2) After interrupted has been checked here, but before mutex_ is
+    //    acquired: interrupted is checked again below, with mutex_ locked.
+    //    Because the wakeup signal also acquires mutex_, we know it will not
+    //    be able to notify until mutex_ is released below, when waiting on the
+    //    condition variable.
+    // 3) After the mutex is released in the call to WaitFor(): this
+    // notification will wake up the condition variable. node->waiting() will
+    // be false, so we'll loop and then check interrupts.
+    if (interrupted) {
+      Object* interrupt_object = isolate->stack_guard()->HandleInterrupts();
+      if (interrupt_object->IsException()) {
+        result = interrupt_object;
+        mutex_.Pointer()->Lock();
+        break;
+      }
+    }
+
+    mutex_.Pointer()->Lock();
+
+    if (node->interrupted_) {
+      // An interrupt occured while the mutex_ was unlocked. Don't wait yet.
+      continue;
+    }
+
+    if (!node->waiting_) {
+      result = Smi::FromInt(Result::kOk);
+      break;
+    }
+
+    // No interrupts, now wait.
+    if (use_timeout) {
+      current_time = base::TimeTicks::Now();
+      if (current_time >= timeout_time) {
+        result = Smi::FromInt(Result::kTimedOut);
+        break;
+      }
+
+      base::TimeDelta time_until_timeout = timeout_time - current_time;
+      DCHECK(time_until_timeout.InMicroseconds() >= 0);
+      bool wait_for_result =
+          node->cond_.WaitFor(mutex_.Pointer(), time_until_timeout);
+      USE(wait_for_result);
+    } else {
+      node->cond_.Wait(mutex_.Pointer());
+    }
+
+    // Spurious wakeup, interrupt or timeout.
+  }
+
+  wait_list_.Pointer()->RemoveNode(node);
+  node->waiting_ = false;
+
+  return result;
+}
+
+
+Object* FutexEmulation::Wake(Isolate* isolate,
+                             Handle<JSArrayBuffer> array_buffer, size_t addr,
+                             int num_waiters_to_wake) {
+  DCHECK(addr < NumberToSize(isolate, array_buffer->byte_length()));
+
+  int waiters_woken = 0;
+  void* backing_store = array_buffer->backing_store();
+
+  base::LockGuard<base::Mutex> lock_guard(mutex_.Pointer());
+  FutexWaitListNode* node = wait_list_.Pointer()->head_;
+  while (node && num_waiters_to_wake > 0) {
+    if (backing_store == node->backing_store_ && addr == node->wait_addr_) {
+      node->waiting_ = false;
+      node->cond_.NotifyOne();
+      --num_waiters_to_wake;
+      waiters_woken++;
+    }
+
+    node = node->next_;
+  }
+
+  return Smi::FromInt(waiters_woken);
+}
+
+
+Object* FutexEmulation::WakeOrRequeue(Isolate* isolate,
+                                      Handle<JSArrayBuffer> array_buffer,
+                                      size_t addr, int num_waiters_to_wake,
+                                      int32_t value, size_t addr2) {
+  DCHECK(addr < NumberToSize(isolate, array_buffer->byte_length()));
+  DCHECK(addr2 < NumberToSize(isolate, array_buffer->byte_length()));
+
+  void* backing_store = array_buffer->backing_store();
+  int32_t* p =
+      reinterpret_cast<int32_t*>(static_cast<int8_t*>(backing_store) + addr);
+
+  base::LockGuard<base::Mutex> lock_guard(mutex_.Pointer());
+  if (*p != value) {
+    return Smi::FromInt(Result::kNotEqual);
+  }
+
+  // Wake |num_waiters_to_wake|
+  int waiters_woken = 0;
+  FutexWaitListNode* node = wait_list_.Pointer()->head_;
+  while (node) {
+    if (backing_store == node->backing_store_ && addr == node->wait_addr_) {
+      if (num_waiters_to_wake > 0) {
+        node->waiting_ = false;
+        node->cond_.NotifyOne();
+        --num_waiters_to_wake;
+        waiters_woken++;
+      } else {
+        node->wait_addr_ = addr2;
+      }
+    }
+
+    node = node->next_;
+  }
+
+  return Smi::FromInt(waiters_woken);
+}
+
+
+Object* FutexEmulation::NumWaitersForTesting(Isolate* isolate,
+                                             Handle<JSArrayBuffer> array_buffer,
+                                             size_t addr) {
+  DCHECK(addr < NumberToSize(isolate, array_buffer->byte_length()));
+  void* backing_store = array_buffer->backing_store();
+
+  base::LockGuard<base::Mutex> lock_guard(mutex_.Pointer());
+
+  int waiters = 0;
+  FutexWaitListNode* node = wait_list_.Pointer()->head_;
+  while (node) {
+    if (backing_store == node->backing_store_ && addr == node->wait_addr_ &&
+        node->waiting_) {
+      waiters++;
+    }
+
+    node = node->next_;
+  }
+
+  return Smi::FromInt(waiters);
+}
+
+}  // namespace internal
+}  // namespace v8