diff -r 000000000000 -r 6474c204b198 js/src/vm/Monitor.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/src/vm/Monitor.h	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,162 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef vm_Monitor_h
+#define vm_Monitor_h
+
+#ifdef JS_THREADSAFE
+#include "mozilla/DebugOnly.h"
+#endif
+
+#include <stddef.h>
+
+#include "jslock.h"
+
+#include "js/Utility.h"
+
+namespace js {
+
+// A base class used for types intended to be used in a parallel
+// fashion, such as the workers in the |ThreadPool| class.  Combines a
+// lock and a condition variable.  You can acquire the lock or signal
+// the condition variable using the |AutoLockMonitor| type.
+
+class Monitor
+{
+  protected:
+    friend class AutoLockMonitor;
+    friend class AutoUnlockMonitor;
+
+    PRLock *lock_;
+    PRCondVar *condVar_;
+
+  public:
+    Monitor()
+      : lock_(nullptr),
+        condVar_(nullptr)
+    { }
+
+    ~Monitor() {
+#ifdef JS_THREADSAFE
+        if (lock_)
+            PR_DestroyLock(lock_);
+        if (condVar_)
+            PR_DestroyCondVar(condVar_);
+#endif
+    }
+
+    bool init();
+};
+
+class AutoLockMonitor
+{
+  private:
+#ifdef JS_THREADSAFE
+    Monitor &monitor;
+#endif
+
+  public:
+    AutoLockMonitor(Monitor &monitor)
+#ifdef JS_THREADSAFE
+      : monitor(monitor)
+    {
+        PR_Lock(monitor.lock_);
+    }
+#else
+    {}
+#endif
+
+    ~AutoLockMonitor() {
+#ifdef JS_THREADSAFE
+        PR_Unlock(monitor.lock_);
+#endif
+    }
+
+    bool isFor(Monitor &other) const {
+#ifdef JS_THREADSAFE
+        return monitor.lock_ == other.lock_;
+#else
+        return true;
+#endif
+    }
+
+    void wait(PRCondVar *condVar) {
+#ifdef JS_THREADSAFE
+        mozilla::DebugOnly<PRStatus> status =
+          PR_WaitCondVar(condVar, PR_INTERVAL_NO_TIMEOUT);
+        MOZ_ASSERT(status == PR_SUCCESS);
+#endif
+    }
+
+    void wait() {
+#ifdef JS_THREADSAFE
+        wait(monitor.condVar_);
+#endif
+    }
+
+    void notify(PRCondVar *condVar) {
+#ifdef JS_THREADSAFE
+        mozilla::DebugOnly<PRStatus> status = PR_NotifyCondVar(condVar);
+        MOZ_ASSERT(status == PR_SUCCESS);
+#endif
+    }
+
+    void notify() {
+#ifdef JS_THREADSAFE
+        notify(monitor.condVar_);
+#endif
+    }
+
+    void notifyAll(PRCondVar *condVar) {
+#ifdef JS_THREADSAFE
+        mozilla::DebugOnly<PRStatus> status = PR_NotifyAllCondVar(monitor.condVar_);
+        MOZ_ASSERT(status == PR_SUCCESS);
+#endif
+    }
+
+    void notifyAll() {
+#ifdef JS_THREADSAFE
+        notifyAll(monitor.condVar_);
+#endif
+    }
+};
+
+class AutoUnlockMonitor
+{
+  private:
+#ifdef JS_THREADSAFE
+    Monitor &monitor;
+#endif
+
+  public:
+    AutoUnlockMonitor(Monitor &monitor)
+#ifdef JS_THREADSAFE
+      : monitor(monitor)
+    {
+        PR_Unlock(monitor.lock_);
+    }
+#else
+    {}
+#endif
+
+    ~AutoUnlockMonitor() {
+#ifdef JS_THREADSAFE
+        PR_Lock(monitor.lock_);
+#endif
+    }
+
+    bool isFor(Monitor &other) const {
+#ifdef JS_THREADSAFE
+        return monitor.lock_ == other.lock_;
+#else
+        return true;
+#endif
+    }
+};
+
+} // namespace js
+
+#endif /* vm_Monitor_h */