diff -r 000000000000 -r 6474c204b198 js/jsd/jsd_lock.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/js/jsd/jsd_lock.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,228 @@
+/* -*- 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/. */
+
+/*
+ * JavaScript Debugging support - Locking and threading support
+ */
+
+/*                                                                           
+* ifdef JSD_USE_NSPR_LOCKS then you must build and run against NSPR2.       
+* Otherwise, there are stubs that can be filled in with your own locking     
+* code. Also, note that these stubs include a jsd_CurrentThread()            
+* implementation that only works on Win32 - this is needed for the inprocess 
+* Java-based debugger.                                                       
+*/                                                                           
+
+#include "jsd.h"
+
+#include "js/Utility.h"
+
+#ifdef JSD_THREADSAFE
+
+#ifdef JSD_USE_NSPR_LOCKS
+
+#include "prlock.h"
+#include "prthread.h"
+
+#ifdef JSD_ATTACH_THREAD_HACK
+#include "pprthred.h"   /* need this as long as JS_AttachThread is needed */
+#endif
+
+struct JSDStaticLock
+{
+    void*     owner;
+    PRLock*   lock;
+    int       count;
+#ifdef DEBUG
+    uint16_t  sig;
+#endif
+};
+
+/* 
+ * This exists to wrap non-NSPR theads (e.g. Java threads) in NSPR wrappers.
+ * XXX We ignore the memory leak issue.
+ * It is claimed that future versions of NSPR will automatically wrap on 
+ * the call to PR_GetCurrentThread.
+ *
+ * XXX We ignore the memory leak issue - i.e. we never call PR_DetachThread.
+ *
+ */
+#undef _CURRENT_THREAD
+#ifdef JSD_ATTACH_THREAD_HACK
+#define _CURRENT_THREAD(out)                                                  \
+JS_BEGIN_MACRO                                                                \
+    out = (void*) PR_GetCurrentThread();                                      \
+    if(!out)                                                                  \
+        out = (void*) JS_AttachThread(PR_USER_THREAD, PR_PRIORITY_NORMAL,     \
+                                      nullptr);                               \
+    MOZ_ASSERT(out);                                                          \
+JS_END_MACRO
+#else
+#define _CURRENT_THREAD(out)             \
+JS_BEGIN_MACRO                           \
+    out = (void*) PR_GetCurrentThread(); \
+    MOZ_ASSERT(out);                     \
+JS_END_MACRO
+#endif
+
+#ifdef DEBUG
+#define JSD_LOCK_SIG 0x10CC10CC
+void ASSERT_VALID_LOCK(JSDStaticLock* lock)
+{
+    MOZ_ASSERT(lock);
+    MOZ_ASSERT(lock->lock);
+    MOZ_ASSERT(lock->count >= 0);
+    MOZ_ASSERT(lock->sig == (uint16_t) JSD_LOCK_SIG);
+}    
+#else
+#define ASSERT_VALID_LOCK(x) ((void)0)
+#endif
+
+JSDStaticLock*
+jsd_CreateLock()
+{
+    JSDStaticLock* lock;
+
+    if( ! (lock = js_pod_calloc<JSDStaticLock>()) ||
+        ! (lock->lock = PR_NewLock()) )
+    {
+        if(lock)
+        {
+            free(lock);
+            lock = nullptr;
+        }
+    }
+#ifdef DEBUG
+    if(lock) lock->sig = (uint16_t) JSD_LOCK_SIG;
+#endif
+    return lock;
+}    
+
+void
+jsd_Lock(JSDStaticLock* lock)
+{
+    void* me;
+    ASSERT_VALID_LOCK(lock);
+    _CURRENT_THREAD(me);
+
+    if(lock->owner == me)
+    {
+        lock->count++;
+        MOZ_ASSERT(lock->count > 1);
+    }
+    else
+    {
+        PR_Lock(lock->lock);            /* this can block... */
+        MOZ_ASSERT(lock->owner == 0);
+        MOZ_ASSERT(lock->count == 0);
+        lock->count = 1;
+        lock->owner = me;
+    }
+}    
+
+void
+jsd_Unlock(JSDStaticLock* lock)
+{
+    void* me;
+    ASSERT_VALID_LOCK(lock);
+    _CURRENT_THREAD(me);
+
+    /* it's an error to unlock a lock you don't own */
+    MOZ_ASSERT(lock->owner == me);
+    if(lock->owner != me)
+        return;
+
+    if(--lock->count == 0)
+    {
+        lock->owner = nullptr;
+        PR_Unlock(lock->lock);
+    }
+}    
+
+#ifdef DEBUG
+bool
+jsd_IsLocked(JSDStaticLock* lock)
+{
+    void* me;
+    ASSERT_VALID_LOCK(lock);
+    _CURRENT_THREAD(me);
+    if (lock->owner != me)
+        return false;
+    MOZ_ASSERT(lock->count > 0);
+    return true;
+}    
+#endif /* DEBUG */
+
+void*
+jsd_CurrentThread()
+{
+    void* me;
+    _CURRENT_THREAD(me);
+    return me;
+}    
+
+
+#else  /* ! JSD_USE_NSPR_LOCKS */
+
+#ifdef WIN32    
+#pragma message("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")
+#pragma message("!! you are compiling the stubbed version of jsd_lock.c !!")
+#pragma message("!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!")
+#endif
+
+/*
+ * NOTE: 'Real' versions of these locks must be reentrant in the sense that 
+ * they support nested calls to lock and unlock. 
+ */
+
+void*
+jsd_CreateLock()
+{
+    return (void*)1;
+}    
+
+void
+jsd_Lock(void* lock)
+{
+}    
+
+void
+jsd_Unlock(void* lock)
+{
+}    
+
+#ifdef DEBUG
+bool
+jsd_IsLocked(void* lock)
+{
+    return true;
+}    
+#endif /* DEBUG */
+
+/* 
+ * This Windows only thread id code is here to allow the Java-based 
+ * JSDebugger to work with the single threaded js.c shell (even without 
+ * real locking and threading support).
+ */
+
+#ifdef WIN32    
+/* bogus (but good enough) declaration*/
+extern void* __stdcall GetCurrentThreadId(void);
+#endif
+
+void*
+jsd_CurrentThread()
+{
+#ifdef WIN32    
+    return GetCurrentThreadId();
+#else
+    return (void*)1;
+#endif
+}    
+
+#endif /* JSD_USE_NSPR_LOCKS */
+
+#endif /* JSD_THREADSAFE */