Make sure that we push a null JSContext on the current thread's XPConnect stack

before processing events.  Bug 326777, r=bsmedberg, sr=jst

js/src/xpconnect/src/nsXPConnect.cpp

@@ -50,8 +50,12 @@
 #include "jsfun.h"
 #include "jsobj.h"
 #include "jsscript.h"
+#include "nsThreadUtilsInternal.h"
 
-NS_IMPL_THREADSAFE_ISUPPORTS2(nsXPConnect,nsIXPConnect,nsISupportsWeakReference)
+NS_IMPL_THREADSAFE_ISUPPORTS3(nsXPConnect,
+                              nsIXPConnect,
+                              nsISupportsWeakReference,
+                              nsIThreadObserver)
 
 nsXPConnect* nsXPConnect::gSelf = nsnull;
 JSBool       nsXPConnect::gOnceAliveNowDead = JS_FALSE;
@@ -286,6 +290,10 @@ nsXPConnect::GetXPConnect()
             // Initial extra ref to keep the singleton alive
             // balanced by explicit call to ReleaseXPConnectSingleton()
             NS_ADDREF(gSelf);
+            if (NS_FAILED(NS_SetGlobalThreadObserver(gSelf))) {
+                NS_RELEASE(gSelf);
+                // Fall through to returning null
+            }
         }
     }
     return gSelf;
@@ -307,6 +315,7 @@ nsXPConnect::ReleaseXPConnectSingleton()
     nsXPConnect* xpc = gSelf;
     if(xpc)
     {
+        NS_SetGlobalThreadObserver(nsnull);
 
 #ifdef XPC_TOOLS_SUPPORT
         if(xpc->mProfiler)
@@ -2014,6 +2023,31 @@ nsXPConnect::FlagSystemFilenamePrefix(const char *aFilenamePrefix)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsXPConnect::OnProcessNextEvent(nsIThreadInternal *aThread, PRBool aMayWait,
+                                PRUint32 aRecursionDepth)
+{
+    // Push a null JSContext so that we don't see any script during
+    // event processing.
+    NS_ENSURE_STATE(mContextStack);
+    return mContextStack->Push(nsnull);
+}
+
+NS_IMETHODIMP
+nsXPConnect::AfterProcessNextEvent(nsIThreadInternal *aThread,
+                                   PRUint32 aRecursionDepth)
+{
+    NS_ENSURE_STATE(mContextStack);
+    return mContextStack->Pop(nsnull);
+}
+
+NS_IMETHODIMP
+nsXPConnect::OnDispatchedEvent(nsIThreadInternal* aThread)
+{
+    NS_NOTREACHED("Why tell us?");
+    return NS_ERROR_UNEXPECTED;
+}
+
 #ifdef DEBUG
 /* These are here to be callable from a debugger */
 JS_BEGIN_EXTERN_C

js/src/xpconnect/src/xpcprivate.h

@@ -126,6 +126,8 @@
 #include "nsIXPCToolsProfiler.h"
 #endif
 
+#include "nsIThreadInternal.h"
+
 #ifdef XPC_IDISPATCH_SUPPORT
 // This goop was added because of EXCEPINFO in ThrowCOMError
 // This include is here, because it needs to occur before the undefines below
@@ -426,6 +428,7 @@ const PRBool OBJ_IS_NOT_GLOBAL = PR_FALSE;
 struct JSObjectRefcounts;
 
 class nsXPConnect : public nsIXPConnect,
+                    public nsIThreadObserver,
                     public nsSupportsWeakReference,
                     public nsCycleCollectionLanguageRuntime,
                     public nsCycleCollectionParticipant
@@ -434,6 +437,7 @@ public:
     // all the interface method declarations...
     NS_DECL_ISUPPORTS
     NS_DECL_NSIXPCONNECT
+    NS_DECL_NSITHREADOBSERVER
 
     // non-interface implementation
 public:

xpcom/threads/Makefile.in

@@ -69,6 +69,7 @@ CPPSRCS		= \
 EXPORTS		= \
 		nsProcess.h \
 		nsEventQueue.h \
+		nsThreadUtilsInternal.h \
 		$(NULL)
 
 XPIDLSRCS	= \

xpcom/threads/nsThread.cpp

@@ -52,6 +52,8 @@ static PRLogModuleInfo *sLog = PR_NewLogModule("nsThread");
 
 NS_DECL_CI_INTERFACE_GETTER(nsThread)
 
+nsIThreadObserver* nsThread::sGlobalObserver;
+
 //-----------------------------------------------------------------------------
 // Because we do not have our own nsIFactory, we have to implement nsIClassInfo
 // somewhat manually.
@@ -464,6 +466,10 @@ nsThread::ProcessNextEvent(PRBool mayWait, PRBool *result)
 
   NS_ENSURE_STATE(PR_GetCurrentThread() == mThread);
 
+  if (sGlobalObserver) 
+    sGlobalObserver->OnProcessNextEvent(this, mayWait && !ShuttingDown(),
+                                        mRunningEvent);
+
   nsCOMPtr<nsIThreadObserver> obs = mObserver;
   if (obs)
     obs->OnProcessNextEvent(this, mayWait && !ShuttingDown(), mRunningEvent);
@@ -489,6 +495,9 @@ nsThread::ProcessNextEvent(PRBool mayWait, PRBool *result)
   if (obs)
     obs->AfterProcessNextEvent(this, mRunningEvent);
 
+  if (sGlobalObserver)
+    sGlobalObserver->AfterProcessNextEvent(this, mRunningEvent);
+
   return rv;
 }
 
@@ -618,3 +627,18 @@ nsThreadSyncDispatch::Run()
   }
   return NS_OK;
 }
+
+nsresult
+NS_SetGlobalThreadObserver(nsIThreadObserver* aObserver)
+{
+  if (aObserver && nsThread::sGlobalObserver) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+
+  if (!NS_IsMainThread()) {
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsThread::sGlobalObserver = aObserver;
+  return NS_OK;
+}

xpcom/threads/nsThread.h

@@ -72,6 +72,9 @@ public:
   // nsIThreadManager::NewThread.
   PRBool ShutdownRequired() { return mShutdownRequired; }
 
+  // The global thread observer
+  static nsIThreadObserver* sGlobalObserver;
+
 private:
   friend class nsThreadShutdownEvent;
 

xpcom/threads/nsThreadUtilsInternal.h

@@ -0,0 +1,61 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* ***** BEGIN LICENSE BLOCK *****
+ * Version: MPL 1.1/GPL 2.0/LGPL 2.1
+ *
+ * The contents of this file are subject to the Mozilla Public License Version
+ * 1.1 (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ * http://www.mozilla.org/MPL/
+ *
+ * Software distributed under the License is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
+ * for the specific language governing rights and limitations under the
+ * License.
+ *
+ * The Original Code is Mozilla code.
+ *
+ * The Initial Developer of the Original Code is the Mozilla Corporation.
+ * Portions created by the Initial Developer are Copyright (C) 2007
+ * the Initial Developer. All Rights Reserved.
+ *
+ * Contributor(s):
+ *  Boris Zbarsky <bzbarsky@mit.edu>
+ *
+ * Alternatively, the contents of this file may be used under the terms of
+ * either the GNU General Public License Version 2 or later (the "GPL"), or
+ * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
+ * in which case the provisions of the GPL or the LGPL are applicable instead
+ * of those above. If you wish to allow use of your version of this file only
+ * under the terms of either the GPL or the LGPL, and not to allow others to
+ * use your version of this file under the terms of the MPL, indicate your
+ * decision by deleting the provisions above and replace them with the notice
+ * and other provisions required by the GPL or the LGPL. If you do not delete
+ * the provisions above, a recipient may use your version of this file under
+ * the terms of any one of the MPL, the GPL or the LGPL.
+ *
+ * ***** END LICENSE BLOCK ***** */
+
+#ifndef nsThreadUtilsInternal_h_
+#define nsThreadUtilsInternal_h_
+
+#ifdef MOZILLA_INTERNAL_API
+
+class nsIThreadObserver;
+
+/**
+ * Function to set a "global" thread observer that all threads will notify when
+ * they process an event.  This observer will not be notified when events are
+ * posted to threads.  Only one global observer can be set at a time; an
+ * attempt to change the value without setting it to null first will throw.
+ * This function does NOT take a reference to the observer; the caller of this
+ * function is responsible for setting the observer to null when it goes away.
+ * This method may only be called on the main thread; attempts to do it on
+ * other threads will return an error.
+ */
+extern nsresult
+NS_COM NS_SetGlobalThreadObserver(nsIThreadObserver* aObserver);
+
+#endif // MOZILLA_INTERNAL_API
+
+#endif  // nsThreadUtilsInternal_h_