Back out bug 1191145 - Stop blocking scripts in CPOW IPCs

dom/ipc/ContentChild.cpp

@@ -648,6 +648,10 @@ ContentChild::Init(MessageLoop* aIOLoop,
     }
     sSingleton = this;
 
+    // Make sure there's an nsAutoScriptBlocker on the stack when dispatching
+    // urgent messages.
+    GetIPCChannel()->BlockScripts();
+
     // If communications with the parent have broken down, take the process
     // down so it's not hanging around.
     bool abortOnError = true;

ipc/glue/MessageChannel.cpp

@@ -275,6 +275,31 @@ private:
     CxxStackFrame& operator=(const CxxStackFrame&) = delete;
 };
 
+namespace {
+
+class MOZ_RAII MaybeScriptBlocker {
+public:
+    explicit MaybeScriptBlocker(MessageChannel *aChannel, bool aBlock
+                                MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
+        : mBlocked(aChannel->ShouldBlockScripts() && aBlock)
+    {
+        MOZ_GUARD_OBJECT_NOTIFIER_INIT;
+        if (mBlocked) {
+            nsContentUtils::AddScriptBlocker();
+        }
+    }
+    ~MaybeScriptBlocker() {
+        if (mBlocked) {
+            nsContentUtils::RemoveScriptBlocker();
+        }
+    }
+private:
+    MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
+    bool mBlocked;
+};
+
+} // namespace
+
 MessageChannel::MessageChannel(MessageListener *aListener)
   : mListener(aListener),
     mChannelState(ChannelClosed),
@@ -300,6 +325,7 @@ MessageChannel::MessageChannel(MessageListener *aListener)
     mSawInterruptOutMsg(false),
     mIsWaitingForIncoming(false),
     mAbortOnError(false),
+    mBlockScripts(false),
     mFlags(REQUIRE_DEFAULT),
     mPeerPidSet(false),
     mPeerPid(-1)
@@ -815,6 +841,9 @@ MessageChannel::Send(Message* aMsg, Message* aReply)
 {
     nsAutoPtr<Message> msg(aMsg);
 
+    // See comment in DispatchSyncMessage.
+    MaybeScriptBlocker scriptBlocker(this, true);
+
     // Sanity checks.
     AssertWorkerThread();
     mMonitor->AssertNotCurrentThreadOwns();
@@ -1296,7 +1325,13 @@ MessageChannel::DispatchSyncMessage(const Message& aMsg, Message*& aReply)
     AssertWorkerThread();
 
     int prio = aMsg.priority();
+
+    // We don't want to run any code that might run a nested event loop here, so
+    // we avoid running event handlers. Once we've sent the response to the
+    // urgent message, it's okay to run event handlers again since the parent is
+    // no longer blocked.
     MOZ_ASSERT_IF(prio > IPC::Message::PRIORITY_NORMAL, NS_IsMainThread());
+    MaybeScriptBlocker scriptBlocker(this, prio > IPC::Message::PRIORITY_NORMAL);
 
     MessageChannel* dummy;
     MessageChannel*& blockingVar = NS_IsMainThread() ? gMainThreadBlocker : dummy;
@@ -1854,6 +1889,13 @@ MessageChannel::CloseWithTimeout()
     mChannelState = ChannelTimeout;
 }
 
+void
+MessageChannel::BlockScripts()
+{
+    MOZ_ASSERT(NS_IsMainThread());
+    mBlockScripts = true;
+}
+
 void
 MessageChannel::Close()
 {

ipc/glue/MessageChannel.h

@@ -107,6 +107,13 @@ class MessageChannel : HasResultCodes
     void SetChannelFlags(ChannelFlags aFlags) { mFlags = aFlags; }
     ChannelFlags GetChannelFlags() { return mFlags; }
 
+    void BlockScripts();
+
+    bool ShouldBlockScripts() const
+    {
+        return mBlockScripts;
+    }
+
     // Asynchronously send a message to the other side of the channel
     bool Send(Message* aMsg);
 
@@ -729,6 +736,9 @@ class MessageChannel : HasResultCodes
     // a channel error occurs?
     bool mAbortOnError;
 
+    // Should we prevent scripts from running while dispatching urgent messages?
+    bool mBlockScripts;
+
     // See SetChannelFlags
     ChannelFlags mFlags;