dix: dixutils: make workQueue pointer dix-private

The workQueue pointer is currently declared extern, so that WaitForSomething()
can check wether we've got something in the queue and call ProcessWorkQueue()
then.

But that's trivial to simplify: just let ProcessWorkQueue() return early if
workQueue == NULL. Gives us a better isolation of internal stuff as well as
ProcessWorkQueue() protecting itself from possible segfault.

Signed-off-by: Enrico Weigelt, metux IT consult <info@metux.net>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/1310>

dix/dixutils.c

@@ -525,6 +525,10 @@ ProcessWorkQueue(void)
 {
     WorkQueuePtr q, *p;
 
+    // don't have a work queue yet
+    if (!workQueue)
+        return;
+
     p = &workQueue;
     /*
      * Scan the work queue once, calling each function.  Those

doc/Xserver-spec.xml

@@ -657,14 +657,11 @@ make the server suspend until one or more of the following occurs:
 <para>
 Before WaitForSomething() computes the masks to pass to select, poll or
 similar operating system interface, it needs to
-see if there is anything to do on the work queue; if so, it must call a DIX
-routine called ProcessWorkQueue.
+see if there is anything to do on the work queue; it must call a DIX
+routine called ProcessWorkQueue().
 <blockquote>
 <programlisting>
-	extern WorkQueuePtr	workQueue;
-
-	if (workQueue)
-		ProcessWorkQueue ();
+	ProcessWorkQueue ();
 </programlisting>
 </blockquote>
 </para>

os/WaitFor.c

@@ -188,9 +188,7 @@ WaitForSomething(Bool are_ready)
        crashed connections and the screen saver timeout */
     while (1) {
         /* deal with any blocked jobs */
-        if (workQueue) {
-            ProcessWorkQueue();
-        }
+        ProcessWorkQueue();
 
         timeout = check_timers();
         are_ready = clients_are_ready();

os/osdep.h

@@ -123,8 +123,6 @@ listen_to_client(ClientPtr client);
 
 extern Bool NewOutputPending;
 
-extern WorkQueuePtr workQueue;
-
 /* in access.c */
 extern Bool ComputeLocalClient(ClientPtr client);