[PATCH 2/4] X event queue mutex

[Peter Hutterer]

On Tue, Nov 04, 2008 at 09:34:23AM -0800, Jeremy Huddleston wrote:
> <good>
> +        dev     = e->pDev;
> +        screen  = e->pScreen;
> +
>         miEventQueue.head = (miEventQueue.head + 1) % QUEUE_SIZE;
>
> +        type    = event->u.u.type;
> +        master  = (!dev->isMaster && dev->u.master) ? dev->u.master :  
> NULL;

>From 7693b94cd08030b9668130410104f432162f2859 Mon Sep 17 00:00:00 2001
From: Peter Hutterer <peter.hutterer at redhat.com>
Date: Tue, 4 Nov 2008 15:27:30 +1030
Subject: [PATCH] mi: clean up mieqProcessInputEvents, copy all events before processing.

Copy the EventRec's information into local variables before processing them,
this should make it safer for upcoming threading and also makes it easier to
read.

Simplify the event allocation code from the abyss it was before.

This also fixes a potential bug where a custom handler could scramble the
event before the same -now scrambled- event was then passed through the
master's custom event handler.

Signed-off-by: Peter Hutterer <peter.hutterer at redhat.com>
---
 mi/mieq.c |   98 ++++++++++++++++++++++++++++--------------------------------
 1 files changed, 46 insertions(+), 52 deletions(-)

diff --git a/mi/mieq.c b/mi/mieq.c
index 986e3a1..52bb841 100644
--- a/mi/mieq.c
+++ b/mi/mieq.c
@@ -307,8 +307,12 @@ mieqProcessInputEvents(void)
     mieqHandler handler;
     EventRec *e = NULL;
     int x = 0, y = 0;
-    xEvent* event,
-            *master_event = NULL;
+    int type, nevents, evlen, i;
+    ScreenPtr screen;
+    xEvent *event,
+           *master_event = NULL;
+    DeviceIntPtr dev = NULL,
+                 master = NULL;
 
     while (miEventQueue.head != miEventQueue.tail) {
         if (screenIsSaved == SCREEN_SAVER_ON)
@@ -322,79 +326,69 @@ mieqProcessInputEvents(void)
 #endif
 
         e = &miEventQueue.events[miEventQueue.head];
+
+        /* GenericEvents always have nevents == 1 */
+        nevents = e->nevents;
+        evlen   = (nevents > 1) ? sizeof(xEvent) : e->events->evlen;
+        event   = xcalloc(nevents, evlen);
+
+        if (!event)
+            FatalError("[mi] No memory left for event processing.\n");
+
+        for (i = 0; i < nevents; i++)
+            memcpy(&event[i], e->events[i].event, evlen);
+
+
+        dev     = e->pDev;
+        screen  = e->pScreen;
+
         miEventQueue.head = (miEventQueue.head + 1) % QUEUE_SIZE;
 
+        type    = event->u.u.type;
+        master  = (!dev->isMaster && dev->u.master) ? dev->u.master : NULL;
+
         /* Custom event handler */
-        handler = miEventQueue.handlers[e->events->event->u.u.type];
+        handler = miEventQueue.handlers[type];
 
-        if (e->pScreen != DequeueScreen(e->pDev) && !handler) {
+        if (screen != DequeueScreen(dev) && !handler) {
             /* Assumption - screen switching can only occur on motion events. */
-            DequeueScreen(e->pDev) = e->pScreen;
-            x = e->events[0].event->u.keyButtonPointer.rootX;
-            y = e->events[0].event->u.keyButtonPointer.rootY;
-            NewCurrentScreen (e->pDev, DequeueScreen(e->pDev), x, y);
+            DequeueScreen(dev) = screen;
+            x = event->u.keyButtonPointer.rootX;
+            y = event->u.keyButtonPointer.rootY;
+            NewCurrentScreen (dev, DequeueScreen(dev), x, y);
         }
         else {
-            /* FIXME: Bad hack. The only event where we actually get multiple
-             * events at once is a DeviceMotionNotify followed by
-             * DeviceValuators. For now it's safe enough to just take the
-             * event directly or copy the bunch of events and pass in the
-             * copy. Eventually the interface for the processInputProc needs
-             * to be changed. (whot)
-             */
-            if (e->nevents > 1)
-            {
-                int i;
-                event = xcalloc(e->nevents, sizeof(xEvent));
-                if (!event)
-                    FatalError("[mi] No memory left for event processing.\n");
-                for (i = 0; i < e->nevents; i++)
-                {
-                    memcpy(&event[i], e->events[i].event, sizeof(xEvent));
-                }
-            } else
-                event = e->events->event;
-            if (!e->pDev->isMaster && e->pDev->u.master)
-            {
-                CopyGetMasterEvent(e->pDev->u.master, event,
-                                   &master_event, e->nevents);
-            } else
+            if (master)
+                CopyGetMasterEvent(master, event,
+                                   &master_event, nevents);
+            else
                 master_event = NULL;
 
             /* If someone's registered a custom event handler, let them
              * steal it. */
             if (handler)
             {
-                handler(DequeueScreen(e->pDev)->myNum, e->events->event,
-                        e->pDev, e->nevents);
-                if (!e->pDev->isMaster && e->pDev->u.master)
-                {
-                    handler(DequeueScreen(e->pDev->u.master)->myNum,
-                            e->events->event, e->pDev->u.master, e->nevents);
-                }
+                handler(DequeueScreen(dev)->myNum, event, dev, nevents);
+                if (master)
+                    handler(DequeueScreen(master)->myNum,
+                            master_event, master, nevents);
             } else
             {
                 /* process slave first, then master */
-                e->pDev->public.processInputProc(event, e->pDev, e->nevents);
+                dev->public.processInputProc(event, dev, nevents);
 
-                if (!e->pDev->isMaster && e->pDev->u.master)
-                {
-                    e->pDev->u.master->public.processInputProc(master_event,
-                            e->pDev->u.master, e->nevents);
-                }
+                if (master)
+                    master->public.processInputProc(master_event, master,
+                                                    nevents);
             }
 
-            if (e->nevents > 1)
-                xfree(event);
+            xfree(event);
             xfree(master_event);
         }
 
         /* Update the sprite now. Next event may be from different device. */
-        if (e->events->event[0].u.u.type == DeviceMotionNotify
-                && e->pDev->coreEvents)
-        {
-            miPointerUpdateSprite(e->pDev);
-        }
+        if (type == DeviceMotionNotify && dev->coreEvents)
+            miPointerUpdateSprite(dev);
     }
 }
 
-- 
1.6.0.3