mieq: Reserve some space in EQ for release and other special events

The last 64 events in the event queue will be reserved for release
events in order to help return the system to a cleaner state when
it comes back from a soft wedge.

Signed-off-by: Jeremy Huddleston <jeremyhu@apple.com>
Reviewed-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 29 insertions, 4 deletions

diff --git a/mi/mieq.c b/mi/mieq.c
index f644658fd..093dba20f 100644
--- a/mi/mieq.c
+++ b/mi/mieq.c
@@ -60,7 +60,8 @@ in this Software without prior written authorization from The Open Group.
 #endif
 
 /* Maximum size should be initial size multiplied by a power of 2 */
-#define QUEUE_INITIAL_SIZE                 128
+#define QUEUE_INITIAL_SIZE                 256
+#define QUEUE_RESERVED_SIZE                 64
 #define QUEUE_MAXIMUM_SIZE                4096
 #define QUEUE_DROP_BACKTRACE_FREQUENCY     100
 #define QUEUE_DROP_BACKTRACE_MAX            10
@@ -205,6 +206,26 @@ mieqFini(void)
     free(miEventQueue.events);
 }
 
+/* This function will determine if the given event is allowed to used the reserved
+ * queue space.
+ */
+static Bool
+mieqReservedCandidate(InternalEvent *e) {
+    switch(e->any.type) {
+        case ET_KeyRelease:
+        case ET_ButtonRelease:
+#if XFreeXDGA
+        case ET_DGAEvent:
+#endif
+        case ET_RawKeyRelease:
+        case ET_RawButtonRelease:
+        case ET_XQuartz:
+            return TRUE;
+        default:
+            return FALSE;
+    }
+}
+
 /*
  * Must be reentrant with ProcessInputEvents.  Assumption: mieqEnqueue
  * will never be interrupted.  If this is called from both signal
@@ -220,6 +241,7 @@ mieqEnqueue(DeviceIntPtr pDev, InternalEvent *e)
     int                    isMotion = 0;
     int                    evlen;
     Time                   time;
+    size_t                 n_enqueued;
 
 #ifdef XQUARTZ
     wait_for_server_init();
@@ -228,6 +250,8 @@ mieqEnqueue(DeviceIntPtr pDev, InternalEvent *e)
 
     verify_internal_event(e);
 
+    n_enqueued = mieqNumEnqueued(&miEventQueue);
+
     /* avoid merging events from different devices */
     if (e->any.type == ET_Motion)
         isMotion = pDev->id;
@@ -235,7 +259,8 @@ mieqEnqueue(DeviceIntPtr pDev, InternalEvent *e)
     if (isMotion && isMotion == miEventQueue.lastMotion &&
         oldtail != miEventQueue.head) {
         oldtail = (oldtail - 1) % miEventQueue.nevents;
-    } else if (((oldtail + 1) % miEventQueue.nevents) == miEventQueue.head) {
+    } else if ((n_enqueued + 1 == miEventQueue.nevents) ||
+               ((n_enqueued + 1 >= miEventQueue.nevents - QUEUE_RESERVED_SIZE) && !mieqReservedCandidate(e))) {
         /* Toss events which come in late.  Usually this means your server's
          * stuck in an infinite loop somewhere, but SIGIO is still getting
          * handled.
@@ -517,9 +542,9 @@ mieqProcessInputEvents(void)
     pthread_mutex_lock(&miEventQueueMutex);
 #endif
 
-    /* Grow our queue if we are reaching capacity: > 50% full */
+    /* Grow our queue if we are reaching capacity: < 2 * QUEUE_RESERVED_SIZE remaining */
     n_enqueued = mieqNumEnqueued(&miEventQueue);
-    if (n_enqueued >= (miEventQueue.nevents >> 1) &&
+    if (n_enqueued >= (miEventQueue.nevents - (2 * QUEUE_RESERVED_SIZE)) &&
         miEventQueue.nevents < QUEUE_MAXIMUM_SIZE) {
         ErrorF("[mi] Increasing EQ size to %lu to prevent dropped events.\n", miEventQueue.nevents << 1);
         if (!mieqGrowQueue(&miEventQueue, miEventQueue.nevents << 1)) {