Ensure that rotation updates happen frequently

The smart scheduler is designed to minimize scheduler overhead by
increasing the interval between WaitForSomething calls when a single
client is running. However, the software rotation code depends on
its BlockHandler being invoked for screen updates; the long delays
caused by the smart scheduler optimizations means that screen updates
can be delayed a long time as well.

The change is simple -- prevent the smart scheduler from increasing
the scheduling interval while any screen is using software rotation.

Signed-off-by: Keith Packard <keithp@keithp.com>

3 files changed, 29 insertions, 1 deletions

diff --git a/dix/dispatch.c b/dix/dispatch.c
index 31c69612b..414bd0404 100644
--- a/dix/dispatch.c
+++ b/dix/dispatch.c
@@ -239,12 +239,13 @@ UpdateCurrentTimeIf(void)
 
 Bool SmartScheduleDisable = FALSE;
 long SmartScheduleSlice = SMART_SCHEDULE_DEFAULT_INTERVAL;
 long SmartScheduleInterval = SMART_SCHEDULE_DEFAULT_INTERVAL;
 long SmartScheduleMaxSlice = SMART_SCHEDULE_MAX_SLICE;
 long SmartScheduleTime;
+int SmartScheduleLatencyLimited = 0;
 static ClientPtr   SmartLastClient;
 static int	   SmartLastIndex[SMART_MAX_PRIORITY-SMART_MIN_PRIORITY+1];
 
 #ifdef SMART_DEBUG
 long	    SmartLastPrint;
 #endif
@@ -309,13 +310,13 @@ SmartScheduleClient (int *clientReady, int nready)
 	pClient->smart_start_tick = now;
 	SmartLastClient = pClient;
     }
     /*
      * Adjust slice
      */
-    if (nready == 1)
+    if (nready == 1 && SmartScheduleLatencyLimited == 0)
     {
 	/*
 	 * If it's been a long time since another client
 	 * has run, bump the slice up to get maximal
 	 * performance from a single client
 	 */
@@ -329,12 +330,29 @@ SmartScheduleClient (int *clientReady, int nready)
     {
 	SmartScheduleSlice = SmartScheduleInterval;
     }
     return best;
 }
 
+void
+EnableLimitedSchedulingLatency(void)
+{
+    ++SmartScheduleLatencyLimited;
+    SmartScheduleSlice = SmartScheduleInterval;
+}
+
+void
+DisableLimitedSchedulingLatency(void)
+{
+    --SmartScheduleLatencyLimited;
+
+    /* protect against bugs */
+    if (SmartScheduleLatencyLimited < 0)
+	SmartScheduleLatencyLimited = 0;
+}
+
 #define MAJOROP ((xReq *)client->requestBuffer)->reqType
 
 void
 Dispatch(void)
 {
     int        *clientReady;     /* array of request ready clients */
@@ -348,12 +366,13 @@ Dispatch(void)
     nClients = 0;
 
     clientReady = xalloc(sizeof(int) * MaxClients);
     if (!clientReady)
 	return;
 
+    SmartScheduleSlice = SmartScheduleInterval;
     while (!dispatchException)
     {
         if (*icheck[0] != *icheck[1])
 	{
 	    ProcessInputEvents();
 	    FlushIfCriticalOutputPending();
@@ -452,12 +471,13 @@ Dispatch(void)
 #if defined(DDXBEFORERESET)
     ddxBeforeReset ();
 #endif
     KillAllClients();
     xfree(clientReady);
     dispatchException &= ~DE_RESET;
+    SmartScheduleLatencyLimited = 0;
 }
 
 #undef MAJOROP
 
 static int  VendorRelease = VENDOR_RELEASE;
 static char *VendorString = VENDOR_NAME;
diff --git a/hw/xfree86/modes/xf86Rotate.c b/hw/xfree86/modes/xf86Rotate.c
index e0ea274a2..d9face1cb 100644
--- a/hw/xfree86/modes/xf86Rotate.c
+++ b/hw/xfree86/modes/xf86Rotate.c
@@ -225,12 +225,13 @@ xf86RotatePrepare (ScreenPtr pScreen)
 	    if (!xf86_config->rotation_damage_registered)
 	    {
 		/* Hook damage to screen pixmap */
 		DamageRegister (&(*pScreen->GetScreenPixmap)(pScreen)->drawable,
 				xf86_config->rotation_damage);
 		xf86_config->rotation_damage_registered = TRUE;
+		EnableLimitedSchedulingLatency();
 	    }
 	    
 	    xf86CrtcDamageShadow (crtc);
 	}
     }
 }
@@ -335,12 +336,13 @@ xf86RotateDestroy (xf86CrtcPtr crtc)
 	/* Free damage structure */
 	if (xf86_config->rotation_damage_registered)
 	{
 	    DamageUnregister (&(*pScreen->GetScreenPixmap)(pScreen)->drawable,
 			      xf86_config->rotation_damage);
 	    xf86_config->rotation_damage_registered = FALSE;
+	    DisableLimitedSchedulingLatency();
 	}
 	DamageDestroy (xf86_config->rotation_damage);
 	xf86_config->rotation_damage = NULL;
     }
 }
 
diff --git a/include/dix.h b/include/dix.h
index e2db6b655..49dfe3774 100644
--- a/include/dix.h
+++ b/include/dix.h
@@ -226,12 +226,18 @@ extern _X_EXPORT void BlockHandler(
     pointer /*pReadmask*/);
 
 extern _X_EXPORT void WakeupHandler(
     int /*result*/,
     pointer /*pReadmask*/);
 
+void
+EnableLimitedSchedulingLatency(void);
+
+void
+DisableLimitedSchedulingLatency(void);
+
 typedef void (* WakeupHandlerProcPtr)(
     pointer /* blockData */,
     int /* result */,
     pointer /* pReadmask */);
 
 extern _X_EXPORT Bool RegisterBlockAndWakeupHandlers(