From 4db4a1313e2992ffb77949f4fbd7fff16ffceaee Mon Sep 17 00:00:00 2001

From: Adam Jackson <ajax@redhat.com>

Date: Wed, 10 Dec 2008 16:13:20 -0500

Subject: [PATCH] xsync: Fix wakeup storm in idletime counter.

Wakeup scheduling only considered the threshold values, and not whether

the trigger was edge or level.

---

 Xext/sync.c |   51 +++++++++++++++++++++++++++++++++++++++++----------

 1 files changed, 41 insertions(+), 10 deletions(-)

diff --git a/Xext/sync.c b/Xext/sync.c

index d6b8c27..4d159d2 100644

--- a/Xext/sync.c

+++ b/Xext/sync.c

@@ -2323,7 +2323,7 @@ SyncInitServerTime(void)

  * IDLETIME implementation

  */

-static pointer IdleTimeCounter;

+static SyncCounter *IdleTimeCounter;

 static XSyncValue *pIdleTimeValueLess;

 static XSyncValue *pIdleTimeValueGreater;

@@ -2335,38 +2335,69 @@ IdleTimeQueryValue (pointer pCounter, CARD64 *pValue_return)

 }

 static void

-IdleTimeBlockHandler (pointer env,

-                      struct timeval **wt,

-                      pointer LastSelectMask)

+IdleTimeBlockHandler(pointer env, struct timeval **wt, pointer LastSelectMask)

 {

-    XSyncValue idle;

+    XSyncValue idle, old_idle;

+    SyncTriggerList *list = IdleTimeCounter->pTriglist;

+    SyncTrigger *trig;

     if (!pIdleTimeValueLess && !pIdleTimeValueGreater)

 	return;

+    old_idle = IdleTimeCounter->value;

     IdleTimeQueryValue (NULL, &idle);

+    IdleTimeCounter->value = idle; /* push, so CheckTrigger works */

     if (pIdleTimeValueLess &&

         XSyncValueLessOrEqual (idle, *pIdleTimeValueLess))

     {

-	AdjustWaitForDelay (wt, 0);

+	/*

+	 * We've been idle for less than the threshold value, and someone

+	 * wants to know about that, but now we need to know whether they

+	 * want level or edge trigger.  Check the trigger list against the

+	 * current idle time, and if any succeed, bomb out of select()

+	 * immediately so we can reschedule.

+	 */

+

+	for (list = IdleTimeCounter->pTriglist; list; list = list->next) {

+	    trig = list->pTrigger;

+	    if (trig->CheckTrigger(trig, old_idle)) {

+		AdjustWaitForDelay(wt, 0);

+		break;

+	    }

+	}

     }

     else if (pIdleTimeValueGreater)

     {

-	unsigned long timeout = 0;

+	/*

+	 * There's a threshold in the positive direction.  If we've been

+	 * idle less than it, schedule a wakeup for sometime in the future.

+	 * If we've been idle more than it, and someone wants to know about

+	 * that level-triggered, schedule an immediate wakeup.

+	 */

+	unsigned long timeout = -1;

-	if (XSyncValueLessThan (idle, *pIdleTimeValueGreater))

-	{

+	if (XSyncValueLessThan (idle, *pIdleTimeValueGreater)) {

 	    XSyncValue value;

 	    Bool overflow;

 	    XSyncValueSubtract (&value, *pIdleTimeValueGreater,

 	                        idle, &overflow);

-	    timeout = XSyncValueLow32 (value);

+	    timeout = min(timeout, XSyncValueLow32 (value));

+	} else {

+	    for (list = IdleTimeCounter->pTriglist; list; list = list->next) {

+		trig = list->pTrigger;

+		if (trig->CheckTrigger(trig, old_idle)) {

+		    timeout = min(timeout, 0);

+		    break;

+		}

+	    }

 	}

 	AdjustWaitForDelay (wt, timeout);

     }

+

+    IdleTimeCounter->value = old_idle; /* pop */

 }

 static void

-- 

1.6.0.3