From 3e5f626dd16279ae576e035cc086cb2caa07244d Mon Sep 17 00:00:00 2001
From: gibbs <gibbs@FreeBSD.org>
Date: Wed, 24 Sep 1997 16:39:27 +0000
Subject: Store an absolute tick value in callout entries so that a subtraction
 on hash chain traversal isn't needed.  This also allows untimeout to
 recompute the hash to find the bucket that the entry to remove is stored in
 so that each callout entry no longer needs to store that information.

Reviewed by:	 Nate Williams <nate@mt.sri.com>
---
 sys/kern/kern_timeout.c | 28 ++++++++++++++++++----------
 1 file changed, 18 insertions(+), 10 deletions(-)

(limited to 'sys/kern/kern_timeout.c')

diff --git a/sys/kern/kern_timeout.c b/sys/kern/kern_timeout.c
index b14c552..f1b30b5 100644
--- a/sys/kern/kern_timeout.c
+++ b/sys/kern/kern_timeout.c
@@ -36,7 +36,7 @@
  * SUCH DAMAGE.
  *
  *	@(#)kern_clock.c	8.5 (Berkeley) 1/21/94
- * $Id: kern_clock.c,v 1.40 1997/09/07 05:25:43 bde Exp $
+ * $Id: kern_clock.c,v 1.41 1997/09/21 22:00:07 gibbs Exp $
  */
 
 /* Portions of this software are covered by the following: */
@@ -696,7 +696,9 @@ void
 softclock()
 {
 	register struct callout *c;
+	register struct callout_tailq *bucket;
 	register int s;
+	register int curticks;
 	register int steps;	/*
 				 * Number of steps taken since
 				 * we last allowed interrupts.
@@ -709,16 +711,22 @@ softclock()
 	steps = 0;
 	s = splhigh();
 	while (softticks != ticks) {
-		c = TAILQ_FIRST(&callwheel[++softticks & callwheelmask]);
+		softticks++;
+		/*
+		 * softticks may be modified by hard clock, so cache
+		 * it while we work on a given bucket.
+		 */
+		curticks = softticks;
+		bucket = &callwheel[curticks & callwheelmask];
+		c = TAILQ_FIRST(bucket);
 		while (c) {
-			if (c->c_time > 0) {
-				c->c_time--;
+			if (c->c_time != curticks) {
 				c = TAILQ_NEXT(c, c_links.tqe);
 				++steps;
 				if (steps >= MAX_SOFTCLOCK_STEPS) {
 					nextsoftcheck = c;
+					/* Give interrupts a chance. */
 					splx(s);
-					/* Give hardclock() a chance. */
 					s = splhigh();
 					c = nextsoftcheck;
 					steps = 0;
@@ -728,7 +736,7 @@ softclock()
 				void *c_arg;
 
 				nextsoftcheck = TAILQ_NEXT(c, c_links.tqe);
-				TAILQ_REMOVE(c->c_bucket, c, c_links.tqe);
+				TAILQ_REMOVE(bucket, c, c_links.tqe);
 				c_func = c->c_func;
 				c_arg = c->c_arg;
 				c->c_func = NULL;
@@ -786,9 +794,9 @@ timeout(ftn, arg, to_ticks)
 	SLIST_REMOVE_HEAD(&callfree, c_links.sle);
 	new->c_arg = arg;
 	new->c_func = ftn;
-	new->c_time = to_ticks >> callwheelbits;
-	new->c_bucket = &callwheel[(ticks + to_ticks) & callwheelmask];
-	TAILQ_INSERT_TAIL(new->c_bucket, new, c_links.tqe);
+	new->c_time = ticks + to_ticks;
+	TAILQ_INSERT_TAIL(&callwheel[new->c_time & callwheelmask],
+			  new, c_links.tqe);
 
 	splx(s);
 	handle.callout = new;
@@ -818,7 +826,7 @@ untimeout(ftn, arg, handle)
 		if (nextsoftcheck == handle.callout) {
 			nextsoftcheck = TAILQ_NEXT(handle.callout, c_links.tqe);
 		}
-		TAILQ_REMOVE(handle.callout->c_bucket,
+		TAILQ_REMOVE(&callwheel[handle.callout->c_time & callwheelmask],
 			     handle.callout, c_links.tqe);
 		handle.callout->c_func = NULL;
 		SLIST_INSERT_HEAD(&callfree, handle.callout, c_links.sle);
-- 
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