From eca731ac63f6bfef57c674c8ce2fba90fbb34cc4 Mon Sep 17 00:00:00 2001
From: peter <peter@FreeBSD.org>
Date: Sat, 12 Mar 2005 00:10:23 +0000
Subject: [PATCH] Make the tty vmin/vtime timeouts work for hz > 169 on 32 bit
 machines.

---
 sys/kern/tty.c | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/sys/kern/tty.c b/sys/kern/tty.c
index f916a1bfe674..bc95f0423c42 100644
--- a/sys/kern/tty.c
+++ b/sys/kern/tty.c
@@ -97,6 +97,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/poll.h>
 #include <sys/kernel.h>
 #include <sys/vnode.h>
+#include <sys/limits.h>
 #include <sys/serial.h>
 #include <sys/signalvar.h>
 #include <sys/resourcevar.h>
@@ -1854,14 +1855,13 @@ loop:
 #undef diff
 		/*
 		 * Rounding down may make us wake up just short
-		 * of the target, so we round up.
-		 * The formula is ceiling(slp * hz/1000000).
-		 * 32-bit arithmetic is enough for hz < 169.
-		 * XXX see tvtohz() for how to avoid overflow if hz
-		 * is large (divide by `tick' and/or arrange to
-		 * use tvtohz() if hz is large).
+		 * of the target, so we round up.  The 32 bit arithmetic is
+		 * sufficient for the first calculation for hz < 169.
 		 */
-		slp = (long) (((u_long)slp * hz) + 999999) / 1000000;
+		if (sizeof(u_long) > 4 || slp <= ULONG_MAX / hz)
+			slp = (long) (((u_long)slp * hz) + 999999) / 1000000;
+		else
+			slp = (slp + (tick - 1)) / tick;
 		goto sleep;
 	}
 	if (qp->c_cc <= 0) {