From: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Date: Sun, 30 Oct 2005 01:15:42 +0000 (-0700)
Subject: [PATCH] TIMERS: add missing compensation for HZ == 250
X-Git-Tag: v2.6.15-rc1~730^2^2~85
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=4b8f573b5db02a3017afbba49026a6aef480174f;p=linux-2.6

[PATCH] TIMERS: add missing compensation for HZ == 250

Add missing compensation for (HZ == 250) != (1 << SHIFT_HZ) in
second_overflow().

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---

diff --git a/kernel/timer.c b/kernel/timer.c
index 3ba10fa35b..6a2e5f8dc7 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -752,6 +752,15 @@ static void second_overflow(void)
     else
 	time_adj += (time_adj >> 2) + (time_adj >> 5);
 #endif
+#if HZ == 250
+    /* Compensate for (HZ==250) != (1 << SHIFT_HZ).
+     * Add 1.5625% and 0.78125% to get 255.85938; => only 0.05% error (p. 14)
+     */
+    if (time_adj < 0)
+	time_adj -= (-time_adj >> 6) + (-time_adj >> 7);
+    else
+	time_adj += (time_adj >> 6) + (time_adj >> 7);
+#endif
 #if HZ == 1000
     /* Compensate for (HZ==1000) != (1 << SHIFT_HZ).
      * Add 1.5625% and 0.78125% to get 1023.4375; => only 0.05% error (p. 14)