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

[YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@linux-ipv6.org>]

Hello.

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

Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

diff --git a/kernel/timer.c b/kernel/timer.c
--- 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)

-- 
YOSHIFUJI Hideaki @ USAGI Project  <yoshfuji@linux-ipv6.org>
GPG-FP  : 9022 65EB 1ECF 3AD1 0BDF  80D8 4807 F894 E062 0EEA
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