Re: 2.6.32.2: undefined reference to `__udivdi3'

Stephen Hemminger
2009-12-21T20:21:55Z

The new menu governor driver is written by Intel folks who never use 32-bit
anymore it seems :-)
---------------------------------------------------------
Subject: [PATCH] menu: use proper 64 bit math

The new menu governor is incorrectly doing a 64 bit divide.
Compile tested only

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>

--- a/drivers/cpuidle/governors/menu.c 2009-12-21 12:02:25.840083589 -0800
+++ b/drivers/cpuidle/governors/menu.c 2009-12-21 12:16:42.418834255 -0800
@@ -18,6 +18,7 @@
#include <linux/hrtimer.h>
#include <linux/tick.h>
#include <linux/sched.h>
+#include <linux/math64.h>

#define BUCKETS 12
#define RESOLUTION 1024
@@ -169,6 +170,12 @@ static DEFINE_PER_CPU(struct menu_device

static void menu_update(struct cpuidle_device *dev);

+/* This implements DIV_ROUND_CLOSEST but avoids 64 bit division */
+static u64 div_round64(u64 dividend, u32 divisor)
+{
+ return div_u64(dividend + (divisor / 2), divisor);
+}
+
/**
* menu_select - selects the next idle state to enter
* @dev: the CPU
@@ -209,9 +216,8 @@ static int menu_select(struct cpuidle_de
data->correction_factor[data->bucket] = RESOLUTION * DECAY;

/* Make sure to round up for half microseconds */
- data->predicted_us = DIV_ROUND_CLOSEST(
- data->expected_us * data->correction_factor[data->bucket],
- RESOLUTION * DECAY);
+ data->predicted_us = div_round64(data->expected_us * data->correction_factor[data->bucket],
+ RESOLUTION * DECAY);

/*
* We want to default to C1 (hlt), not to busy polling