[PATCH] sqrt() fixes

It turns out that the int_sqrt() function in oom_kill.c gets it wrong.

But fb_sqrt() in fbmon.c gets its math right.  Move that function into
lib/int_sqrt.c, and consolidate.

(oom_kill.c fix from Thomas Schlichter <schlicht@uni-mannheim.de>)

drivers/video/fbmon.c

@@ -890,30 +890,6 @@ struct __fb_timings {
 	u32 vtotal;
 };
 
-/*
- * a simple function to get the square root of integers 
- */
-static u32 fb_sqrt(int x)
-{
-	register int op, res, one;
-
-	op = x;
-	res = 0;
-
-	one = 1 << 30;
-	while (one > op) one >>= 2;
-
-	while (one != 0) {
-		if (op >= res + one) {
-			op = op - (res + one);
-			res = res +  2 * one;
-		}
-		res /= 2;
-		one /= 4;
-	}
-	return((u32) res);
-}
-
 /**
  * fb_get_vblank - get vertical blank time
  * @hfreq: horizontal freq
@@ -1002,7 +978,7 @@ static u32 fb_get_hblank_by_dclk(u32 dclk, u32 xres)
 	h_period += (M_VAL * xres * 2 * 1000)/(5 * dclk);
 	h_period *=10000; 
 
-	h_period = fb_sqrt((int) h_period);
+	h_period = int_sqrt(h_period);
 	h_period -= (100 - C_VAL) * 100;
 	h_period *= 1000; 
 	h_period /= 2 * M_VAL;

include/linux/kernel.h

@@ -87,6 +87,8 @@ extern int session_of_pgrp(int pgrp);
 asmlinkage int printk(const char * fmt, ...)
 	__attribute__ ((format (printf, 1, 2)));
 
+unsigned long int_sqrt(unsigned long);
+
 static inline void console_silent(void)
 {
 	console_loglevel = 0;

lib/Makefile

@@ -5,7 +5,7 @@
 
 lib-y := errno.o ctype.o string.o vsprintf.o cmdline.o \
 	 bust_spinlocks.o rbtree.o radix-tree.o dump_stack.o \
-	 kobject.o idr.o div64.o parser.o
+	 kobject.o idr.o div64.o parser.o int_sqrt.o
 
 lib-$(CONFIG_RWSEM_GENERIC_SPINLOCK) += rwsem-spinlock.o
 lib-$(CONFIG_RWSEM_XCHGADD_ALGORITHM) += rwsem.o

lib/int_sqrt.c

+
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+/**
+ * int_sqrt - rough approximation to sqrt
+ * @x: integer of which to calculate the sqrt
+ *
+ * A very rough approximation to the sqrt() function.
+ */
+unsigned long int_sqrt(unsigned long x)
+{
+	unsigned long op, res, one;
+
+	op = x;
+	res = 0;
+
+	one = 1 << 30;
+	while (one > op)
+		one >>= 2;
+
+	while (one != 0) {
+		if (op >= res + one) {
+			op = op - (res + one);
+			res = res +  2 * one;
+		}
+		res /= 2;
+		one /= 4;
+	}
+	return res;
+}
+EXPORT_SYMBOL(int_sqrt);

mm/oom_kill.c

@@ -23,20 +23,6 @@
 
 /* #define DEBUG */
 
-/**
- * int_sqrt - oom_kill.c internal function, rough approximation to sqrt
- * @x: integer of which to calculate the sqrt
- * 
- * A very rough approximation to the sqrt() function.
- */
-static unsigned int int_sqrt(unsigned int x)
-{
-	unsigned int out = x;
-	while (x & ~(unsigned int)1) x >>=2, out >>=1;
-	if (x) out -= out >> 2;
-	return (out ? out : 1);
-}	
-
 /**
  * oom_badness - calculate a numeric value for how bad this task has been
  * @p: task struct of which task we should calculate
@@ -57,7 +43,7 @@ static unsigned int int_sqrt(unsigned int x)
 
 static int badness(struct task_struct *p)
 {
-	int points, cpu_time, run_time;
+	int points, cpu_time, run_time, s;
 
 	if (!p->mm)
 		return 0;
@@ -77,8 +63,12 @@ static int badness(struct task_struct *p)
 	cpu_time = (p->utime + p->stime) >> (SHIFT_HZ + 3);
 	run_time = (get_jiffies_64() - p->start_time) >> (SHIFT_HZ + 10);
 
-	points /= int_sqrt(cpu_time);
-	points /= int_sqrt(int_sqrt(run_time));
+	s = int_sqrt(cpu_time);
+	if (s)
+		points /= s;
+	s = int_sqrt(int_sqrt(run_time));
+	if (s)
+		points /= s;
 
 	/*
 	 * Niced processes are most likely less important, so double