Message-Id: <200912080319.30679.rob@landley.net>
Date:	Tue, 8 Dec 2009 03:19:30 -0600
From:	Rob Landley <rob@...dley.net>
To:	linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] Replace kernel/timeconst.pl with kernel/timeconst.sh

From: Rob Landley <rob@...dley.net>

Replace kernel/timeconst.pl with kernel/timeconst.sh. The new shell script
is much simpler, about 1/4 the size, and runs on Red Hat 9 from 2003.

Signed-off-by: Rob Landley <rob@...dley.net>
--

kernel/Makefile | 4
kernel/timeconst.pl | 378 ------------------------------------------
kernel/timeconst.sh | 91 ++++++++++
3 files changed, 93 insertions(+), 380 deletions(-)

diff -ruN linux-2.6.30/kernel/Makefile linux-2.6.30.new/kernel/Makefile
--- linux-2.6.30/kernel/Makefile	2009-06-09 22:05:27.000000000 -0500
+++ linux-2.6.30.new/kernel/Makefile	2009-06-22 14:29:16.000000000 -0500
@@ -123,7 +123,7 @@
 $(obj)/time.o: $(obj)/timeconst.h
 
 quiet_cmd_timeconst  = TIMEC   $@
-      cmd_timeconst  = $(PERL) $< $(CONFIG_HZ) > $@
+      cmd_timeconst  = $(CONFIG_SHELL) $< $(CONFIG_HZ) $@
 targets += timeconst.h
-$(obj)/timeconst.h: $(src)/timeconst.pl FORCE
+$(obj)/timeconst.h: $(src)/timeconst.sh FORCE
 	$(call if_changed,timeconst)
diff -ruN linux-2.6.30/kernel/timeconst.pl linux-2.6.30.new/kernel/timeconst.pl
--- linux-2.6.30/kernel/timeconst.pl	2009-06-09 22:05:27.000000000 -0500
+++ linux-2.6.30.new/kernel/timeconst.pl	1969-12-31 18:00:00.000000000 -0600
@@ -1,378 +0,0 @@
-#!/usr/bin/perl
-# -----------------------------------------------------------------------
-#
-#   Copyright 2007-2008 rPath, Inc. - All Rights Reserved
-#
-#   This file is part of the Linux kernel, and is made available under
-#   the terms of the GNU General Public License version 2 or (at your
-#   option) any later version; incorporated herein by reference.
-#
-# -----------------------------------------------------------------------
-#
-
-#
-# Usage: timeconst.pl HZ > timeconst.h
-#
-
-# Precomputed values for systems without Math::BigInt
-# Generated by:
-# timeconst.pl --can 24 32 48 64 100 122 128 200 250 256 300 512 1000 1024 1200
-%canned_values = (
-	24 => [
-		'0xa6aaaaab','0x2aaaaaa',26,
-		125,3,
-		'0xc49ba5e4','0x1fbe76c8b4',37,
-		3,125,
-		'0xa2c2aaab','0xaaaa',16,
-		125000,3,
-		'0xc9539b89','0x7fffbce4217d',47,
-		3,125000,
-	], 32 => [
-		'0xfa000000','0x6000000',27,
-		125,4,
-		'0x83126e98','0xfdf3b645a',36,
-		4,125,
-		'0xf4240000','0x0',17,
-		31250,1,
-		'0x8637bd06','0x3fff79c842fa',46,
-		1,31250,
-	], 48 => [
-		'0xa6aaaaab','0x6aaaaaa',27,
-		125,6,
-		'0xc49ba5e4','0xfdf3b645a',36,
-		6,125,
-		'0xa2c2aaab','0x15555',17,
-		62500,3,
-		'0xc9539b89','0x3fffbce4217d',46,
-		3,62500,
-	], 64 => [
-		'0xfa000000','0xe000000',28,
-		125,8,
-		'0x83126e98','0x7ef9db22d',35,
-		8,125,
-		'0xf4240000','0x0',18,
-		15625,1,
-		'0x8637bd06','0x1fff79c842fa',45,
-		1,15625,
-	], 100 => [
-		'0xa0000000','0x0',28,
-		10,1,
-		'0xcccccccd','0x733333333',35,
-		1,10,
-		'0x9c400000','0x0',18,
-		10000,1,
-		'0xd1b71759','0x1fff2e48e8a7',45,
-		1,10000,
-	], 122 => [
-		'0x8325c53f','0xfbcda3a',28,
-		500,61,
-		'0xf9db22d1','0x7fbe76c8b',35,
-		61,500,
-		'0x8012e2a0','0x3ef36',18,
-		500000,61,
-		'0xffda4053','0x1ffffbce4217',45,
-		61,500000,
-	], 128 => [
-		'0xfa000000','0x1e000000',29,
-		125,16,
-		'0x83126e98','0x3f7ced916',34,
-		16,125,
-		'0xf4240000','0x40000',19,
-		15625,2,
-		'0x8637bd06','0xfffbce4217d',44,
-		2,15625,
-	], 200 => [
-		'0xa0000000','0x0',29,
-		5,1,
-		'0xcccccccd','0x333333333',34,
-		1,5,
-		'0x9c400000','0x0',19,
-		5000,1,
-		'0xd1b71759','0xfff2e48e8a7',44,
-		1,5000,
-	], 250 => [
-		'0x80000000','0x0',29,
-		4,1,
-		'0x80000000','0x180000000',33,
-		1,4,
-		'0xfa000000','0x0',20,
-		4000,1,
-		'0x83126e98','0x7ff7ced9168',43,
-		1,4000,
-	], 256 => [
-		'0xfa000000','0x3e000000',30,
-		125,32,
-		'0x83126e98','0x1fbe76c8b',33,
-		32,125,
-		'0xf4240000','0xc0000',20,
-		15625,4,
-		'0x8637bd06','0x7ffde7210be',43,
-		4,15625,
-	], 300 => [
-		'0xd5555556','0x2aaaaaaa',30,
-		10,3,
-		'0x9999999a','0x1cccccccc',33,
-		3,10,
-		'0xd0555556','0xaaaaa',20,
-		10000,3,
-		'0x9d495183','0x7ffcb923a29',43,
-		3,10000,
-	], 512 => [
-		'0xfa000000','0x7e000000',31,
-		125,64,
-		'0x83126e98','0xfdf3b645',32,
-		64,125,
-		'0xf4240000','0x1c0000',21,
-		15625,8,
-		'0x8637bd06','0x3ffef39085f',42,
-		8,15625,
-	], 1000 => [
-		'0x80000000','0x0',31,
-		1,1,
-		'0x80000000','0x0',31,
-		1,1,
-		'0xfa000000','0x0',22,
-		1000,1,
-		'0x83126e98','0x1ff7ced9168',41,
-		1,1000,
-	], 1024 => [
-		'0xfa000000','0xfe000000',32,
-		125,128,
-		'0x83126e98','0x7ef9db22',31,
-		128,125,
-		'0xf4240000','0x3c0000',22,
-		15625,16,
-		'0x8637bd06','0x1fff79c842f',41,
-		16,15625,
-	], 1200 => [
-		'0xd5555556','0xd5555555',32,
-		5,6,
-		'0x9999999a','0x66666666',31,
-		6,5,
-		'0xd0555556','0x2aaaaa',22,
-		2500,3,
-		'0x9d495183','0x1ffcb923a29',41,
-		3,2500,
-	]
-);
-
-$has_bigint = eval 'use Math::BigInt qw(bgcd); 1;';
-
-sub bint($)
-{
-	my($x) = @_;
-	return Math::BigInt->new($x);
-}
-
-#
-# Constants for division by reciprocal multiplication.
-# (bits, numerator, denominator)
-#
-sub fmul($$$)
-{
-	my ($b,$n,$d) = @_;
-
-	$n = bint($n);
-	$d = bint($d);
-
-	return scalar (($n << $b)+$d-bint(1))/$d;
-}
-
-sub fadj($$$)
-{
-	my($b,$n,$d) = @_;
-
-	$n = bint($n);
-	$d = bint($d);
-
-	$d = $d/bgcd($n, $d);
-	return scalar (($d-bint(1)) << $b)/$d;
-}
-
-sub fmuls($$$) {
-	my($b,$n,$d) = @_;
-	my($s,$m);
-	my($thres) = bint(1) << ($b-1);
-
-	$n = bint($n);
-	$d = bint($d);
-
-	for ($s = 0; 1; $s++) {
-		$m = fmul($s,$n,$d);
-		return $s if ($m >= $thres);
-	}
-	return 0;
-}
-
-# Generate a hex value if the result fits in 64 bits;
-# otherwise skip.
-sub bignum_hex($) {
-	my($x) = @_;
-	my $s = $x->as_hex();
-
-	return (length($s) > 18) ? undef : $s;
-}
-
-# Provides mul, adj, and shr factors for a specific
-# (bit, time, hz) combination
-sub muladj($$$) {
-	my($b, $t, $hz) = @_;
-	my $s = fmuls($b, $t, $hz);
-	my $m = fmul($s, $t, $hz);
-	my $a = fadj($s, $t, $hz);
-	return (bignum_hex($m), bignum_hex($a), $s);
-}
-
-# Provides numerator, denominator values
-sub numden($$) {
-	my($n, $d) = @_;
-	my $g = bgcd($n, $d);
-	return ($n/$g, $d/$g);
-}
-
-# All values for a specific (time, hz) combo
-sub conversions($$) {
-	my ($t, $hz) = @_;
-	my @val = ();
-
-	# HZ_TO_xx
-	push(@val, muladj(32, $t, $hz));
-	push(@val, numden($t, $hz));
-
-	# xx_TO_HZ
-	push(@val, muladj(32, $hz, $t));
-	push(@val, numden($hz, $t));
-
-	return @val;
-}
-
-sub compute_values($) {
-	my($hz) = @_;
-	my @val = ();
-	my $s, $m, $a, $g;
-
-	if (!$has_bigint) {
-		die "$0: HZ == $hz not canned and ".
-		    "Math::BigInt not available\n";
-	}
-
-	# MSEC conversions
-	push(@val, conversions(1000, $hz));
-
-	# USEC conversions
-	push(@val, conversions(1000000, $hz));
-
-	return @val;
-}
-
-sub outputval($$)
-{
-	my($name, $val) = @_;
-	my $csuf;
-
-	if (defined($val)) {
-	    if ($name !~ /SHR/) {
-		$val = "U64_C($val)";
-	    }
-	    printf "#define %-23s %s\n", $name.$csuf, $val.$csuf;
-	}
-}
-
-sub output($@)
-{
-	my($hz, @val) = @_;
-	my $pfx, $bit, $suf, $s, $m, $a;
-
-	print "/* Automatically generated by kernel/timeconst.pl */\n";
-	print "/* Conversion constants for HZ == $hz */\n";
-	print "\n";
-	print "#ifndef KERNEL_TIMECONST_H\n";
-	print "#define KERNEL_TIMECONST_H\n";
-	print "\n";
-
-	print "#include <linux/param.h>\n";
-	print "#include <linux/types.h>\n";
-
-	print "\n";
-	print "#if HZ != $hz\n";
-	print "#error \"kernel/timeconst.h has the wrong HZ value!\"\n";
-	print "#endif\n";
-	print "\n";
-
-	foreach $pfx ('HZ_TO_MSEC','MSEC_TO_HZ',
-		      'HZ_TO_USEC','USEC_TO_HZ') {
-		foreach $bit (32) {
-			foreach $suf ('MUL', 'ADJ', 'SHR') {
-				outputval("${pfx}_$suf$bit", shift(@val));
-			}
-		}
-		foreach $suf ('NUM', 'DEN') {
-			outputval("${pfx}_$suf", shift(@val));
-		}
-	}
-
-	print "\n";
-	print "#endif /* KERNEL_TIMECONST_H */\n";
-}
-
-# Pretty-print Perl values
-sub perlvals(@) {
-	my $v;
-	my @l = ();
-
-	foreach $v (@_) {
-		if (!defined($v)) {
-			push(@l, 'undef');
-		} elsif ($v =~ /^0x/) {
-			push(@l, "\'".$v."\'");
-		} else {
-			push(@l, $v.'');
-		}
-	}
-	return join(',', @l);
-}
-
-($hz) = @ARGV;
-
-# Use this to generate the %canned_values structure
-if ($hz eq '--can') {
-	shift(@ARGV);
-	@hzlist = sort {$a <=> $b} (@ARGV);
-
-	print "# Precomputed values for systems without Math::BigInt\n";
-	print "# Generated by:\n";
-	print "# timeconst.pl --can ", join(' ', @hzlist), "\n";
-	print "\%canned_values = (\n";
-	my $pf = "\t";
-	foreach $hz (@hzlist) {
-		my @values = compute_values($hz);
-		print "$pf$hz => [\n";
-		while (scalar(@values)) {
-			my $bit;
-			foreach $bit (32) {
-				my $m = shift(@values);
-				my $a = shift(@values);
-				my $s = shift(@values);
-				print "\t\t", perlvals($m,$a,$s), ",\n";
-			}
-			my $n = shift(@values);
-			my $d = shift(@values);
-			print "\t\t", perlvals($n,$d), ",\n";
-		}
-		print "\t]";
-		$pf = ', ';
-	}
-	print "\n);\n";
-} else {
-	$hz += 0;			# Force to number
-	if ($hz < 1) {
-		die "Usage: $0 HZ\n";
-	}
-
-	@val = @{$canned_values{$hz}};
-	if (!defined(@val)) {
-		@val = compute_values($hz);
-	}
-	output($hz, @val);
-}
-exit 0;
diff -ruN linux-2.6.30/kernel/timeconst.sh linux-2.6.30.new/kernel/timeconst.sh
--- linux-2.6.30/kernel/timeconst.sh	1969-12-31 18:00:00.000000000 -0600
+++ linux-2.6.30.new/kernel/timeconst.sh	2009-06-22 14:29:16.000000000 -0500
@@ -0,0 +1,148 @@
+#!/bin/sh
+
+if [ $# -ne 2 ]
+then
+	echo "Usage: timeconst.sh HZ FILENAME"
+	echo
+	echo "Generate a header file with constants for coverting between"
+	echo "decimal HZ timer ticks and milisecond or microsecond delays."
+	echo
+	exit 1
+fi
+
+HZ=$1
+shift
+FILENAME=$1
+
+# Sanity test: even the shell in Red Hat 9 (circa 2003) supported 64 bit math.
+
+if [ $((1 << 32)) -lt 0 ]
+then
+	echo "timeconst.sh needs a shell with 64 bit math, such as bash,"
+	echo "busybox ash, or dash running on a 64 bit host."
+	exit 1
+fi
+
+# If this script exits for any reason before this trap is removed,
+# delete the output file so a partial file won't confuse the build.
+
+trap "rm $FILENAME" EXIT
+
+# Output start of header file
+
+cat > $FILENAME << EOF || exit 1
+/* Automatically generated by kernel/timeconst.sh */
+/* Conversion constants for HZ == $HZ */
+
+#ifndef __KERNEL_TIMECONST_H
+#define __KERNEL_TIMECONST_H
+
+#include <linux/param.h>
+#include <linux/types.h>
+
+#if HZ != $HZ
+#error "kernel/timeconst.h has the wrong HZ value!"
+#endif
+
+EOF
+
+# For both Milliseconds and Microseconds
+
+cat << EOF |
+MSEC 1000
+USEC 1000000
+EOF
+while read NAME PERIOD
+do
+	# Find greatest common denominator (using Euclid's algorithm)
+
+	A=$HZ
+	B=$PERIOD
+
+	while [ $B -ne 0 ]
+	do
+		C=$(( $A % $B ))
+		A=$B
+		B=$C
+	done
+
+	GCD=$A
+
+	# Do this for each direction (HZ_TO_PERIOD and PERIOD_TO_HZ)
+
+	for DIRECTION in 0 1
+	do
+		if [ $DIRECTION -eq 0 ]
+		then
+			CONVERT="HZ_TO_${NAME}"
+			FROM=$HZ
+			TO=$PERIOD
+		else
+			CONVERT="${NAME}_TO_HZ"
+			FROM=$PERIOD
+			TO=$HZ
+		fi
+
+		# Calculate 32 significant bits of MUL32 data.
+
+		SHIFT=0
+		while true
+		do
+			# This can't overflow 64 bit math.  Pathological case
+			# (TO=1, FROM=1000000) uses around 32+20=52 bits.
+
+			MUL32=$(( ( ( $TO << $SHIFT ) + $FROM - 1 ) / $FROM ))
+
+			# Keep increasing $SHIFT until we've got 32 bits.
+
+			[ $MUL32 -gt $(( 1 << 31 )) ] && break
+			SHIFT=$(( $SHIFT + 1 ))
+		done
+		MUL32=$( printf %x $MUL32 )
+
+		# ADJ32 is just (((FROM/GCD)-1)<<SHIFT)/(FROM/GCD) but this
+		# can overflow 64 bit math (examples, HZ=24 or HZ=122).
+		# Pathological case could use 32+20+20=72 bits.  (And this is
+		# the pathological case because a larger $HZ results in a
+		# smaller $SHIFT, so even insane HZ>USEC cases should be ok.)
+
+		# To get around this, we chop the bottom 32 bits off the
+		# calculation and then reassemble it to avoid overflow:
+		# 32+64=96, which is > 72.
+
+		ADJ32=$(( $FROM / $GCD ))
+		if [ $SHIFT -gt 32 ]
+		then
+			UPPER=$(( ( $ADJ32 - 1 ) << ( $SHIFT - 32 ) ))
+			LOWER=$(( ( $UPPER % $ADJ32 ) << 32 ))
+			ADJ32=$(( ( ( $UPPER / $ADJ32 ) << 32 ) + ( $LOWER / $ADJ32 )))
+		else
+			ADJ32=$(( ( ( $ADJ32 - 1 ) << $SHIFT) / $ADJ32 ))
+		fi
+		ADJ32=$( printf %x $ADJ32 )
+
+		NUM=$(( $TO / $GCD ))
+		DEN=$(( $FROM / $GCD ))
+
+		# Output next chunk of header data to file
+
+		(
+			echo "#define ${CONVERT}_MUL32	U64_C(0x$MUL32)" &&
+			echo "#define ${CONVERT}_ADJ32	U64_C(0x$ADJ32)" &&
+			echo "#define ${CONVERT}_SHR32	$SHIFT" &&
+			echo "#define ${CONVERT}_NUM		U64_C($NUM)" &&
+			echo "#define ${CONVERT}_DEN		U64_C($DEN)"
+		) >> $FILENAME || exit 1
+	done
+done
+
+(
+	echo
+	echo "#endif /* __KERNEL_TIMECHONST_H */"
+) >> $FILENAME || exit 1
+
+# Don't rm $FILENAME on exit anymore.
+
+trap "" EXIT
+
+exit 0

-- 
Latency is more important than throughput. It's that simple. - Linus Torvalds
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