#!/bin/bash
#
# Alternate sleeping and spinning on randomly selected CPUs.  The purpose
# of this script is to inflict random OS jitter on a concurrently running
# test.
#
# Usage: jitter.sh me duration [ sleepmax [ spinmax ] ]
#
# me: Random-number-generator seed salt.
# duration: Time to run in seconds.
# sleepmax: Maximum microseconds to sleep, defaults to one second.
# spinmax: Maximum microseconds to spin, defaults to one millisecond.
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, you can access it online at
# http://www.gnu.org/licenses/gpl-2.0.html.
#
# Copyright (C) IBM Corporation, 2016
#
# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

me=$(($1 * 1000))
duration=$2
sleepmax=${3-1000000}
spinmax=${4-1000}

n=1

starttime=`awk 'BEGIN { print systime(); }' < /dev/null`

while :
do
	# Check for done.
	t=`awk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
	if test "$t" -gt "$duration"
	then
		exit 0;
	fi

	# Set affinity to randomly selected CPU
	cpus=`ls /sys/devices/system/cpu/*/online |
		sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
		grep -v '^0*$'`
	cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
		srand(n + me + systime());
		ncpus = split(cpus, ca);
		curcpu = ca[int(rand() * ncpus + 1)];
		mask = lshift(1, curcpu);
		if (mask + 0 <= 0)
			mask = 1;
		printf("%#x\n", mask);
	}' < /dev/null`
	n=$(($n+1))
	if ! taskset -p $cpumask $$ > /dev/null 2>&1
	then
		echo taskset failure: '"taskset -p ' $cpumask $$ '"'
		exit 1
	fi

	# Sleep a random duration
	sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
		srand(n + me + systime());
		printf("%06d", int(rand() * sleepmax));
	}' < /dev/null`
	n=$(($n+1))
	sleep .$sleeptime

	# Spin a random duration
	limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
		srand(n + me + systime());
		printf("%06d", int(rand() * spinmax));
	}' < /dev/null`
	n=$(($n+1))
	for i in {1..$limit}
	do
		echo > /dev/null
	done
done

exit 1
value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/cgit.cgi/linux/net-next.git/diff/?id=23fbe2cdc1de80120cf9ccd478ac57c3a3a0764b&amp;id2=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>root</a>/<a href='/cgit.cgi/linux/net-next.git/diff/net?id=23fbe2cdc1de80120cf9ccd478ac57c3a3a0764b&amp;id2=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>net</a>/<a href='/cgit.cgi/linux/net-next.git/diff/net/sctp?id=23fbe2cdc1de80120cf9ccd478ac57c3a3a0764b&amp;id2=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>sctp</a>/<a href='/cgit.cgi/linux/net-next.git/diff/net/sctp/auth.c?id=23fbe2cdc1de80120cf9ccd478ac57c3a3a0764b&amp;id2=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>auth.c</a></div><div class='content'><div class='cgit-panel'><b>diff options</b><form method='get'><input type='hidden' name='id' value='23fbe2cdc1de80120cf9ccd478ac57c3a3a0764b'/><input type='hidden' name='id2' value='926af6273fc683cd98cd0ce7bf0d04a02eed6742'/><table><tr><td colspan='2'/></tr><tr><td class='label'>context:</td><td class='ctrl'><select name='context' onchange='this.form.submit();'><option value='1'>1</option><option value='2'>2</option><option value='3' selected='selected'>3</option><option value='4'>4</option><option value='5'>5</option><option value='6'>6</option><option value='7'>7</option><option value='8'>8</option><option value='9'>9</option><option value='10'>10</option><option value='15'>15</option><option value='20'>20</option><option value='25'>25</option><option value='30'>30</option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=23fbe2cdc1de80120cf9ccd478ac57c3a3a0764b&amp;id2=926af6273fc683cd98cd0ce7bf0d04a02eed6742'>Diffstat</a> (limited to 'net/sctp/auth.c')</div><table summary='diffstat' class='diffstat'>