tools/testing/selftests/rcutorture/bin/jitter.sh

   1 #!/bin/bash
   2 #
   3 # Alternate sleeping and spinning on randomly selected CPUs.  The purpose
   4 # of this script is to inflict random OS jitter on a concurrently running
   5 # test.
   6 #
   7 # Usage: jitter.sh me duration [ sleepmax [ spinmax ] ]
   8 #
   9 # me: Random-number-generator seed salt.
  10 # duration: Time to run in seconds.
  11 # sleepmax: Maximum microseconds to sleep, defaults to one second.
  12 # spinmax: Maximum microseconds to spin, defaults to one millisecond.
  13 #
  14 # This program is free software; you can redistribute it and/or modify
  15 # it under the terms of the GNU General Public License as published by
  16 # the Free Software Foundation; either version 2 of the License, or
  17 # (at your option) any later version.
  18 #
  19 # This program is distributed in the hope that it will be useful,
  20 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  21 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  22 # GNU General Public License for more details.
  23 #
  24 # You should have received a copy of the GNU General Public License
  25 # along with this program; if not, you can access it online at
  26 # http://www.gnu.org/licenses/gpl-2.0.html.
  27 #
  28 # Copyright (C) IBM Corporation, 2016
  29 #
  30 # Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
  31
  32 me=$(($1 * 1000))
  33 duration=$2
  34 sleepmax=${3-1000000}
  35 spinmax=${4-1000}
  36
  37 n=1
  38
  39 starttime=`awk 'BEGIN { print systime(); }' < /dev/null`
  40
  41 while :
  42 do
  43         # Check for done.
  44         t=`awk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
  45         if test "$t" -gt "$duration"
  46         then
  47                 exit 0;
  48         fi
  49
  50         # Set affinity to randomly selected CPU
  51         cpus=`ls /sys/devices/system/cpu/*/online |
  52                 sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
  53                 grep -v '^0*$'`
  54         cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
  55                 srand(n + me + systime());
  56                 ncpus = split(cpus, ca);
  57                 curcpu = ca[int(rand() * ncpus + 1)];
  58                 mask = lshift(1, curcpu);
  59                 if (mask + 0 <= 0)
  60                         mask = 1;
  61                 printf("%#x\n", mask);
  62         }' < /dev/null`
  63         n=$(($n+1))
  64         if ! taskset -p $cpumask $$ > /dev/null 2>&1
  65         then
  66                 echo taskset failure: '"taskset -p ' $cpumask $$ '"'
  67                 exit 1
  68         fi
  69
  70         # Sleep a random duration
  71         sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
  72                 srand(n + me + systime());
  73                 printf("%06d", int(rand() * sleepmax));
  74         }' < /dev/null`
  75         n=$(($n+1))
  76         sleep .$sleeptime
  77
  78         # Spin a random duration
  79         limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
  80                 srand(n + me + systime());
  81                 printf("%06d", int(rand() * spinmax));
  82         }' < /dev/null`
  83         n=$(($n+1))
  84         for i in {1..$limit}
  85         do
  86                 echo > /dev/null
  87         done
  88 done
  89
  90 exit 1