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

   1 #!/bin/bash
   2 # SPDX-License-Identifier: GPL-2.0+
   3 #
   4 # Alternate sleeping and spinning on randomly selected CPUs.  The purpose
   5 # of this script is to inflict random OS jitter on a concurrently running
   6 # test.
   7 #
   8 # Usage: jitter.sh me duration [ sleepmax [ spinmax ] ]
   9 #
  10 # me: Random-number-generator seed salt.
  11 # duration: Time to run in seconds.
  12 # sleepmax: Maximum microseconds to sleep, defaults to one second.
  13 # spinmax: Maximum microseconds to spin, defaults to one millisecond.
  14 #
  15 # Copyright (C) IBM Corporation, 2016
  16 #
  17 # Authors: Paul E. McKenney <paulmck@linux.ibm.com>
  18
  19 me=$(($1 * 1000))
  20 duration=$2
  21 sleepmax=${3-1000000}
  22 spinmax=${4-1000}
  23
  24 n=1
  25
  26 starttime=`awk 'BEGIN { print systime(); }' < /dev/null`
  27
  28 while :
  29 do
  30         # Check for done.
  31         t=`awk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
  32         if test "$t" -gt "$duration"
  33         then
  34                 exit 0;
  35         fi
  36
  37         # Set affinity to randomly selected online CPU
  38         cpus=`grep 1 /sys/devices/system/cpu/*/online |
  39                 sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
  40
  41         # Do not leave out poor old cpu0 which may not be hot-pluggable
  42         if [ ! -f "/sys/devices/system/cpu/cpu0/online" ]; then
  43                 cpus="0 $cpus"
  44         fi
  45
  46         cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
  47                 srand(n + me + systime());
  48                 ncpus = split(cpus, ca);
  49                 curcpu = ca[int(rand() * ncpus + 1)];
  50                 mask = lshift(1, curcpu);
  51                 if (mask + 0 <= 0)
  52                         mask = 1;
  53                 printf("%#x\n", mask);
  54         }' < /dev/null`
  55         n=$(($n+1))
  56         if ! taskset -p $cpumask $$ > /dev/null 2>&1
  57         then
  58                 echo taskset failure: '"taskset -p ' $cpumask $$ '"'
  59                 exit 1
  60         fi
  61
  62         # Sleep a random duration
  63         sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
  64                 srand(n + me + systime());
  65                 printf("%06d", int(rand() * sleepmax));
  66         }' < /dev/null`
  67         n=$(($n+1))
  68         sleep .$sleeptime
  69
  70         # Spin a random duration
  71         limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
  72                 srand(n + me + systime());
  73                 printf("%06d", int(rand() * spinmax));
  74         }' < /dev/null`
  75         n=$(($n+1))
  76         for i in {1..$limit}
  77         do
  78                 echo > /dev/null
  79         done
  80 done
  81
  82 exit 1