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=`gawk 'BEGIN { print systime(); }' < /dev/null`
  27
  28 nohotplugcpus=
  29 for i in /sys/devices/system/cpu/cpu[0-9]*
  30 do
  31         if test -f $i/online
  32         then
  33                 :
  34         else
  35                 curcpu=`echo $i | sed -e 's/^[^0-9]*//'`
  36                 nohotplugcpus="$nohotplugcpus $curcpu"
  37         fi
  38 done
  39
  40 while :
  41 do
  42         # Check for done.
  43         t=`gawk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
  44         if test "$t" -gt "$duration"
  45         then
  46                 exit 0;
  47         fi
  48
  49         # Set affinity to randomly selected online CPU
  50         if cpus=`grep 1 /sys/devices/system/cpu/*/online 2>&1 |
  51                  sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
  52         then
  53                 :
  54         else
  55                 cpus=
  56         fi
  57         # Do not leave out non-hot-pluggable CPUs
  58         cpus="$cpus $nohotplugcpus"
  59
  60         cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
  61                 srand(n + me + systime());
  62                 ncpus = split(cpus, ca);
  63                 curcpu = ca[int(rand() * ncpus + 1)];
  64                 mask = lshift(1, curcpu);
  65                 if (mask + 0 <= 0)
  66                         mask = 1;
  67                 printf("%#x\n", mask);
  68         }' < /dev/null`
  69         n=$(($n+1))
  70         if ! taskset -p $cpumask $$ > /dev/null 2>&1
  71         then
  72                 echo taskset failure: '"taskset -p ' $cpumask $$ '"'
  73                 exit 1
  74         fi
  75
  76         # Sleep a random duration
  77         sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
  78                 srand(n + me + systime());
  79                 printf("%06d", int(rand() * sleepmax));
  80         }' < /dev/null`
  81         n=$(($n+1))
  82         sleep .$sleeptime
  83
  84         # Spin a random duration
  85         limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
  86                 srand(n + me + systime());
  87                 printf("%06d", int(rand() * spinmax));
  88         }' < /dev/null`
  89         n=$(($n+1))
  90         for i in {1..$limit}
  91         do
  92                 echo > /dev/null
  93         done
  94 done
  95
  96 exit 1