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 jittering-path duration [ sleepmax [ spinmax ] ]
   9 #
  10 # me: Random-number-generator seed salt.
  11 # duration: Time to run in seconds.
  12 # jittering-path: Path to file whose removal will stop this script.
  13 # sleepmax: Maximum microseconds to sleep, defaults to one second.
  14 # spinmax: Maximum microseconds to spin, defaults to one millisecond.
  15 #
  16 # Copyright (C) IBM Corporation, 2016
  17 #
  18 # Authors: Paul E. McKenney <paulmck@linux.ibm.com>
  19
  20 me=$(($1 * 1000))
  21 jittering=$2
  22 duration=$3
  23 sleepmax=${4-1000000}
  24 spinmax=${5-1000}
  25
  26 n=1
  27
  28 starttime=`gawk 'BEGIN { print systime(); }' < /dev/null`
  29
  30 nohotplugcpus=
  31 for i in /sys/devices/system/cpu/cpu[0-9]*
  32 do
  33         if test -f $i/online
  34         then
  35                 :
  36         else
  37                 curcpu=`echo $i | sed -e 's/^[^0-9]*//'`
  38                 nohotplugcpus="$nohotplugcpus $curcpu"
  39         fi
  40 done
  41
  42 while :
  43 do
  44         # Check for done.
  45         t=`gawk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
  46         if test "$t" -gt "$duration"
  47         then
  48                 exit 0;
  49         fi
  50
  51         # Check for stop request.
  52         if ! test -f "$jittering"
  53         then
  54                 exit 1;
  55         fi
  56
  57         # Set affinity to randomly selected online CPU
  58         if cpus=`grep 1 /sys/devices/system/cpu/*/online 2>&1 |
  59                  sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
  60         then
  61                 :
  62         else
  63                 cpus=
  64         fi
  65         # Do not leave out non-hot-pluggable CPUs
  66         cpus="$cpus $nohotplugcpus"
  67
  68         cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
  69                 srand(n + me + systime());
  70                 ncpus = split(cpus, ca);
  71                 print ca[int(rand() * ncpus + 1)];
  72         }' < /dev/null`
  73         n=$(($n+1))
  74         if ! taskset -c -p $cpumask $$ > /dev/null 2>&1
  75         then
  76                 echo taskset failure: '"taskset -c -p ' $cpumask $$ '"'
  77                 exit 1
  78         fi
  79
  80         # Sleep a random duration
  81         sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
  82                 srand(n + me + systime());
  83                 printf("%06d", int(rand() * sleepmax));
  84         }' < /dev/null`
  85         n=$(($n+1))
  86         sleep .$sleeptime
  87
  88         # Spin a random duration
  89         limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
  90                 srand(n + me + systime());
  91                 printf("%06d", int(rand() * spinmax));
  92         }' < /dev/null`
  93         n=$(($n+1))
  94         for i in {1..$limit}
  95         do
  96                 echo > /dev/null
  97         done
  98 done
  99
 100 exit 1