tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
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
19me=$(($1 * 1000))
20duration=$2
21sleepmax=${3-1000000}
22spinmax=${4-1000}
23
24n=1
25
26starttime=`gawk 'BEGIN { print systime(); }' < /dev/null`
27
28nohotplugcpus=
29for i in /sys/devices/system/cpu/cpu[0-9]*
30do
31 if test -f $i/online
32 then
33 :
34 else
35 curcpu=`echo $i | sed -e 's/^[^0-9]*//'`
36 nohotplugcpus="$nohotplugcpus $curcpu"
37 fi
38done
39
40while :
41do
42 # Check for done.
43 t=`gawk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
44 if test "$t" -gt "$duration"
45 then
46 exit 0;
47 fi
48
49 # Check for stop request.
50 if test -f "$TORTURE_STOPFILE"
51 then
52 exit 1;
53 fi
54
55 # Set affinity to randomly selected online CPU
56 if cpus=`grep 1 /sys/devices/system/cpu/*/online 2>&1 |
57 sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
58 then
59 :
60 else
61 cpus=
62 fi
63 # Do not leave out non-hot-pluggable CPUs
64 cpus="$cpus $nohotplugcpus"
65
66 cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
67 srand(n + me + systime());
68 ncpus = split(cpus, ca);
69 curcpu = ca[int(rand() * ncpus + 1)];
70 mask = lshift(1, curcpu);
71 if (mask + 0 <= 0)
72 mask = 1;
73 printf("%#x\n", mask);
74 }' < /dev/null`
75 n=$(($n+1))
76 if ! taskset -p $cpumask $$ > /dev/null 2>&1
77 then
78 echo taskset failure: '"taskset -p ' $cpumask $$ '"'
79 exit 1
80 fi
81
82 # Sleep a random duration
83 sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
84 srand(n + me + systime());
85 printf("%06d", int(rand() * sleepmax));
86 }' < /dev/null`
87 n=$(($n+1))
88 sleep .$sleeptime
89
90 # Spin a random duration
91 limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
92 srand(n + me + systime());
93 printf("%06d", int(rand() * spinmax));
94 }' < /dev/null`
95 n=$(($n+1))
96 for i in {1..$limit}
97 do
98 echo > /dev/null
99 done
100done
101
102exit 1