rcutorture: Add OS-jitter capability

This commit adds a --jitter OS-jitter capability to expose bugs based
on no-delay assumptions.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

2 files changed, 108 insertions, 0 deletions

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
new file mode 100755
index 000000000000..3633828375e3
--- /dev/null
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -0,0 +1,90 @@
+#!/bin/bash
+#
+# Alternate sleeping and spinning on randomly selected CPUs.  The purpose
+# of this script is to inflict random OS jitter on a concurrently running
+# test.
+#
+# Usage: jitter.sh me duration [ sleepmax [ spinmax ] ]
+#
+# me: Random-number-generator seed salt.
+# duration: Time to run in seconds.
+# sleepmax: Maximum microseconds to sleep, defaults to one second.
+# spinmax: Maximum microseconds to spin, defaults to one millisecond.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, you can access it online at
+# http://www.gnu.org/licenses/gpl-2.0.html.
+#
+# Copyright (C) IBM Corporation, 2016
+#
+# Authors: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
+
+me=$(($1 * 1000))
+duration=$2
+sleepmax=${3-1000000}
+spinmax=${4-1000}
+
+n=1
+
+starttime=`awk 'BEGIN { print systime(); }' < /dev/null`
+
+while :
+do
+        # Check for done.
+        t=`awk -v s=$starttime 'BEGIN { print systime() - s; }' < /dev/null`
+        if test "$t" -gt "$duration"
+        then
+                exit 0;
+        fi
+
+        # Set affinity to randomly selected CPU
+        cpus=`ls /sys/devices/system/cpu/*/online |
+                sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
+                grep -v '^0*$'`
+        cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
+                srand(n + me + systime());
+                ncpus = split(cpus, ca);
+                curcpu = ca[int(rand() * ncpus + 1)];
+                mask = lshift(1, curcpu);
+                if (mask + 0 <= 0)
+                        mask = 1;
+                printf("%#x\n", mask);
+        }' < /dev/null`
+        n=$(($n+1))
+        if ! taskset -p $cpumask $$ > /dev/null 2>&1
+        then
+                echo taskset failure: '"taskset -p ' $cpumask $$ '"'
+                exit 1
+        fi
+
+        # Sleep a random duration
+        sleeptime=`awk -v me=$me -v n=$n -v sleepmax=$sleepmax 'BEGIN {
+                srand(n + me + systime());
+                printf("%06d", int(rand() * sleepmax));
+        }' < /dev/null`
+        n=$(($n+1))
+        sleep .$sleeptime
+
+        # Spin a random duration
+        limit=`awk -v me=$me -v n=$n -v spinmax=$spinmax 'BEGIN {
+                srand(n + me + systime());
+                printf("%06d", int(rand() * spinmax));
+        }' < /dev/null`
+        n=$(($n+1))
+        for i in {1..$limit}
+        do
+                echo > /dev/null
+        done
+done
+
+exit 1
diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh
index 704e219f67a7..0d598145873e 100755
--- a/tools/testing/selftests/rcutorture/bin/kvm.sh
+++ b/tools/testing/selftests/rcutorture/bin/kvm.sh
@@ -48,6 +48,7 @@ resdir=""
 configs=""
 cpus=0
 ds=`date +%Y.%m.%d-%H:%M:%S`
+jitter=0
 
 . functions.sh
 
@@ -63,6 +64,7 @@ usage () {
         echo "       --dryrun sched|script"
         echo "       --duration minutes"
         echo "       --interactive"
+        echo "       --jitter N [ maxsleep (us) [ maxspin (us) ] ]"
         echo "       --kmake-arg kernel-make-arguments"
         echo "       --mac nn:nn:nn:nn:nn:nn"
         echo "       --no-initrd"
@@ -122,6 +124,11 @@ do
         --interactive)
                 TORTURE_QEMU_INTERACTIVE=1; export TORTURE_QEMU_INTERACTIVE
                 ;;
+        --jitter)
+                checkarg --jitter "(# threads [ sleep [ spin ] ])" $# "$2" '^-\{,1\}[0-9]\+\( \+[0-9]\+\)\{,2\} *$' '^error$'
+                jitter="$2"
+                shift
+                ;;
         --kmake-arg)
                 checkarg --kmake-arg "(kernel make arguments)" $# "$2" '.*' '^error$'
                 TORTURE_KMAKE_ARG="$2"
@@ -299,6 +306,7 @@ awk < $T/cfgcpu.pack \
         -v CONFIGDIR="$CONFIGFRAG/" \
         -v KVM="$KVM" \
         -v ncpus=$cpus \
+        -v jitter="$jitter" \
         -v rd=$resdir/$ds/ \
         -v dur=$dur \
         -v TORTURE_QEMU_ARG="$TORTURE_QEMU_ARG" \
@@ -359,6 +367,16 @@ function dump(first, pastlast, batchnum)
                 print "\techo ----", cfr[j], cpusr[j] ovf ": Starting kernel. `date` >> " rd "/log";
                 print "fi"
         }
+        njitter = 0;
+        split(jitter, ja);
+        if (ja[1] == -1 && ncpus == 0)
+                njitter = 1;
+        else if (ja[1] == -1)
+                njitter = ncpus;
+        else
+                njitter = ja[1];
+        for (j = 0; j < njitter; j++)
+                print "jitter.sh " j " " dur " " ja[2] " " ja[3] "&"
         print "wait"
         print "if test -z \"$TORTURE_BUILDONLY\""
         print "then"