torture: Handle jitter for CPUs that cannot be offlined

Currently, jitter.sh assumes that the underlying hypervisor will be
configured with all CPUs hotpluggable, with the possible exception
of CPU 0.  However, there are installations where the hypervisor
prohibits offlining, which breaks jitter.sh.  This commit therefore
lists the CPUs that cannot be offlined up front, and checks for the
case where no CPU can be offlined in the loop.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
index 86a217b41b9f11be550891bcc8da07fadebd1494..30cb5b27d32e56cb629b36a911d8bda029db2def 100755 (executable)
--- a/tools/testing/selftests/rcutorture/bin/jitter.sh
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -25,6 +25,18 @@ n=1
 
 starttime=`gawk 'BEGIN { print systime(); }' < /dev/null`
 
+nohotplugcpus=
+for i in /sys/devices/system/cpu/cpu[0-9]*
+do
+       if test -f $i/online
+       then
+               :
+       else
+               curcpu=`echo $i | sed -e 's/^[^0-9]*//'`
+               nohotplugcpus="$nohotplugcpus $curcpu"
+       fi
+done
+
 while :
 do
        # Check for done.
@@ -35,13 +47,15 @@ do
        fi
 
        # Set affinity to randomly selected online CPU
-       cpus=`grep 1 /sys/devices/system/cpu/*/online |
-               sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
-
-       # Do not leave out poor old cpu0 which may not be hot-pluggable
-       if [ ! -f "/sys/devices/system/cpu/cpu0/online" ]; then
-               cpus="0 $cpus"
+       if cpus=`grep 1 /sys/devices/system/cpu/*/online 2>&1 |
+                sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//'`
+       then
+               :
+       else
+               cpus=
        fi
+       # Do not leave out non-hot-pluggable CPUs
+       cpus="$cpus $nohotplugcpus"
 
        cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
                srand(n + me + systime());