rcutorture: Select from only online CPUs

The rcutorture jitter.sh script selects a random CPU but does not check
if it is offline or online. This leads to taskset errors many times. On
my machine, hyper threading is disabled so half the cores are offline
causing taskset errors a lot of times. Let us fix this by checking from
only the online CPUs on the system.

Cc: rcu@vger.kernel.org
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
index 435b609339854fddfce767c5aa8e93c6fc31e3bb..81c6e6ab5d830acce38dcee52c96ab71f277f87d 100755 (executable)
--- a/tools/testing/selftests/rcutorture/bin/jitter.sh
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -34,10 +34,11 @@ do
                exit 0;
        fi
 
-       # Set affinity to randomly selected CPU
-       cpus=`ls /sys/devices/system/cpu/*/online |
+       # Set affinity to randomly selected online CPU
+       cpus=`grep 1 /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);