[PATCH] rcutorture: Select from only online CPUs

["Joel Fernandes (Google)" <joel@joelfernandes.org>]

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.

Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
 tools/testing/selftests/rcutorture/bin/jitter.sh | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
index 3633828375e3..53bf9d99b5cd 100755
--- a/tools/testing/selftests/rcutorture/bin/jitter.sh
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -47,10 +47,19 @@ do
 		exit 0;
 	fi
 
-	# Set affinity to randomly selected CPU
+	# Set affinity to randomly selected online CPU
 	cpus=`ls /sys/devices/system/cpu/*/online |
 		sed -e 's,/[^/]*$,,' -e 's/^[^0-9]*//' |
 		grep -v '^0*$'`
+
+	for c in $cpus; do
+		if [ "$(cat /sys/devices/system/cpu/cpu$c/online)" == "1" ];
+		then
+			cpus_tmp="$cpus_tmp $c"
+		fi
+	done
+	cpus=$cpus_tmp
+
 	cpumask=`awk -v cpus="$cpus" -v me=$me -v n=$n 'BEGIN {
 		srand(n + me + systime());
 		ncpus = split(cpus, ca);
-- 
2.21.0.392.gf8f6787159e-goog