linux-kernel - [PATCH] rcutorture: Select from only online CPUs

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Message-Id: <20190323034619.15792-1-joel@joelfernandes.org>
Date:   Fri, 22 Mar 2019 23:46:19 -0400
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Josh Triplett <josh@...htriplett.org>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kselftest@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Shuah Khan <shuah@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>
Subject: [PATCH] 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.

Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.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