linux-kernel - [PATCH v2 3/4] rcutorture: Select from only online CPUs

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Date:   Tue, 26 Mar 2019 15:24:10 -0400
From:   "Joel Fernandes (Google)" <joel@...lfernandes.org>
To:     linux-kernel@...r.kernel.org
Cc:     "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        rcu@...r.kernel.org, byungchul.park@....com,
        Ingo Molnar <mingo@...hat.com>,
        Josh Triplett <josh@...htriplett.org>, kernel-team@...roid.com,
        Lai Jiangshan <jiangshanlai@...il.com>,
        linux-kselftest@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        "Paul E. McKenney" <paulmck@...ux.ibm.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Shuah Khan <shuah@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Will Deacon <will.deacon@....com>
Subject: [PATCH v2 3/4] 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@...r.kernel.org
Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
---
 tools/testing/selftests/rcutorture/bin/jitter.sh | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
index 3633828375e3..47bd9829dc55 100755
--- a/tools/testing/selftests/rcutorture/bin/jitter.sh
+++ b/tools/testing/selftests/rcutorture/bin/jitter.sh
@@ -47,10 +47,11 @@ 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);
-- 
2.21.0.392.gf8f6787159e-goog