linux-kernel - [PATCH tip/core/rcu 03/12] torture: Handle jitter for CPUs that cannot be offlined

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Message-Id: <20191210034217.405-3-paulmck@kernel.org>
Date:   Mon,  9 Dec 2019 19:42:08 -0800
From:   paulmck@...nel.org
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [PATCH tip/core/rcu 03/12] torture: Handle jitter for CPUs that cannot be offlined

From: "Paul E. McKenney" <paulmck@...nel.org>

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@...nel.org>
---
 tools/testing/selftests/rcutorture/bin/jitter.sh | 26 ++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/rcutorture/bin/jitter.sh b/tools/testing/selftests/rcutorture/bin/jitter.sh
index 86a217b..30cb5b2 100755
--- 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());
-- 
2.9.5