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Date:   Thu, 10 Jan 2019 11:37:25 +0000
From:   Colin King <>
To:     Shuah Khan <>,
Subject: [PATCH] selftests: cpu-hotplug: fix case where CPUs offline > CPUs present

From: Colin Ian King <>

The cpu-hotplug test assumes that we can offline the maximum CPU as
described by /sys/devices/system/cpu/offline.  However, in the case
where the number of CPUs exceeds like kernel configuration then
the offline count can be greater than the present count and we end
up trying to test the offlining of a CPU that is not available to
offline.  Fix this by testing the maximum present CPU instead.

Also, the test currently offlines the CPU and does not online it,
so fix this by onlining the CPU after the test.

Fixes: d89dffa976bc ("fault-injection: add selftests for cpu and memory hotplug")
Signed-off-by: Colin Ian King <>
 .../selftests/cpu-hotplug/      | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/cpu-hotplug/ b/tools/testing/selftests/cpu-hotplug/
index bab13dd025a6..8670fb38a40e 100755
--- a/tools/testing/selftests/cpu-hotplug/
+++ b/tools/testing/selftests/cpu-hotplug/
@@ -31,12 +31,17 @@ prerequisite()
 	echo "CPU online/offline summary:"
 	online_cpus=`cat $SYSFS/devices/system/cpu/online`
+	echo "online_cpus = $online_cpus online_max = $online_max"
 	if [[ "$online_cpus" = "$online_max" ]]; then
 		echo "$msg: since there is only one cpu: $online_cpus"
 		exit $ksft_skip
+	present_cpus=`cat $SYSFS/devices/system/cpu/present`
+	present_max=${present_cpus##*-}
+	echo "present_cpus = $present_cpus present_max = $present_max"
 	echo -e "\t Cpus in online state: $online_cpus"
 	offline_cpus=`cat $SYSFS/devices/system/cpu/offline`
@@ -46,6 +51,7 @@ prerequisite()
 	echo -e "\t Cpus in offline state: $offline_cpus"
@@ -151,6 +157,8 @@ online_cpus=0
 while getopts e:ahp: opt; do
 	case $opt in
@@ -190,9 +198,10 @@ if [ $allcpus -eq 0 ]; then
 	online_cpu_expect_success $online_max
 	if [[ $offline_cpus -gt 0 ]]; then
-		echo -e "\t offline to online to offline: cpu $offline_max"
-		online_cpu_expect_success $offline_max
-		offline_cpu_expect_success $offline_max
+		echo -e "\t offline to online to offline: cpu $present_max"
+		online_cpu_expect_success $present_max
+		offline_cpu_expect_success $present_max
+		online_cpu $present_max
 	exit 0

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