From: Omar Sandoval <osandov@fb.com>
Date: Mon, 11 Jun 2018 18:31:57 +0000 (-0700)
Subject: block/008: don't try to offline all CPUs if all CPUs are hotpluggable
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=8de43b4b284cc8eaba0bb0a04604089737b3e8b5;p=users%2Fsagi%2Fblktests.git

block/008: don't try to offline all CPUs if all CPUs are hotpluggable

Chen Rong reported that if CPU0 is hotpluggable (because we booted with
cpu0_hotplug or CONFIG_BOOTPARAM_HOTPLUG_CPU0 was enabled), block/008
can try to offline all CPUs at once, which isn't allowed. Fix it by
repeatedly offlining as many CPUs as is allowed and onlining all CPUs,
instead of the previous approach of randomly onlining/offlining. This is
better than the previous approach because we won't try to online already
online CPUs and offline already offline CPUs. Closes #23.

Reported-by: Chen Rong <chenr.fnst@cn.fujitsu.com>
Signed-off-by: Omar Sandoval <osandov@fb.com>
---

diff --git a/common/cpuhotplug b/common/cpuhotplug
index 6a790fe..70b284f 100644
--- a/common/cpuhotplug
+++ b/common/cpuhotplug
@@ -17,13 +17,15 @@
 # You should have received a copy of the GNU General Public License
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
-# Also initializes the HOTPLUGGABLE_CPUS array.
+# Also initializes the ALL_CPUS and HOTPLUGGABLE_CPUS arrays.
 _have_cpu_hotplug() {
+	ALL_CPUS=()
 	HOTPLUGGABLE_CPUS=()
 	CPUS_ONLINE_SAVED=()
 
 	local cpu_dir cpu
 	for cpu_dir in /sys/devices/system/cpu/cpu+([0-9]); do
+		ALL_CPUS+=("$cpu")
 		if [[ -w ${cpu_dir}/online ]]; then
 			cpu="${cpu_dir#/sys/devices/system/cpu/cpu}"
 			HOTPLUGGABLE_CPUS+=("$cpu")
@@ -31,7 +33,7 @@ _have_cpu_hotplug() {
 		fi
 	done
 
-	if [[ ${#HOTPLUGGABLE_CPUS[@]} -eq 0 ]]; then
+	if [[ ${#ALL_CPUS[@]} -eq 1 || ${#HOTPLUGGABLE_CPUS[@]} -eq 0 ]]; then
 		SKIP_REASON="CPU hotplugging is not supported"
 		return 1
 	fi
@@ -40,10 +42,10 @@ _have_cpu_hotplug() {
 
 _online_cpu() {
 	RESTORE_CPUS_ONLINE=1
-	echo 1 >"/sys/devices/system/cpu/cpu$1/online"
+	echo 1 > "/sys/devices/system/cpu/cpu$1/online"
 }
 
 _offline_cpu() {
 	RESTORE_CPUS_ONLINE=1
-	echo 0 >"/sys/devices/system/cpu/cpu$1/online"
+	echo 0 > "/sys/devices/system/cpu/cpu$1/online"
 }
diff --git a/tests/block/008 b/tests/block/008
index db2a72a..4534dc3 100755
--- a/tests/block/008
+++ b/tests/block/008
@@ -38,14 +38,45 @@ test_device() {
 	# start fio job
 	_run_fio_rand_io --filename="$TEST_DEV" --size="$size" &
 
-	# while job is running, hotplug CPUs randomly
-	while kill -0 $! 2>/dev/null; do
-		idx=$((RANDOM % ${#HOTPLUGGABLE_CPUS[@]}))
-		if (( RANDOM % 2 )); then
-			_online_cpu "${HOTPLUGGABLE_CPUS[$idx]}"
+	local online_cpus=()
+	local offline_cpus=()
+	local offlining=1
+	local max_offline=${#HOTPLUGGABLE_CPUS[@]}
+	if [[ ${#HOTPLUGGABLE_CPUS[@]} -eq ${#ALL_CPUS[@]} ]]; then
+		(( max_offline-- ))
+	fi
+	for cpu in "${HOTPLUGGABLE_CPUS[@]}"; do
+		if (( "$(cat "/sys/devices/system/cpu/cpu${cpu}/online")" )); then
+			online_cpus+=("$cpu")
+		else
+			offline_cpus+=("$cpu")
+		fi
+	done
+
+	# while job is running, hotplug CPUs
+	while kill -0 $! 2> /dev/null; do
+		if (( offlining && ${#offline_cpus[@]} == max_offline )); then
+			offlining=0
+		elif (( ! offlining && ${#online_cpus[@]} == ${#HOTPLUGGABLE_CPUS[@]} )); then
+			offlining=1
+		fi
+
+		if (( offlining )); then
+			idx=$((RANDOM % ${#online_cpus[@]}))
+			echo "offlining $idx (online=${online_cpus[@]} offline=${offline_cpus[@]})" >> /dev/kmsg
+			_offline_cpu "${online_cpus[$idx]}"
+			offline_cpus+=("${online_cpus[$idx]}")
+			unset online_cpus[$idx]
+			online_cpus=("${online_cpus[@]}")
 		else
-			_offline_cpu "${HOTPLUGGABLE_CPUS[$idx]}"
+			idx=$((RANDOM % ${#offline_cpus[@]}))
+			echo "onlining $idx (online=${online_cpus[@]} offline=${offline_cpus[@]})" >> /dev/kmsg
+			_online_cpu "${offline_cpus[$idx]}"
+			online_cpus+=("${offline_cpus[$idx]}")
+			unset offline_cpus[$idx]
+			offline_cpus=("${offline_cpus[@]}")
 		fi
+
 		sleep .2
 	done