[PATCH-next 5/6] selftests/cgroup: Check for a single range nohz_full CPUs before running test matrix

[Waiman Long <longman@redhat.com>]

Commit 989ca25c10ca ("selftests/cgroup: Add tests for nohz_full
housekeeping check") adds a nohz_full test matrix that will only be run
when a nohz_full boot parameter cover all the CPUs beyond CPUs 0-7. The
code looks for the first and last CPU numbers in the nohz_full sysfs
file to determine if that criterion is met. However if there are holes in
the range (i.e. has ",") the test matrix may be incorrectly run leading
to unexpected test failure. Fix that by skipping "," and anything after
that to make sure the first range will cover all the remaining CPUs.

Fixes: 989ca25c10ca ("selftests/cgroup: Add tests for nohz_full housekeeping check")
Signed-off-by: Waiman Long <longman@redhat.com>
---
 tools/testing/selftests/cgroup/test_cpuset_prs.sh | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
index 8595b6b4b7bf..5bc144836bdf 100755
--- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
+++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
@@ -111,9 +111,9 @@ echo "" > test/cpuset.cpus
 #
 # If nohz_full CPUs have been reserved at boot time, they should not include
 # CPUs 0-7 as that may fail some of the test cases. On the other hand if the
-# set of nohz_full CPUs includes all the CPUs except 0-7, we can run a special
-# set of housekeeping CPUs exhaustion tests to see if the cpuset code will
-# reject them.
+# set of nohz_full CPUs includes all the CPUs except 0-7 in a single range
+# <first>-<last>, we can run a special set of housekeeping CPUs exhaustion
+# tests to see if the cpuset code will reject them.
 #
 FIRST_NOHZ_FULL_CPU=
 LAST_NOHZ_FULL_CPU=
@@ -124,7 +124,7 @@ NOHZ_FULL_CPUS=
 LAST_PRESENT_CPU=$(cat /sys/devices/system/cpu/present | sed -e "s/.*[,-]//")
 [[ -n "$NOHZ_FULL_CPUS" ]] && {
 	FIRST_NOHZ_FULL_CPU=$(echo $NOHZ_FULL_CPUS | sed -e "s/[,-].*//")
-	LAST_NOHZ_FULL_CPU=$(echo $NOHZ_FULL_CPUS | sed -e "s/.*[,-]//")
+	LAST_NOHZ_FULL_CPU=$(echo $NOHZ_FULL_CPUS | sed -e "s/,.*//;s/.*[-]//")
 	echo "Boot nohz_full CPUs: $NOHZ_FULL_CPUS"
 }
 [[ -n "$FIRST_NOHZ_FULL_CPU" && "$FIRST_NOHZ_FULL_CPU" -le 7 ]] &&
-- 
2.55.0