[PATCH] cgroup/cpuset: Expose cpuset.cpus.isolated

From: Waiman Long
Date: Mon Nov 27 2023 - 14:51:25 EST


The root-only cpuset.cpus.isolated control file shows the current set
of isolated CPUs in isolated partitions. This control file is currently
exposed only with the cgroup_debug boot command line option which also
adds the ".__DEBUG__." prefix. This is actually a useful control file if
users want to find out which CPUs are currently in an isolated state by
the cpuset controller. Remove CFTYPE_DEBUG flag for this control file and
make it available by default without any prefix.

The test_cpuset_prs.sh test script and the cgroup-v2.rst documentation
file are also updated accordingly. Minor code change is also made in
test_cpuset_prs.sh to avoid false test failure when running on debug
kernel.

Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
---
Documentation/admin-guide/cgroup-v2.rst | 7 ++++
kernel/cgroup/cpuset.c | 2 +-
.../selftests/cgroup/test_cpuset_prs.sh | 32 +++++++++++--------
3 files changed, 26 insertions(+), 15 deletions(-)

diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index cf5651a11df8..30f6ff2eba47 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -2316,6 +2316,13 @@ Cpuset Interface Files
treated to have an implicit value of "cpuset.cpus" in the
formation of local partition.

+ cpuset.cpus.isolated
+ A read-only and root cgroup only multiple values file.
+
+ This file shows the set of all isolated CPUs used in existing
+ isolated partitions. It will be empty if no isolated partition
+ is created.
+
cpuset.cpus.partition
A read-write single value file which exists on non-root
cpuset-enabled cgroups. This flag is owned by the parent cgroup
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 1bad4007ff4b..2a16df86c55c 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3974,7 +3974,7 @@ static struct cftype dfl_files[] = {
.name = "cpus.isolated",
.seq_show = cpuset_common_seq_show,
.private = FILE_ISOLATED_CPULIST,
- .flags = CFTYPE_ONLY_ON_ROOT | CFTYPE_DEBUG,
+ .flags = CFTYPE_ONLY_ON_ROOT,
},

{ } /* terminate */
diff --git a/tools/testing/selftests/cgroup/test_cpuset_prs.sh b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
index 7b7c4c2b6d85..b5eb1be2248c 100755
--- a/tools/testing/selftests/cgroup/test_cpuset_prs.sh
+++ b/tools/testing/selftests/cgroup/test_cpuset_prs.sh
@@ -508,7 +508,7 @@ dump_states()
XECPUS=$DIR/cpuset.cpus.exclusive.effective
PRS=$DIR/cpuset.cpus.partition
PCPUS=$DIR/.__DEBUG__.cpuset.cpus.subpartitions
- ISCPUS=$DIR/.__DEBUG__.cpuset.cpus.isolated
+ ISCPUS=$DIR/cpuset.cpus.isolated
[[ -e $CPUS ]] && echo "$CPUS: $(cat $CPUS)"
[[ -e $XCPUS ]] && echo "$XCPUS: $(cat $XCPUS)"
[[ -e $ECPUS ]] && echo "$ECPUS: $(cat $ECPUS)"
@@ -593,17 +593,17 @@ check_cgroup_states()

#
# Get isolated (including offline) CPUs by looking at
-# /sys/kernel/debug/sched/domains and *cpuset.cpus.isolated control file,
+# /sys/kernel/debug/sched/domains and cpuset.cpus.isolated control file,
# if available, and compare that with the expected value.
#
# Note that isolated CPUs from the sched/domains context include offline
# CPUs as well as CPUs in non-isolated 1-CPU partition. Those CPUs may
-# not be included in the *cpuset.cpus.isolated control file which contains
+# not be included in the cpuset.cpus.isolated control file which contains
# only CPUs in isolated partitions.
#
# $1 - expected isolated cpu list(s) <isolcpus1>{,<isolcpus2>}
# <isolcpus1> - expected sched/domains value
-# <isolcpus2> - *cpuset.cpus.isolated value = <isolcpus1> if not defined
+# <isolcpus2> - cpuset.cpus.isolated value = <isolcpus1> if not defined
#
check_isolcpus()
{
@@ -611,7 +611,7 @@ check_isolcpus()
ISOLCPUS=
LASTISOLCPU=
SCHED_DOMAINS=/sys/kernel/debug/sched/domains
- ISCPUS=${CGROUP2}/.__DEBUG__.cpuset.cpus.isolated
+ ISCPUS=${CGROUP2}/cpuset.cpus.isolated
if [[ $EXPECT_VAL = . ]]
then
EXPECT_VAL=
@@ -692,14 +692,18 @@ test_fail()
null_isolcpus_check()
{
[[ $VERBOSE -gt 0 ]] || return 0
- pause 0.02
- check_isolcpus "."
- if [[ $? -ne 0 ]]
- then
- echo "Unexpected isolated CPUs: $ISOLCPUS"
- dump_states
- exit 1
- fi
+ # Retry a few times before printing error
+ RETRY=0
+ while [[ $RETRY -lt 5 ]]
+ do
+ pause 0.01
+ check_isolcpus "."
+ [[ $? -eq 0 ]] && return 0
+ ((RETRY++))
+ done
+ echo "Unexpected isolated CPUs: $ISOLCPUS"
+ dump_states
+ exit 1
}

#
@@ -776,7 +780,7 @@ run_state_test()
#
NEWLIST=$(cat cpuset.cpus.effective)
RETRY=0
- while [[ $NEWLIST != $CPULIST && $RETRY -lt 5 ]]
+ while [[ $NEWLIST != $CPULIST && $RETRY -lt 8 ]]
do
# Wait a bit longer & recheck a few times
pause 0.01
--
2.39.3