cgroup/cpuset: Expose cpuset.cpus.isolated

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@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup/cpuset: Take isolated CPUs out of workqueue unbound cpumask

To make CPUs in isolated cpuset partition closer in isolation to
the boot time isolated CPUs specified in the "isolcpus" boot command
line option, we need to take those CPUs out of the workqueue unbound
cpumask so that work functions from the unbound workqueues won't run
on those CPUs. Otherwise, they will interfere the user tasks running
on those isolated CPUs.

With the introduction of the workqueue_unbound_exclude_cpumask() helper
function in an earlier commit, those isolated CPUs can now be taken
out from the workqueue unbound cpumask.

This patch also updates cgroup-v2.rst to mention that isolated
CPUs will be excluded from unbound workqueue cpumask as well as
updating test_cpuset_prs.sh to verify the correctness of the new
*cpuset.cpus.isolated file, if available via cgroup_debug option.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

selftests/cgroup: Minor code cleanup and reorganization of test_cpuset_prs.sh

Minor cleanup of test matrix and relocation of test_isolated() function
to prepare for the next patch. There is no functional change.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup/cpuset: Enable invalid to valid local partition transition

When a local partition becomes invalid, it won't transition back to
valid partition automatically if a proper "cpuset.cpus.exclusive" or
"cpuset.cpus" change is made. Instead, system administrators have to
explicitly echo "root" or "isolated" into the "cpuset.cpus.partition"
file at the partition root.

This patch now enables the automatic transition of an invalid local
partition back to valid when there is a proper "cpuset.cpus.exclusive"
or "cpuset.cpus" change.

Automatic transition of an invalid remote partition to a valid one,
however, is not covered by this patch. They still need an explicit
write to "cpuset.cpus.partition" to become valid again.

The test_cpuset_prs.sh test script is updated to add new test cases to
test this automatic state transition.

Reported-by: Pierre Gondois <pierre.gondois@arm.com>
Link: https://lore.kernel.org/lkml/9777f0d2-2fdf-41cb-bd01-19c52939ef42@arm.com
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup/cpuset: Extend test_cpuset_prs.sh to test remote partition

This patch extends the test_cpuset_prs.sh test script to support testing
the new remote partition type and the new "cpuset.cpus.exclusive" and
"cpuset.cpus.exclusive.effective" control files by adding new tests
for them. In addition, the following changes are also made:

1) Run the state transition tests directly under root to ease testing
of remote partition and remove the unneeded test column.
2) Add a column to for the list of expected isolated CPUs and compare
it with the actual value by looking at the state of
/sys/kernel/debug/sched/domains which will be available if the
verbose flag is set.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

selftests: cgroup: Minor code reorganizations

No functional change intended, these small changes are merged into one
commit and they serve as a preparation for an upcoming new testcase.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup/cpuset: Minor updates to test_cpuset_prs.sh

This patch makes the following minor updates to the cpuset partition
testing script test_cpuset_prs.sh.

- Remove online_cpus function call as it will be called anyway on exit
in cleanup.
- Make the enabling of sched/verbose debugfs flag conditional on the
"-v" verbose option and set DELAY_FACTOR to 2 in this case as cpuset
partition operations are likely to be slowed down by enabling that.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

cgroup/cpuset: Fix wrong check in update_parent_subparts_cpumask()

It was found that the check to see if a partition could use up all
the cpus from the parent cpuset in update_parent_subparts_cpumask()
was incorrect. As a result, it is possible to leave parent with no
effective cpu left even if there are tasks in the parent cpuset. This
can lead to system panic as reported in [1].

Fix this probem by updating the check to fail the enabling the partition
if parent's effective_cpus is a subset of the child's cpus_allowed.

Also record the error code when an error happens in update_prstate()
and add a test case where parent partition and child have the same cpu
list and parent has task. Enabling partition in the child will fail in
this case.

[1] https://www.spinics.net/lists/cgroups/msg36254.html

Fixes: f0af1bfc27b5 ("cgroup/cpuset: Relax constraints to partition & cpus changes")
Cc: stable@vger.kernel.org # v6.1
Reported-by: Srinivas Pandruvada <srinivas.pandruvada@intel.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kselftest/cgroup: Add cleanup() to test_cpuset_prs.sh

Install a cleanup function using the trap command for signals EXIT,
SIGINT, SIGQUIT and SIGABRT. The cleanup function will perform:
1. Online the CPUs that were made offline during the test.
2. Removing the cgroups created.
3. Restoring the original /sys/kernel/debug/sched/verbose value,
currently it's left turned on, irrespective of the original
configuration value.

the test performs steps 1 and 2, on the successful runs, but not during
all of the failed runs. With the cleanup(), the system will perform all
three steps during failed/passed test runs.

Signed-off-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kselftest/cgroup: Fix gathering number of CPUs

test_cpuset_prs.sh is failing with the following error:

test_cpuset_prs.sh: line 29: [[: 8
57%: syntax error in expression (error token is "57%")

This is happening because `lscpu | grep "^CPU(s)"` returns two lines in
some systems (such as Debian unstable):

# lscpu | grep "^CPU(s)"
CPU(s): 8
CPU(s) scaling MHz: 55%

This is a simple fix that discard the second line.

Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kselftest/cgroup: Add cpuset v2 partition root state test

Add a test script test_cpuset_prs.sh with a helper program wait_inotify
for exercising the cpuset v2 partition root state code.

Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>