linux-kernel - Re: [PATCH] cgroup/cpuset: Disable cpuset_cpumask_can

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Message-ID: <ZzsLTLEAPMljtaIK@jlelli-thinkpadt14gen4.remote.csb>
Date: Mon, 18 Nov 2024 10:39:24 +0100
From: Juri Lelli <juri.lelli@...hat.com>
To: Waiman Long <llong@...hat.com>
Cc: Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
	Michal Koutný <mkoutny@...e.com>,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH] cgroup/cpuset: Disable cpuset_cpumask_can_shrink() test
 if not load balancing

On 15/11/24 12:55, Waiman Long wrote:
> On 11/15/24 5:54 AM, Juri Lelli wrote:
> > Hi Waiman,
> > 
> > On 14/11/24 13:19, Waiman Long wrote:
> > > With some recent proposed changes [1] in the deadline server code,
> > > it has caused a test failure in test_cpuset_prs.sh when a change
> > > is being made to an isolated partition. This is due to failing
> > > the cpuset_cpumask_can_shrink() check for SCHED_DEADLINE tasks at
> > > validate_change().
> > What sort of change is being made to that isolated partition? Which test
> > is failing from the test_cpuset_prs.sh collection? Asking because I now
> > see "All tests PASSED" running that locally (with all my 3 patches on
> > top of cgroup/for-6.13 w/o this last patch from you).
> 
> The failing test isn't an isolated partition. The actual test failure is
> 
> Test TEST_MATRIX[62] failed result check!
> C0-4:X2-4:S+ C1-4:X2-4:S+:P2 C2-4:X4:P1 . . X5 . . 0 A1:0-4,A2:1-4,A3:2-4
> A1:P0,A2:P-2,A3:P-1
> 
> In this particular case, cgroup A3 has the following setting before the X5
> operation.
> 
> A1/A2/A3/cpuset.cpus: 2-4
> A1/A2/A3/cpuset.cpus.exclusive: 4
> A1/A2/A3/cpuset.cpus.effective: 4
> A1/A2/A3/cpuset.cpus.exclusive.effective: 4
> A1/A2/A3/cpuset.cpus.partition: root

Right, and is this problematic already?

Then the test, I believe, does

# echo 5 >cgroup/A1/A2/cpuset.cpus.exclusive

and that goes through and makes the setup invalid - root domain reconf
and the following

# cat cgroup/A1/cpuset.cpus.partition
member
# cat cgroup/A1/A2/cpuset.cpus.partition
isolated invalid (Parent is not a partition root)
# cat cgroup/A1/A2/A3/cpuset.cpus.partition
root invalid (Parent is an invalid partition root)

Is this what shouldn't happen?