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From: Waiman Long <llong@redhat.com>
To: Tejun Heo <tj@kernel.org>, Waiman Long <llong@redhat.com>
Cc: "Zefan Li" <lizefan.x@bytedance.com>,
	"Johannes Weiner" <hannes@cmpxchg.org>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Shuah Khan" <shuah@kernel.org>,
	cgroups@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Roman Gushchin" <guro@fb.com>, "Phil Auld" <pauld@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Juri Lelli" <juri.lelli@redhat.com>,
	"Frederic Weisbecker" <frederic@kernel.org>,
	"Marcelo Tosatti" <mtosatti@redhat.com>,
	"Michal Koutný" <mkoutny@suse.com>
Subject: Re: [PATCH v4 4/6] cgroup/cpuset: Allow non-top parent partition root to distribute out all CPUs
Date: Wed, 11 Aug 2021 14:46:24 -0400	[thread overview]
Message-ID: <ef02d96b-325c-87f6-a6a3-d840feefef24@redhat.com> (raw)
In-Reply-To: <YRQVFkNX5DcKixzy@slm.duckdns.org>

On 8/11/21 2:21 PM, Tejun Heo wrote:
> On Wed, Aug 11, 2021 at 02:18:17PM -0400, Waiman Long wrote:
>> I don't think that is true. A task can reside anywhere in the cgroup
>> hierarchy. I have encountered no problem moving tasks around.
> Oh, that shouldn't be happening with controllers enabled. Can you please
> share a repro?

I have done further testing. Enabling controllers won't prohibit moving 
a task into a parent cgroup as long as the child cgroups have no tasks. 
Once the child cgroup has task, moving another task to the parent is not 
allowed (-EBUSY). Similarly if a parent cgroup has tasks, you can't put 
new tasks into the child cgroup. I don't realize that we have such 
constraints as I usually do my testing with a cgroup hierarchy with no 
tasks initially. Anyway, a new lesson learned.

I will try to see how to address that in the patch, but the additional 
check added is still valid in some special case.

Cheers,
Longman






  reply	other threads:[~2021-08-11 18:46 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-11  3:06 [PATCH-cgroup v4 0/6] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long
2021-08-11  3:06 ` [PATCH v4 1/6] cgroup/cpuset: Enable event notification when partition state changes Waiman Long
2021-08-11 18:04   ` Tejun Heo
2021-08-11  3:06 ` [PATCH v4 2/6] cgroup/cpuset: Properly handle partition root tree Waiman Long
2021-08-11 18:08   ` Tejun Heo
2021-08-11 19:27     ` Waiman Long
2021-08-12 22:18       ` Tejun Heo
2021-08-12 22:56         ` Waiman Long
2021-08-13 16:07           ` Tejun Heo
2021-08-11  3:06 ` [PATCH v4 3/6] cgroup/cpuset: Add a new isolated cpus.partition type Waiman Long
2021-08-11  3:06 ` [PATCH v4 4/6] cgroup/cpuset: Allow non-top parent partition root to distribute out all CPUs Waiman Long
2021-08-11 18:13   ` Tejun Heo
2021-08-11 18:18     ` Waiman Long
2021-08-11 18:21       ` Tejun Heo
2021-08-11 18:46         ` Waiman Long [this message]
2021-08-12 21:51           ` Tejun Heo
2021-08-11  3:06 ` [PATCH v4 5/6] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Waiman Long
2021-08-11 18:15   ` Tejun Heo
2021-08-11 18:19     ` Waiman Long
2021-08-11  3:06 ` [PATCH v4 6/6] kselftest/cgroup: Add cpuset v2 partition root state test Waiman Long

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