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From: Tejun Heo <tj@kernel.org>
To: Waiman Long <longman@redhat.com>
Cc: "Michal Koutný" <mkoutny@suse.com>,
	"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>
Subject: Re: [PATCH v9 6/7] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst
Date: Wed, 12 Jan 2022 11:21:00 -1000	[thread overview]
Message-ID: <Yd9GPLytGQ6XpYK6@slm.duckdns.org> (raw)
In-Reply-To: <58c06961-ffc4-27d7-01d2-4c91b0c9161d@redhat.com>

Hello,

On Wed, Dec 15, 2021 at 01:55:05PM -0500, Waiman Long wrote:
> How about we allow transition to an invalid partition state but still return
> an error?

Like -EAGAIN as Michal suggested? I don't know. I understand the motivation
but one problem is that error return usually means that the operation didn't
change the state of the system and that holds even for -EAGAIN. So, we'd be
trading one locally jarring thing (this thing is asynchrnous and the actual
state transitions should be monitored separately) to another one which is
jarring in a wider context (this thing returned error but the system state
changed anyway). To me, the latter seems noticeably worse given how common
the assumption that an error return indicate that nothing actually happened.

We have other cases where we split operation submissions and completions
(aios being the obvious one) but I don't think we have any where -EAGAIN
indicates successful initiation of an operation. At least I hope not.

Thanks.

-- 
tejun

  reply	other threads:[~2022-01-12 21:21 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-12-05 18:32 [PATCH v9 0/7] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long
2021-12-05 18:32 ` [PATCH v9 1/7] cgroup/cpuset: Don't let child cpusets restrict parent in default hierarchy Waiman Long
2021-12-13 20:41   ` Tejun Heo
2021-12-15 12:23     ` Michal Koutný
2021-12-15 17:59       ` Waiman Long
2021-12-17 15:48         ` [PATCH] cgroup/cpuset: Make child cpusets restrict parents on v1 hierarchy Michal Koutný
2021-12-17 16:34           ` Waiman Long
2022-01-12 21:25           ` Tejun Heo
2021-12-05 18:32 ` [PATCH v9 2/7] cgroup/cpuset: Allow no-task partition to have empty cpuset.cpus.effective Waiman Long
2021-12-13 20:45   ` Tejun Heo
2021-12-15  3:24     ` Waiman Long
2021-12-15 10:36       ` Michal Koutný
2021-12-05 18:32 ` [PATCH v9 3/7] cgroup/cpuset: Refining features and constraints of a partition Waiman Long
2021-12-15 14:49   ` Michal Koutný
2021-12-15 16:29     ` Waiman Long
2021-12-16  9:28       ` Michal Koutný
2021-12-05 18:32 ` [PATCH v9 4/7] cgroup/cpuset: Add a new isolated cpus.partition type Waiman Long
2022-01-12 15:21   ` Peter Zijlstra
2022-01-12 15:40     ` Waiman Long
2022-01-12 21:23       ` Tejun Heo
2021-12-05 18:32 ` [PATCH v9 5/7] cgroup/cpuset: Show invalid partition reason string Waiman Long
2021-12-05 18:32 ` [PATCH v9 6/7] cgroup/cpuset: Update description of cpuset.cpus.partition in cgroup-v2.rst Waiman Long
2021-12-13 21:00   ` Tejun Heo
2021-12-15 14:44     ` Michal Koutný
2021-12-15 18:16       ` Waiman Long
2021-12-15 18:35         ` Tejun Heo
2021-12-15 18:55           ` Waiman Long
2022-01-12 21:21             ` Tejun Heo [this message]
2021-12-05 18:32 ` [PATCH v9 7/7] kselftest/cgroup: Add cpuset v2 partition root state test Waiman Long
2021-12-09 15:39 ` [PATCH v9 0/7] cgroup/cpuset: Add new cpuset partition type & empty effecitve cpus Waiman Long

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