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Date:   Tue, 6 Nov 2018 12:37:12 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Waiman Long <longman@redhat.com>
Cc:     Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Ingo Molnar <mingo@redhat.com>, cgroups@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
        kernel-team@fb.com, pjt@google.com, luto@amacapital.net,
        Mike Galbraith <efault@gmx.de>, torvalds@linux-foundation.org,
        Roman Gushchin <guro@fb.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Patrick Bellasi <patrick.bellasi@arm.com>,
        Tom Hromatka <tom.hromatka@oracle.com>
Subject: Re: [PATCH v14 05/12] cpuset: Add an error state to
 cpuset.sched.partition
Message-ID: <20181106113712.GL22431@hirez.programming.kicks-ass.net>
References: <1539635377-22335-1-git-send-email-longman@redhat.com>
 <1539635377-22335-6-git-send-email-longman@redhat.com>
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On Mon, Oct 15, 2018 at 04:29:30PM -0400, Waiman Long wrote:
> Handling error returned by update_parent_subparts_cpumask() in
> update_cpumasks_hier() is problematic as the states may become
> inconsistent. To avoid that and increase flexibility in handling other
> error cases, a new error state (-1) is added to the partition_root_state
> flag. This new error state is set internally and user cannot write this
> value to "cpuset.sched.partition".
> 
> In this error state, the partition root becomes an erroneous one. It is
> no longer a real partition root, but the CS_CPU_EXCLUSIVE flag will
> still be set as it can be changed back to a real one if appropriate
> change happens later on.

I feel this Changelog should be much more explicit about the reasons
this -1 state can happen. As is, I've got no clue.