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From:   Josh Don <joshdon@google.com>
Date:   Tue, 15 Nov 2022 19:01:31 -0800
Message-ID: <CABk29Nvw8XMrc2_9CAUZb=rO_vddGjsfZ1s3mRQyShANDhtZnw@mail.gmail.com>
Subject: Re: [PATCH v2] sched: async unthrottling for cfs bandwidth
To:     =?UTF-8?Q?Michal_Koutn=C3=BD?= <mkoutny@suse.com>
Cc:     Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        Daniel Bristot de Oliveira <bristot@redhat.com>,
        Valentin Schneider <vschneid@redhat.com>,
        linux-kernel@vger.kernel.org
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On Wed, Nov 2, 2022 at 9:59 AM Michal Koutn=C3=BD <mkoutny@suse.com> wrote:
>
> Also, can a particular cfs_rq be on both cfs_b->throttled_csd_list and
> cfs_b->throttled_cfs_rq lists at any moment?
> I wonder if having a single list_head node in cfs_rq would be feasible
> (and hence enforcing this constraint in data).

After more thought, I realized that we can't reuse the throttled_list
list_head, since that would potentially break the lockless traversal
of a concurrent list_for_each_entry_rcu() (ie. if we removed the
element from the throttled list and then added it to the CSD list).

- Josh