linux-kernel - Re: [PATCH] md/raid5: play nice with PREEMPT

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Message-ID: <CAPhsuW7w9e2xNwacStU_Km9Q8evP5DcVatF8fW1DnKxJJ0L3NA@mail.gmail.com>
Date:   Tue, 16 Nov 2021 23:35:33 -0800
From:   Song Liu <song@...nel.org>
To:     Davidlohr Bueso <dave@...olabs.net>
Cc:     linux-raid <linux-raid@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH] md/raid5: play nice with PREEMPT_RT

On Mon, Nov 15, 2021 at 5:23 PM Davidlohr Bueso <dave@...olabs.net> wrote:
>
> raid_run_ops() relies on the implicitly disabled preemption for
> its percpu ops, although this is really about CPU locality. This
> breaks RT semantics as it can take regular (and thus sleeping)
> spinlocks, such as stripe_lock.
>
> Add a local_lock such that non-RT does not change and continues
> to be just map to preempt_disable/enable, but makes RT happy as
> the region will use a per-CPU spinlock and thus be preemptible
> and still guarantee CPU locality.
>
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>

Applied to md-next.

Thanks,
Song