linux-kernel - Re: [PATCH -next v5 1/6] md: pass a md_thread pointer to md_register

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Message-ID: <CAPhsuW7bBaVsneBHYqwN3yd5k3sg6ZUFqEJad3yOD0=N-e411g@mail.gmail.com>
Date:   Mon, 10 Apr 2023 22:26:57 -0700
From:   Song Liu <song@...nel.org>
To:     Yu Kuai <yukuai1@...weicloud.com>
Cc:     logang@...tatee.com, linux-kernel@...r.kernel.org,
        linux-raid@...r.kernel.org, yi.zhang@...wei.com,
        yangerkun@...wei.com, "yukuai (C)" <yukuai3@...wei.com>
Subject: Re: [PATCH -next v5 1/6] md: pass a md_thread pointer to md_register_thread()

On Mon, Apr 10, 2023 at 6:34 PM Yu Kuai <yukuai1@...weicloud.com> wrote:
>
> Hi,
>
> 在 2023/04/11 9:15, Song Liu 写道:
> > On Mon, Apr 10, 2023 at 4:37 AM Yu Kuai <yukuai1@...weicloud.com> wrote:
> >>
> >> From: Yu Kuai <yukuai3@...wei.com>
> >>
> >> Prepare to protect md_thread with rcu, there are no functional changes.
> >
> > Why do we need this change? To add __rcu later?
>
> Add __rcu is one reason, more importantly is to assign md_thread inside
> md_register_thread in patch 6:
>
> rcu_assign_pointer(*threadp, thread);

Got it.

> >
> > Can we do something like:
> >
> > struct md_thread __rcu *md_register_thread(void (*run) (struct md_thread *),
> >                 struct mddev *mddev, const char *name)
>
> I think this is not necessary, if we don't want to change api, we must
> use rcu_assign_pointer for each caller to set md_thread.

I think it is better to use rcu_assign_pointer at the caller side.

Thanks,
Song