Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <20230410113559.1610455-1-yukuai1@huaweicloud.com>
 <20230410113559.1610455-2-yukuai1@huaweicloud.com> <CAPhsuW7rUQ9KFxCQw-iAAA64=x==b-Qu0nnp32TXn-85Okb00w@mail.gmail.com>
 <daa344fe-9d8d-16f9-aded-513f250928b9@huaweicloud.com>
In-Reply-To: <daa344fe-9d8d-16f9-aded-513f250928b9@huaweicloud.com>
From:   Song Liu <song@kernel.org>
Date:   Mon, 10 Apr 2023 22:26:57 -0700
Message-ID: <CAPhsuW7bBaVsneBHYqwN3yd5k3sg6ZUFqEJad3yOD0=N-e411g@mail.gmail.com>
Subject: Re: [PATCH -next v5 1/6] md: pass a md_thread pointer to md_register_thread()
To:     Yu Kuai <yukuai1@huaweicloud.com>
Cc:     logang@deltatee.com, linux-kernel@vger.kernel.org,
        linux-raid@vger.kernel.org, yi.zhang@huawei.com,
        yangerkun@huawei.com, "yukuai (C)" <yukuai3@huawei.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Mon, Apr 10, 2023 at 6:34=E2=80=AFPM Yu Kuai <yukuai1@huaweicloud.com> w=
rote:
>
> Hi,
>
> =E5=9C=A8 2023/04/11 9:15, Song Liu =E5=86=99=E9=81=93:
> > On Mon, Apr 10, 2023 at 4:37=E2=80=AFAM Yu Kuai <yukuai1@huaweicloud.co=
m> wrote:
> >>
> >> From: Yu Kuai <yukuai3@huawei.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_threa=
d *),
> >                 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