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

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Message-ID: <daa344fe-9d8d-16f9-aded-513f250928b9@huaweicloud.com>
Date:   Tue, 11 Apr 2023 09:34:48 +0800
From:   Yu Kuai <yukuai1@...weicloud.com>
To:     Song Liu <song@...nel.org>, 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()

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);

> 
> 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.

Thanks,
Kuai
> 
> Thanks,
> Song
> .
>