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

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Date:   Tue, 11 Apr 2023 09:46:14 -0600
From:   Logan Gunthorpe <logang@...tatee.com>
To:     Song Liu <song@...nel.org>, Yu Kuai <yukuai1@...weicloud.com>
Cc:     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 2023-04-10 23:26, Song Liu wrote:
> 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.

I agree.

Logan