linux-kernel - Re: [PATCH] list: Remove unnecessary WRITE

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Message-Id: <4E6A0BCB-02F4-4AB9-BE56-7FC7C15A6B2C@gmail.com>
Date:   Mon, 19 Jun 2023 19:39:04 +0800
From:   Alan Huang <mmpgouride@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     paulmck@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] list: Remove unnecessary WRITE_ONCE()


> 2023年6月19日 19:02，Eric Dumazet <edumazet@...gle.com> 写道：
> 
> On Mon, Jun 19, 2023 at 11:03 AM Alan Huang <mmpgouride@...il.com> wrote:
>> 
>> Commit c54a2744497d("list: Add hlist_unhashed_lockless()") added
>> various WRITE_ONCE() to pair with the READ_ONCE() in
>> hlist_unhashed_lockless(), but there is no need to protect
>> ->next with WRITE_ONCE(). Therefore, this commit removes those
>> unnecessary WRITE_ONCE().
> 
> Why are they unnecessary ?

There is no reader locklessly read ->next.

These functions are protected by something like spin_lock, only the thread running 
the function can access ->next.

> They seem just fine to me.
> Please elaborate.