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Subject: Re: [PATCH] list: Remove unnecessary WRITE_ONCE()
From:   Alan Huang <mmpgouride@gmail.com>
In-Reply-To: <CANn89iJgM1-SBzHXDdur+MgK2cBBeOacKOWz=zPyEa2mee3fOw@mail.gmail.com>
Date:   Mon, 19 Jun 2023 19:39:04 +0800
Cc:     paulmck@kernel.org, linux-kernel@vger.kernel.org
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Message-Id: <4E6A0BCB-02F4-4AB9-BE56-7FC7C15A6B2C@gmail.com>
References: <20230619090336.145738-1-mmpgouride@gmail.com>
 <CANn89iJgM1-SBzHXDdur+MgK2cBBeOacKOWz=zPyEa2mee3fOw@mail.gmail.com>
To:     Eric Dumazet <edumazet@google.com>
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> 2023=E5=B9=B46=E6=9C=8819=E6=97=A5 19:02=EF=BC=8CEric Dumazet =
<edumazet@google.com> =E5=86=99=E9=81=93=EF=BC=9A
>=20
> On Mon, Jun 19, 2023 at 11:03=E2=80=AFAM Alan Huang =
<mmpgouride@gmail.com> wrote:
>>=20
>> 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().
>=20
> Why are they unnecessary ?

There is no reader locklessly read ->next.

These functions are protected by something like spin_lock, only the =
thread running=20
the function can access ->next.

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