linux-kernel - Re: [PATCH v2 1/2] cxgb4: sched: Use refcount

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Message-ID: <CANhBUQ2TRr4RuSmjaRYPXHZpVw_-2awXvWNjjdvV_z1yoGdkXA@mail.gmail.com>
Date:   Fri, 2 Aug 2019 22:27:42 +0800
From:   Chuhong Yuan <hslester96@...il.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc:     Vishal Kulkarni <vishal@...lsio.com>,
        "David S . Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] cxgb4: sched: Use refcount_t for refcount

Willem de Bruijn <willemdebruijn.kernel@...il.com> 于2019年8月2日周五 下午9:40写道：
>
> On Fri, Aug 2, 2019 at 4:36 AM Chuhong Yuan <hslester96@...il.com> wrote:
> >
> > refcount_t is better for reference counters since its
> > implementation can prevent overflows.
> > So convert atomic_t ref counters to refcount_t.
> >
> > Signed-off-by: Chuhong Yuan <hslester96@...il.com>
> > ---
> > Changes in v2:
> >   - Convert refcount from 0-base to 1-base.
>
> This changes the initial value from 0 to 1, but does not change the
> release condition. So this introduces an accounting bug?

I have noticed this problem and have checked other files which use refcount_t.
I find although the refcounts are 1-based, they still use
refcount_dec_and_test()
to check whether the resource should be released.
One example is drivers/char/mspec.c.
Therefore I think this is okay and do not change the release condition.