linux-kernel - Re: [RFC PATCH] locks:Remove spinlock in unshare

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Message-ID: <CAOGi=dNniSgkUtJPfaYLAbR+_8DMFdU59mx7hf8Otj_VjDF_dQ@mail.gmail.com>
Date:   Mon, 16 Mar 2020 21:25:42 +0800
From:   Ling Ma <ling.ma.program@...il.com>
To:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>
Cc:     "ling.ma" <ling.ml@...fin.com>
Subject: Re: [RFC PATCH] locks:Remove spinlock in unshare_files

Any comments ?

Thanks
Ling

<ling.ma.program@...il.com> 于2020年3月13日周五 上午11:09写道：
>
> From: Ma Ling <ling.ml@...fin.com>
>
> Processor support atomic operation for long/int/short/char type,
> we use the feature to avoid spinlock, which cost hundreds cycles.
>
> Appreciate your comments
> Ling
>
> Signed-off-by: Ma Ling <ling.ml@...fin.com>
> ---
>  kernel/fork.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/kernel/fork.c b/kernel/fork.c
> index 60a1295..fe54600 100644
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -3041,9 +3041,7 @@ int unshare_files(struct files_struct **displaced)
>                 return error;
>         }
>         *displaced = task->files;
> -       task_lock(task);
> -       task->files = copy;
> -       task_unlock(task);
> +       WRITE_ONCE(task->files, copy);
>         return 0;
>  }
>
> --
> 1.8.3.1
>