linux-kernel - Re: fs_struct refcounting: spinlock vs atomic

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Message-ID: <CAFLxGvz2t8rnEQh4VBJ8v3b66GKA5DY3iMk33jnMP664+RMubw@mail.gmail.com>
Date:   Thu, 15 Feb 2018 10:14:27 +0100
From:   Richard Weinberger <richard.weinberger@...il.com>
To:     Enrico Weigelt <lkml@...ux.net>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: fs_struct refcounting: spinlock vs atomic

On Wed, Feb 14, 2018 at 10:13 PM, Enrico Weigelt <lkml@...ux.net> wrote:
> Hi folks,
>
>
> in fork.c, a spinlock is held for fs_struct refcounting, while other
> places - eg. switch_task_namespaces uses atomic_dec_and_test() on
> the nsproxy.
>
> What's the exact difference here ? Could the atomic counting also used
> for fs_struct ?

Well, the spinlock protects more than just the counter. So atomic won't do it.

-- 
Thanks,
//richard