linux-kernel - Re: [PATCH] files: rcu free files

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Message-ID: <CAHk-=whGEE9vB2Pw6g=+YqnXMz6z5paK3sxNOtN5CB68VQw=Ng@mail.gmail.com>
Date:   Wed, 9 Dec 2020 15:04:55 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Al Viro <viro@...iv.linux.org.uk>
Cc:     Matthew Wilcox <willy@...radead.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jann@...jh.net>
Subject: Re: [PATCH] files: rcu free files_struct

On Wed, Dec 9, 2020 at 3:01 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> rcu_assign_pointer() itself already does the optimization for the case
> of a constant NULL pointer assignment.
>
> So there's no need to manually change things to RCU_INIT_POINTER().

Side note: what should be done instead is to delete the stale comment.
It should have been removed back when the optimization was done in
2016 - see commit 3a37f7275cda ("rcu: No ordering for
rcu_assign_pointer() of NULL")

            Linus