linux-kernel - Re: [PATCH] fs: Safe rcu access to hlist.

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Message-ID: <20171120205801.dtqloltgfxkmfxee@ltop.local>
Date:   Mon, 20 Nov 2017 21:58:02 +0100
From:   Luc Van Oostenryck <luc.vanoostenryck@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Tim Hansen <devtimhansen@...il.com>,
        Al Viro <viro@...IV.linux.org.uk>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        alexander.levin@....verizon.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH] fs: Safe rcu access to hlist.

On Mon, Nov 20, 2017 at 12:42:53PM -0800, Matthew Wilcox wrote:
> 
> I disagree.  The notion of whether a pointer is protected by RCU or not
> is definitely not transient.

Sure. But what about the memory it points to?
It's just 'normal' kernel memory, there is nowhere
something like some 'RCU memory', right?

And the memory accessed through a __rcu annotated
pointer can be legally be accessed with normal
memory operation, because it's only the pointer that
is concerned by the annotation?

-- Luc