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Date:   Tue, 17 Jul 2018 19:38:41 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Omar Sandoval <osandov@osandov.com>
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Eric Biederman <ebiederm@xmission.com>,
        James Morse <james.morse@arm.com>,
        Bhupesh Sharma <bhsharma@redhat.com>, kernel-team@fb.com
Subject: Re: [PATCH v2 2/7] proc/kcore: replace kclist_lock rwlock with
 rwsem
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        <783ba3becc424db45e5d5c93559fc40ef6173f01.1531440458.git.osandov@fb.com>
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On Thu, 12 Jul 2018 17:09:34 -0700 Omar Sandoval <osandov@osandov.com> wrote:

> From: Omar Sandoval <osandov@fb.com>
> 
> Now we only need kclist_lock from user context and at fs init time, and
> the following changes need to sleep while holding the kclist_lock.
> 
> ...
>
> --- a/fs/proc/kcore.c
> +++ b/fs/proc/kcore.c
> @@ -59,8 +59,8 @@ struct memelfnote
>  };
>  
>  static LIST_HEAD(kclist_head);
> -static DEFINE_RWLOCK(kclist_lock);
> -static int kcore_need_update = 1;
> +static DECLARE_RWSEM(kclist_lock);
> +static atomic_t kcore_need_update = ATOMIC_INIT(1);

It's unclear why kcore_need_update was changed to atomic_t - it's still
updated under kclist_lock?

Maybe it's for a later patch.