linux-kernel - Re: [PATCH v2 2/7] proc/kcore: replace kclist

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Message-Id: <20180717202753.d49795afde465d04b56efbfb@linux-foundation.org>
Date:   Tue, 17 Jul 2018 20:27:53 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Omar Sandoval <osandov@...ndov.com>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Alexey Dobriyan <adobriyan@...il.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        James Morse <james.morse@....com>,
        Bhupesh Sharma <bhsharma@...hat.com>, kernel-team@...com
Subject: Re: [PATCH v2 2/7] proc/kcore: replace kclist_lock rwlock with
 rwsem

On Tue, 17 Jul 2018 20:24:05 -0700 Omar Sandoval <osandov@...ndov.com> wrote:

> > > --- 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?
> 
> Not in the hotplug notifier (kcore_callback()) anymore, so I need the
> atomic_cmpxchg() in __kcore_update_ram().

Well that's just

	kcore_need_update = 1;

and turning that into an atomic_set doesn't change anything(?).

It's not a harmful change of course, but a bit ... odd.

> That could use a mention in the commit message.

That never hurts ;)