From: Omar Sandoval <osandov@osandov.com>
To: Andrew Morton <akpm@linux-foundation.org>
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
Date: Tue, 17 Jul 2018 20:36:34 -0700 [thread overview]
Message-ID: <20180718033634.GD29351@vader> (raw)
In-Reply-To: <20180717202753.d49795afde465d04b56efbfb@linux-foundation.org>
On Tue, Jul 17, 2018 at 08:27:53PM -0700, Andrew Morton wrote:
> On Tue, 17 Jul 2018 20:24:05 -0700 Omar Sandoval <osandov@osandov.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.
The change from read, ..., write to cmpxchg in __kcore_update_ram() is
the important part, not the change from = to atomic_set(). I needed to
change that because now kcore_need_update could potentially be set again
by the hotplug notifier while we're in __kcore_update_ram(). But I'll
just put all of this in the commit message in v3 :)
> > That could use a mention in the commit message.
>
> That never hurts ;)
next prev parent reply other threads:[~2018-07-18 4:12 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-13 0:09 [PATCH v2 0/7] /proc/kcore improvements Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 1/7] proc/kcore: don't grab lock for kclist_add() Omar Sandoval
2018-07-18 2:35 ` Andrew Morton
2018-07-18 3:19 ` Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 2/7] proc/kcore: replace kclist_lock rwlock with rwsem Omar Sandoval
2018-07-18 2:38 ` Andrew Morton
2018-07-18 3:24 ` Omar Sandoval
2018-07-18 3:27 ` Andrew Morton
2018-07-18 3:36 ` Omar Sandoval [this message]
2018-07-13 0:09 ` [PATCH v2 3/7] proc/kcore: fix memory hotplug vs multiple opens race Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 4/7] proc/kcore: hold lock during read Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 5/7] proc/kcore: clean up ELF header generation Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 6/7] proc/kcore: optimize multiple page reads Omar Sandoval
2018-07-13 0:09 ` [PATCH v2 7/7] proc/kcore: add vmcoreinfo note to /proc/kcore Omar Sandoval
2018-07-18 2:44 ` Andrew Morton
2018-07-18 3:27 ` Omar Sandoval
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