From mboxrd@z Thu Jan  1 00:00:00 1970
From: Artem Bityutskiy <dedekind1@gmail.com>
Subject: Re: [PATCH 05/10] writeback: support > 1 flusher thread per bdi
Date: Mon, 06 Jul 2009 16:37:55 +0300
Message-ID: <4A51FE33.3070702@gmail.com>
References: <1245926523-21959-1-git-send-email-jens.axboe@oracle.com> <1245926523-21959-6-git-send-email-jens.axboe@oracle.com>
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Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	chris.mason@oracle.com, david@fromorbit.com, hch@infradead.org,
	akpm@linux-foundation.org, jack@suse.cz,
	yanmin_zhang@linux.intel.com, richard@rsk.demon.co.uk,
	damien.wyart@free.fr, fweisbec@gmail.com, Alan.Brunelle@hp.com
To: Jens Axboe <jens.axboe@oracle.com>
Return-path: <linux-kernel-owner+glk-linux-kernel-3=40m.gmane.org-S1755984AbZGFNjg@vger.kernel.org>
In-Reply-To: <1245926523-21959-6-git-send-email-jens.axboe@oracle.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: linux-fsdevel.vger.kernel.org

Jens Axboe wrote:
> +static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_=
work *work)
> +{
> +	if (work) {
> +		work->seen =3D bdi->wb_mask;
> +		BUG_ON(!work->seen);
> +		atomic_set(&work->pending, bdi->wb_cnt);
> +		BUG_ON(!bdi->wb_cnt);
> +
> +		/*
> +		 * Make sure stores are seen before it appears on the list
> +		 */
> +		smp_mb();
> +
> +		spin_lock(&bdi->wb_lock);
> +		list_add_tail_rcu(&work->list, &bdi->work_list);
> +		spin_unlock(&bdi->wb_lock);
> +	}

Doesn't spin_lock() include an implicit memory barrier?
After &bdi->wb_lock is acquired, it is guaranteed that all
memory operations are finished.

--=20
Best Regards,
Artem Bityutskiy (=D0=90=D1=80=D1=82=D1=91=D0=BC =D0=91=D0=B8=D1=82=D1=8E=
=D1=86=D0=BA=D0=B8=D0=B9)