linux-kernel - Re: [PATCH 05/10] writeback: support

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Message-ID: <4A51FE33.3070702@gmail.com>
Date:	Mon, 06 Jul 2009 16:37:55 +0300
From:	Artem Bityutskiy <dedekind1@...il.com>
To:	Jens Axboe <jens.axboe@...cle.com>
CC:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	chris.mason@...cle.com, david@...morbit.com, hch@...radead.org,
	akpm@...ux-foundation.org, jack@...e.cz,
	yanmin_zhang@...ux.intel.com, richard@....demon.co.uk,
	damien.wyart@...e.fr, fweisbec@...il.com, Alan.Brunelle@...com
Subject: Re: [PATCH 05/10] writeback: support > 1 flusher thread per bdi

Jens Axboe wrote:
> +static void bdi_queue_work(struct backing_dev_info *bdi, struct bdi_work *work)
> +{
> +	if (work) {
> +		work->seen = 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.

-- 
Best Regards,
Artem Bityutskiy (Артём Битюцкий)
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