[Cbe-oss-dev] [PATCH 04/15] ps3vram: Replace mutex by spinlock + list

[Geert Uytterhoeven]

On Fri, 8 May 2009, Andrew Morton wrote:
> On Fri,  8 May 2009 16:01:13 +0200
> Geert Uytterhoeven <Geert.Uytterhoeven at sonycom.com> wrote:
> 
> > +static int ps3vram_make_request(struct request_queue *q, struct bio *bio)
> > +{
> > +	struct ps3_system_bus_device *dev = q->queuedata;
> > +	struct ps3vram_priv *priv = dev->core.driver_data;
> > +
> > +	dev_dbg(&dev->core, "%s\n", __func__);
> > +
> > +	spin_lock_irq(&priv->lock);
> > +	if (priv->tail) {
> > +		priv->tail->bi_next = bio;
> > +		priv->tail = bio;
> > +		spin_unlock_irq(&priv->lock);
> > +		return 0;
                ^^^^^^^^
> > +	}
> > +
> > +	priv->tail = bio;
> > +	spin_unlock_irq(&priv->lock);
> > +
> > +	do {
> > +		bio = ps3vram_do_bio(dev, bio);
> > +	} while (bio);
> 
> Is there something which prevents two threads of control from walking
> the same list at the same time?

Sure: only the thread who adds the first request to the empty list will walk
the list later.

With kind regards,

Geert Uytterhoeven
Software Architect
Techsoft Centre

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