On Fri, 8 May 2009, Andrew Morton wrote:

On Fri,  8 May 2009 16:01:13 +0200
Geert Uytterhoeven [off-list ref] wrote:

quoted

+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;

                ^^^^^^^^

quoted

+	}
+
+	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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