--- old/drivers/ata/sata_mv.c	2011-04-13 11:03:07.442481426 -0400
+++ linux/drivers/ata/sata_mv.c	2011-04-13 11:07:55.224249621 -0400
@@ -1027,15 +1027,19 @@
 static void mv_set_main_irq_mask(struct ata_host *host,
 				 u32 disable_bits, u32 enable_bits)
 {
+	static spinlock_t irq_mask_lock = __SPIN_LOCK_UNLOCKED(irq_mask_lock); // FIXME: per-host would be nicer
 	struct mv_host_priv *hpriv = host->private_data;
 	u32 old_mask, new_mask;
+	unsigned long flags;
 
+	spin_lock_irqsave(&irq_mask_lock, flags);
 	old_mask = hpriv->main_irq_mask;
 	new_mask = (old_mask & ~disable_bits) | enable_bits;
 	if (new_mask != old_mask) {
 		hpriv->main_irq_mask = new_mask;
 		mv_write_main_irq_mask(new_mask, hpriv);
 	}
+	spin_unlock_irqrestore(&irq_mask_lock, flags);
 }
 
 static void mv_enable_port_irqs(struct ata_port *ap,