sata_mv: fix MSI irq race condition

Fix a (rare) race condition in mv_interrupt() when using MSI.

The value of hpriv->main_irq_mask_addr can change on on the fly,
and without this patch we could end up writing back a stale copy
to the hardware.

Signed-off-by: Mark Lord <mlord@pobox.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

diff --git a/drivers/ata/sata_mv.c b/drivers/ata/sata_mv.c
index 7007edd..74b1080 100644 (file)
--- a/drivers/ata/sata_mv.c
+++ b/drivers/ata/sata_mv.c
@@ -2218,12 +2218,13 @@ static irqreturn_t mv_interrupt(int irq, void *dev_instance)
                else
                        handled = mv_host_intr(host, pending_irqs);
        }
-       spin_unlock(&host->lock);
 
        /* for MSI: unmask; interrupt cause bits will retrigger now */
        if (using_msi)
                writel(hpriv->main_irq_mask, hpriv->main_irq_mask_addr);
 
+       spin_unlock(&host->lock);
+
        return IRQ_RETVAL(handled);
 }