[2.6 PATCH]: Fix deadlock in driver 3c574_cs.c

[Ville Nuorvala <vnuorval@xxxxxxxxxx>]

Hello,

I already sent a report about this to linux-net earlier, but I guess it
went unnoticed due to thanksgiving...

The deadlock occurs when update_stats() is called from el3_interrupt(),
which already holds the lp->window_lock. The patch below fixes this
behavior.

Thanks,
Ville

===== drivers/net/pcmcia/3c574_cs.c 1.25 vs edited =====
--- 1.25/drivers/net/pcmcia/3c574_cs.c  Sat Sep  6 22:50:44 2003
+++ edited/drivers/net/pcmcia/3c574_cs.c        Thu Nov 27 10:26:34 2003
@@ -1092,8 +1092,12 @@
 {
        struct el3_private *lp = (struct el3_private *)dev->priv;

-       if (netif_device_present(dev))
+       if (netif_device_present(dev)) {
+               unsigned long flags;
+               spin_lock_irqsave(&lp->window_lock, flags);
                update_stats(dev);
+               spin_unlock_irqrestore(&lp->window_lock, flags);
+       }
        return &lp->stats;
 }

@@ -1105,7 +1109,6 @@
 {
        struct el3_private *lp = (struct el3_private *)dev->priv;
        ioaddr_t ioaddr = dev->base_addr;
-       unsigned long flags;
        u8 rx, tx, up;

        DEBUG(2, "%s: updating the statistics.\n", dev->name);
@@ -1113,8 +1116,6 @@
        if (inw(ioaddr+EL3_STATUS) == 0xffff) /* No card. */
                return;

-       spin_lock_irqsave(&lp->window_lock, flags);
-
        /* Unlike the 3c509 we need not turn off stats updates while reading. */
        /* Switch to the stats window, and read everything. */
        EL3WINDOW(6);
@@ -1139,7 +1140,6 @@
        lp->stats.tx_bytes                      += tx + ((up & 0xf0) << 12);

        EL3WINDOW(1);
-       spin_unlock_irqrestore(&lp->window_lock, flags);
 }

 static int el3_rx(struct net_device *dev, int worklimit)
@@ -1281,6 +1281,8 @@
        DEBUG(2, "%s: shutting down ethercard.\n", dev->name);

        if (DEV_OK(link)) {
+               unsigned long flags;
+
                /* Turn off statistics ASAP.  We update lp->stats below. */
                outw(StatsDisable, ioaddr + EL3_CMD);

@@ -1290,8 +1292,9 @@

                /* Note: Switching to window 0 may disable the IRQ. */
                EL3WINDOW(0);
-
+               spin_lock_irqsave(&lp->window_lock, flags);
                update_stats(dev);
+               spin_unlock_irqrestore(&lp->window_lock, flags);
        }

        link->open--;

--
Ville Nuorvala
Research Assistant, Institute of Digital Communications,
Helsinki University of Technology
email: vnuorval@xxxxxxxxxx, phone: +358 (0)9 451 5257