On Wed, Sep 01, 2010 at 02:42:30PM +0100, Ben Hutchings wrote:

On Wed, 2010-09-01 at 09:43 +0800, Liang Li wrote:

quoted

It's common sense that when we should do change to driver ring
desc/buffer etc only after 'stop/shutdown' the device. When we
do change while devices/driver is running, kernel oops occur:

[...]

quoted

-	ug_info->bdRingLenRx[queue] = ring->rx_pending;
-	ug_info->bdRingLenTx[queue] = ring->tx_pending;
-
 	if (netif_running(netdev)) {
-		/* FIXME: restart automatically */
-		printk(KERN_INFO
-			"Please re-open the interface.\n");
+		u16 rx_t;
+		u16 tx_t;
+		printk(KERN_INFO "Stopping interface %s.\n", netdev->name);
+		ucc_geth_close(netdev);
+
+		rx_t = ug_info->bdRingLenRx[queue];
+		tx_t = ug_info->bdRingLenTx[queue];
+
+		ug_info->bdRingLenRx[queue] = ring->rx_pending;
+		ug_info->bdRingLenTx[queue] = ring->tx_pending;
+
+		printk(KERN_INFO "Reactivating interface %s.\n", netdev->name);
+		ret = ucc_geth_open(netdev);
+		if (ret) {
+			printk(KERN_WARNING "uec_set_ringparam: set ring param for running"
+					" interface %s failed. Please try to make the interface "
+					" down, then try again.\n", netdev->name);
+			ug_info->bdRingLenRx[queue] = rx_t;
+			ug_info->bdRingLenTx[queue] = tx_t;
+		}

[...]

Bringing the interface down will call ucc_geth_close(), which will try
to free resources that have not been allocated!

Sorry, I did not understand you on this point. There is no
ucc_geth_close when 'open fail'. What you mean here exactly?

If you cannot roll back a failed change then at least use dev_close()
and dev_open() rather than calling ucc_geth_{close,open}() directly, so
that the interface state is updated correctly.  Or just refuse to make
the change if the interface is up.

That make things more simply but I do not think that is necessary.
Since there is no such restriction exist in most NIC drivers. :)
Actually I did not see the 'fail of reopen' case. So I assume you
may witnessed similar 'open fail' case in some rare cases. May you
please give more input on this then I can 'make re-open safer' here.

Thanks,
				-Liang Li

Ben.

-- 
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.