Fix long standing panic with regards to descriptors and locking. Signed-off-by: Steven J. Hill <[EMAIL PROTECTED]> ---
diff -ur linux-2.6.22.1/drivers/net/mv643xx_eth.c linux-2.6.22.1-rci/drivers/net/mv643xx_eth.c
--- linux-2.6.22.1/drivers/net/mv643xx_eth.c 2007-07-18 22:55:11.000000000 -0500
+++ linux-2.6.22.1-rci/drivers/net/mv643xx_eth.c 2007-07-18 22:39:37.000000000 -0500
@@ -350,13 +350,6 @@
while (mp->tx_desc_count > 0) {
spin_lock_irqsave(&mp->lock, flags);
-
- /* tx_desc_count might have changed before acquiring the lock */
- if (mp->tx_desc_count <= 0) {
- spin_unlock_irqrestore(&mp->lock, flags);
- return released;
- }
-
tx_index = mp->tx_used_desc_q;
desc = &mp->p_tx_desc_area[tx_index];
#ifdef CONFIG_GT64260
@@ -367,7 +360,7 @@
if (!force && (cmd_sts & ETH_BUFFER_OWNED_BY_DMA)) {
spin_unlock_irqrestore(&mp->lock, flags);
- return released;
+ continue;
}
mp->tx_used_desc_q = (tx_index + 1) % mp->tx_ring_size;
@@ -1488,7 +1481,19 @@
BUG_ON(netif_queue_stopped(dev));
BUG_ON(skb == NULL);
- if (mp->tx_ring_size - mp->tx_desc_count < MAX_DESCS_PER_SKB) {
+ if (mp->tx_ring_size - mp->tx_desc_count <= MAX_DESCS_PER_SKB) {
+ /*
+ * We are completely out of TX descriptors, however,
+ * if 'tx_used_desc_q' is zero, most likely the port
+ * has been configured and is up, but there is no link.
+ * We attempt to free a single descriptor to keep the
+ * 'sendto' call and rest of the stack happy. If this
+ * check is taken out, expect an error and kernel panic
+ * from 'kernel/softirq.c:141' inside 'local_bh_enable'.
+ */
+ if (mp->tx_used_desc_q == 0)
+ mv643xx_eth_free_all_tx_descs(dev);
+
printk(KERN_ERR "%s: transmit with queue full\n", dev->name);
netif_stop_queue(dev);
return 1;
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