ieee1394: eth1394: handle tlabel exhaustion

When eth1394 was unable to acquire a transaction label, it just dropped
outgoing packets without attempt to resend them later.

The transmit queue is now halted if no tlabel is available to
->hard_start_xmit().  A workqueue job is then scheduled to catch the
moment when ieee1394 recycled the next lot of tlabels.

Fixes http://bugzilla.kernel.org/show_bug.cgi?id=8402

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>

2 files changed, 67 insertions, 17 deletions

diff --git a/drivers/ieee1394/eth1394.c b/drivers/ieee1394/eth1394.c
index 8e4c959e586..d6b19c2780a 100644
--- a/drivers/ieee1394/eth1394.c
+++ b/drivers/ieee1394/eth1394.c
@@ -47,6 +47,7 @@
 #include <linux/types.h>
 #include <linux/delay.h>
 #include <linux/init.h>
+#include <linux/workqueue.h>
 
 #include <linux/netdevice.h>
 #include <linux/inetdevice.h>
@@ -235,6 +236,9 @@ static int ether1394_open(struct net_device *dev)
 /* This is called after an "ifdown" */
 static int ether1394_stop(struct net_device *dev)
 {
+        /* flush priv->wake */
+        flush_scheduled_work();
+
         netif_stop_queue(dev);
         return 0;
 }
@@ -531,6 +535,37 @@ static void ether1394_init_dev(struct net_device *dev)
 }
 
 /*
+ * Wake the queue up after commonly encountered transmit failure conditions are
+ * hopefully over.  Currently only tlabel exhaustion is accounted for.
+ */
+static void ether1394_wake_queue(struct work_struct *work)
+{
+        struct eth1394_priv *priv;
+        struct hpsb_packet *packet;
+
+        priv = container_of(work, struct eth1394_priv, wake);
+        packet = hpsb_alloc_packet(0);
+
+        /* This is really bad, but unjam the queue anyway. */
+        if (!packet)
+                goto out;
+
+        packet->host = priv->host;
+        packet->node_id = priv->wake_node;
+        /*
+         * A transaction label is all we really want.  If we get one, it almost
+         * always means we can get a lot more because the ieee1394 core recycled
+         * a whole batch of tlabels, at last.
+         */
+        if (hpsb_get_tlabel(packet) == 0)
+                hpsb_free_tlabel(packet);
+
+        hpsb_free_packet(packet);
+out:
+        netif_wake_queue(priv->wake_dev);
+}
+
+/*
  * This function is called every time a card is found. It is generally called
  * when the module is installed. This is where we add all of our ethernet
  * devices. One for each host.
@@ -574,6 +609,8 @@ static void ether1394_add_host(struct hpsb_host *host)
         spin_lock_init(&priv->lock);
         priv->host = host;
         priv->local_fifo = fifo_addr;
+        INIT_WORK(&priv->wake, ether1394_wake_queue);
+        priv->wake_dev = dev;
 
         hi = hpsb_create_hostinfo(&eth1394_highlevel, host, sizeof(*hi));
         if (hi == NULL) {
@@ -1390,22 +1427,17 @@ static int ether1394_prep_write_packet(struct hpsb_packet *p,
                                        u64 addr, void *data, int tx_len)
 {
         p->node_id = node;
-        p->data = NULL;
 
-        p->tcode = TCODE_WRITEB;
-        p->header[1] = host->node_id << 16 | addr >> 32;
-        p->header[2] = addr & 0xffffffff;
+        if (hpsb_get_tlabel(p))
+                return -EAGAIN;
 
+        p->tcode = TCODE_WRITEB;
         p->header_size = 16;
         p->expect_response = 1;
-
-        if (hpsb_get_tlabel(p)) {
-                ETH1394_PRINT_G(KERN_ERR, "Out of tlabels\n");
-                return -1;
-        }
         p->header[0] =
                 p->node_id << 16 | p->tlabel << 10 | 1 << 8 | TCODE_WRITEB << 4;
-
+        p->header[1] = host->node_id << 16 | addr >> 32;
+        p->header[2] = addr & 0xffffffff;
         p->header[3] = tx_len << 16;
         p->data_size = (tx_len + 3) & ~3;
         p->data = data;
@@ -1451,7 +1483,7 @@ static int ether1394_send_packet(struct packet_task *ptask, unsigned int tx_len)
 
         packet = ether1394_alloc_common_packet(priv->host);
         if (!packet)
-                return -1;
+                return -ENOMEM;
 
         if (ptask->tx_type == ETH1394_GASP) {
                 int length = tx_len + 2 * sizeof(quadlet_t);
@@ -1462,7 +1494,7 @@ static int ether1394_send_packet(struct packet_task *ptask, unsigned int tx_len)
                                                ptask->addr, ptask->skb->data,
                                                tx_len)) {
                 hpsb_free_packet(packet);
-                return -1;
+                return -EAGAIN;
         }
 
         ptask->packet = packet;
@@ -1471,7 +1503,7 @@ static int ether1394_send_packet(struct packet_task *ptask, unsigned int tx_len)
 
         if (hpsb_send_packet(packet) < 0) {
                 ether1394_free_packet(packet);
-                return -1;
+                return -EIO;
         }
 
         return 0;
@@ -1514,13 +1546,18 @@ static void ether1394_complete_cb(void *__ptask)
 
         ptask->outstanding_pkts--;
         if (ptask->outstanding_pkts > 0 && !fail) {
-                int tx_len;
+                int tx_len, err;
 
                 /* Add the encapsulation header to the fragment */
                 tx_len = ether1394_encapsulate(ptask->skb, ptask->max_payload,
                                                &ptask->hdr);
-                if (ether1394_send_packet(ptask, tx_len))
+                err = ether1394_send_packet(ptask, tx_len);
+                if (err) {
+                        if (err == -EAGAIN)
+                                ETH1394_PRINT_G(KERN_ERR, "Out of tlabels\n");
+
                         ether1394_dg_complete(ptask, 1);
+                }
         } else {
                 ether1394_dg_complete(ptask, fail);
         }
@@ -1633,8 +1670,17 @@ static int ether1394_tx(struct sk_buff *skb, struct net_device *dev)
         /* Add the encapsulation header to the fragment */
         tx_len = ether1394_encapsulate(skb, max_payload, &ptask->hdr);
         dev->trans_start = jiffies;
-        if (ether1394_send_packet(ptask, tx_len))
-                goto fail;
+        if (ether1394_send_packet(ptask, tx_len)) {
+                if (dest_node == (LOCAL_BUS | ALL_NODES))
+                        goto fail;
+
+                /* Most failures of ether1394_send_packet are recoverable. */
+                netif_stop_queue(dev);
+                priv->wake_node = dest_node;
+                schedule_work(&priv->wake);
+                kmem_cache_free(packet_task_cache, ptask);
+                return NETDEV_TX_BUSY;
+        }
 
         return NETDEV_TX_OK;
 fail:
diff --git a/drivers/ieee1394/eth1394.h b/drivers/ieee1394/eth1394.h
index a3439ee7cb4..4f3e2dd46f0 100644
--- a/drivers/ieee1394/eth1394.h
+++ b/drivers/ieee1394/eth1394.h
@@ -66,6 +66,10 @@ struct eth1394_priv {
         int bc_dgl;                     /* Outgoing broadcast datagram label */
         struct list_head ip_node_list;  /* List of IP capable nodes      */
         struct unit_directory *ud_list[ALL_NODES]; /* Cached unit dir list */
+
+        struct work_struct wake;        /* Wake up after xmit failure    */
+        struct net_device *wake_dev;    /* Stupid backlink for .wake     */
+        nodeid_t wake_node;             /* Destination of failed xmit    */
 };