IPoIB: Use netif_tx_lock() and get rid of private tx_lock, LLTX

Currently, IPoIB is an LLTX driver that uses its own IRQ-disabling
tx_lock.  Not only do we want to get rid of LLTX, this actually causes
problems because of the skb_orphan() done with this tx_lock held: some
skb destructors expect to be run with interrupts enabled.

The simplest fix for this is to get rid of the driver-private tx_lock
and stop using LLTX.  We kill off priv->tx_lock and use
netif_tx_lock[_bh]() instead; the patch to do this is a tiny bit
tricky because we need to update places that take priv->lock inside
the tx_lock to disable IRQs, rather than relying on tx_lock having
already disabled IRQs.

Also, there are a couple of places where we need to disable BHs to
make sure we have a consistent context to call netif_tx_lock() (since
we no longer can use _irqsave() variants), and we also have to change
ipoib_send_comp_handler() to call drain_tx_cq() through a timer rather
than directly, because ipoib_send_comp_handler() runs in interrupt
context and drain_tx_cq() must run in BH context so it can call
netif_tx_lock().

Signed-off-by: Roland Dreier <rolandd@cisco.com>

drivers/infiniband/ulp/ipoib/ipoib.h

@@ -268,10 +268,9 @@ struct ipoib_lro {
 };
 
 /*
- * Device private locking: tx_lock protects members used in TX fast
- * path (and we use LLTX so upper layers don't do extra locking).
- * lock protects everything else.  lock nests inside of tx_lock (ie
- * tx_lock must be acquired first if needed).
+ * Device private locking: network stack tx_lock protects members used
+ * in TX fast path, lock protects everything else.  lock nests inside
+ * of tx_lock (ie tx_lock must be acquired first if needed).
  */
 struct ipoib_dev_priv {
 	spinlock_t lock;
@@ -320,7 +319,6 @@ struct ipoib_dev_priv {
 
 	struct ipoib_rx_buf *rx_ring;
 
-	spinlock_t	     tx_lock;
 	struct ipoib_tx_buf *tx_ring;
 	unsigned	     tx_head;
 	unsigned	     tx_tail;

drivers/infiniband/ulp/ipoib/ipoib_cm.c

@@ -786,7 +786,8 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
 
 	dev_kfree_skb_any(tx_req->skb);
 
-	spin_lock_irqsave(&priv->tx_lock, flags);
+	netif_tx_lock(dev);
+
 	++tx->tx_tail;
 	if (unlikely(--priv->tx_outstanding == ipoib_sendq_size >> 1) &&
 	    netif_queue_stopped(dev) &&
@@ -801,7 +802,7 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
 			   "(status=%d, wrid=%d vend_err %x)\n",
 			   wc->status, wr_id, wc->vendor_err);
 
-		spin_lock(&priv->lock);
+		spin_lock_irqsave(&priv->lock, flags);
 		neigh = tx->neigh;
 
 		if (neigh) {
@@ -821,10 +822,10 @@ void ipoib_cm_handle_tx_wc(struct net_device *dev, struct ib_wc *wc)
 
 		clear_bit(IPOIB_FLAG_OPER_UP, &tx->flags);
 
-		spin_unlock(&priv->lock);
+		spin_unlock_irqrestore(&priv->lock, flags);
 	}
 
-	spin_unlock_irqrestore(&priv->tx_lock, flags);
+	netif_tx_unlock(dev);
 }
 
 int ipoib_cm_dev_open(struct net_device *dev)
@@ -1149,7 +1150,6 @@ static void ipoib_cm_tx_destroy(struct ipoib_cm_tx *p)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(p->dev);
 	struct ipoib_cm_tx_buf *tx_req;
-	unsigned long flags;
 	unsigned long begin;
 
 	ipoib_dbg(priv, "Destroy active connection 0x%x head 0x%x tail 0x%x\n",
@@ -1180,12 +1180,12 @@ static void ipoib_cm_tx_destroy(struct ipoib_cm_tx *p)
 				    DMA_TO_DEVICE);
 		dev_kfree_skb_any(tx_req->skb);
 		++p->tx_tail;
-		spin_lock_irqsave(&priv->tx_lock, flags);
+		netif_tx_lock_bh(p->dev);
 		if (unlikely(--priv->tx_outstanding == ipoib_sendq_size >> 1) &&
 		    netif_queue_stopped(p->dev) &&
 		    test_bit(IPOIB_FLAG_ADMIN_UP, &priv->flags))
 			netif_wake_queue(p->dev);
-		spin_unlock_irqrestore(&priv->tx_lock, flags);
+		netif_tx_unlock_bh(p->dev);
 	}
 
 	if (p->qp)
@@ -1202,6 +1202,7 @@ static int ipoib_cm_tx_handler(struct ib_cm_id *cm_id,
 	struct ipoib_dev_priv *priv = netdev_priv(tx->dev);
 	struct net_device *dev = priv->dev;
 	struct ipoib_neigh *neigh;
+	unsigned long flags;
 	int ret;
 
 	switch (event->event) {
@@ -1220,8 +1221,8 @@ static int ipoib_cm_tx_handler(struct ib_cm_id *cm_id,
 	case IB_CM_REJ_RECEIVED:
 	case IB_CM_TIMEWAIT_EXIT:
 		ipoib_dbg(priv, "CM error %d.\n", event->event);
-		spin_lock_irq(&priv->tx_lock);
-		spin_lock(&priv->lock);
+		netif_tx_lock_bh(dev);
+		spin_lock_irqsave(&priv->lock, flags);
 		neigh = tx->neigh;
 
 		if (neigh) {
@@ -1239,8 +1240,8 @@ static int ipoib_cm_tx_handler(struct ib_cm_id *cm_id,
 			queue_work(ipoib_workqueue, &priv->cm.reap_task);
 		}
 
-		spin_unlock(&priv->lock);
-		spin_unlock_irq(&priv->tx_lock);
+		spin_unlock_irqrestore(&priv->lock, flags);
+		netif_tx_unlock_bh(dev);
 		break;
 	default:
 		break;
@@ -1294,19 +1295,24 @@ static void ipoib_cm_tx_start(struct work_struct *work)
 	struct ib_sa_path_rec pathrec;
 	u32 qpn;
 
-	spin_lock_irqsave(&priv->tx_lock, flags);
-	spin_lock(&priv->lock);
+	netif_tx_lock_bh(dev);
+	spin_lock_irqsave(&priv->lock, flags);
+
 	while (!list_empty(&priv->cm.start_list)) {
 		p = list_entry(priv->cm.start_list.next, typeof(*p), list);
 		list_del_init(&p->list);
 		neigh = p->neigh;
 		qpn = IPOIB_QPN(neigh->neighbour->ha);
 		memcpy(&pathrec, &p->path->pathrec, sizeof pathrec);
-		spin_unlock(&priv->lock);
-		spin_unlock_irqrestore(&priv->tx_lock, flags);
+
+		spin_unlock_irqrestore(&priv->lock, flags);
+		netif_tx_unlock_bh(dev);
+
 		ret = ipoib_cm_tx_init(p, qpn, &pathrec);
-		spin_lock_irqsave(&priv->tx_lock, flags);
-		spin_lock(&priv->lock);
+
+		netif_tx_lock_bh(dev);
+		spin_lock_irqsave(&priv->lock, flags);
+
 		if (ret) {
 			neigh = p->neigh;
 			if (neigh) {
@@ -1320,56 +1326,66 @@ static void ipoib_cm_tx_start(struct work_struct *work)
 			kfree(p);
 		}
 	}
-	spin_unlock(&priv->lock);
-	spin_unlock_irqrestore(&priv->tx_lock, flags);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+	netif_tx_unlock_bh(dev);
 }
 
 static void ipoib_cm_tx_reap(struct work_struct *work)
 {
 	struct ipoib_dev_priv *priv = container_of(work, struct ipoib_dev_priv,
 						   cm.reap_task);
+	struct net_device *dev = priv->dev;
 	struct ipoib_cm_tx *p;
+	unsigned long flags;
+
+	netif_tx_lock_bh(dev);
+	spin_lock_irqsave(&priv->lock, flags);
 
-	spin_lock_irq(&priv->tx_lock);
-	spin_lock(&priv->lock);
 	while (!list_empty(&priv->cm.reap_list)) {
 		p = list_entry(priv->cm.reap_list.next, typeof(*p), list);
 		list_del(&p->list);
-		spin_unlock(&priv->lock);
-		spin_unlock_irq(&priv->tx_lock);
+		spin_unlock_irqrestore(&priv->lock, flags);
+		netif_tx_unlock_bh(dev);
 		ipoib_cm_tx_destroy(p);
-		spin_lock_irq(&priv->tx_lock);
-		spin_lock(&priv->lock);
+		netif_tx_lock_bh(dev);
+		spin_lock_irqsave(&priv->lock, flags);
 	}
-	spin_unlock(&priv->lock);
-	spin_unlock_irq(&priv->tx_lock);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+	netif_tx_unlock_bh(dev);
 }
 
 static void ipoib_cm_skb_reap(struct work_struct *work)
 {
 	struct ipoib_dev_priv *priv = container_of(work, struct ipoib_dev_priv,
 						   cm.skb_task);
+	struct net_device *dev = priv->dev;
 	struct sk_buff *skb;
-
+	unsigned long flags;
 	unsigned mtu = priv->mcast_mtu;
 
-	spin_lock_irq(&priv->tx_lock);
-	spin_lock(&priv->lock);
+	netif_tx_lock_bh(dev);
+	spin_lock_irqsave(&priv->lock, flags);
+
 	while ((skb = skb_dequeue(&priv->cm.skb_queue))) {
-		spin_unlock(&priv->lock);
-		spin_unlock_irq(&priv->tx_lock);
+		spin_unlock_irqrestore(&priv->lock, flags);
+		netif_tx_unlock_bh(dev);
+
 		if (skb->protocol == htons(ETH_P_IP))
 			icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 		else if (skb->protocol == htons(ETH_P_IPV6))
 			icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu, priv->dev);
 #endif
 		dev_kfree_skb_any(skb);
-		spin_lock_irq(&priv->tx_lock);
-		spin_lock(&priv->lock);
+
+		netif_tx_lock_bh(dev);
+		spin_lock_irqsave(&priv->lock, flags);
 	}
-	spin_unlock(&priv->lock);
-	spin_unlock_irq(&priv->tx_lock);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+	netif_tx_unlock_bh(dev);
 }
 
 void ipoib_cm_skb_too_long(struct net_device *dev, struct sk_buff *skb,

drivers/infiniband/ulp/ipoib/ipoib_ib.c

@@ -468,21 +468,22 @@ void ipoib_ib_completion(struct ib_cq *cq, void *dev_ptr)
 static void drain_tx_cq(struct net_device *dev)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
-	unsigned long flags;
 
-	spin_lock_irqsave(&priv->tx_lock, flags);
+	netif_tx_lock(dev);
 	while (poll_tx(priv))
 		; /* nothing */
 
 	if (netif_queue_stopped(dev))
 		mod_timer(&priv->poll_timer, jiffies + 1);
 
-	spin_unlock_irqrestore(&priv->tx_lock, flags);
+	netif_tx_unlock(dev);
 }
 
 void ipoib_send_comp_handler(struct ib_cq *cq, void *dev_ptr)
 {
-	drain_tx_cq((struct net_device *)dev_ptr);
+	struct ipoib_dev_priv *priv = netdev_priv(dev_ptr);
+
+	mod_timer(&priv->poll_timer, jiffies);
 }
 
 static inline int post_send(struct ipoib_dev_priv *priv,
@@ -614,17 +615,20 @@ static void __ipoib_reap_ah(struct net_device *dev)
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 	struct ipoib_ah *ah, *tah;
 	LIST_HEAD(remove_list);
+	unsigned long flags;
+
+	netif_tx_lock_bh(dev);
+	spin_lock_irqsave(&priv->lock, flags);
 
-	spin_lock_irq(&priv->tx_lock);
-	spin_lock(&priv->lock);
 	list_for_each_entry_safe(ah, tah, &priv->dead_ahs, list)
 		if ((int) priv->tx_tail - (int) ah->last_send >= 0) {
 			list_del(&ah->list);
 			ib_destroy_ah(ah->ah);
 			kfree(ah);
 		}
-	spin_unlock(&priv->lock);
-	spin_unlock_irq(&priv->tx_lock);
+
+	spin_unlock_irqrestore(&priv->lock, flags);
+	netif_tx_unlock_bh(dev);
 }
 
 void ipoib_reap_ah(struct work_struct *work)
@@ -761,6 +765,14 @@ void ipoib_drain_cq(struct net_device *dev)
 {
 	struct ipoib_dev_priv *priv = netdev_priv(dev);
 	int i, n;
+
+	/*
+	 * We call completion handling routines that expect to be
+	 * called from the BH-disabled NAPI poll context, so disable
+	 * BHs here too.
+	 */
+	local_bh_disable();
+
 	do {
 		n = ib_poll_cq(priv->recv_cq, IPOIB_NUM_WC, priv->ibwc);
 		for (i = 0; i < n; ++i) {
@@ -784,6 +796,8 @@ void ipoib_drain_cq(struct net_device *dev)
 
 	while (poll_tx(priv))
 		; /* nothing */
+
+	local_bh_enable();
 }
 
 int ipoib_ib_dev_stop(struct net_device *dev, int flush)