drivers-net-fix-livelock-issues.patch

From 4a633714d8cd36f73f45d21968e3cd32ec1cf204 Mon Sep 17 00:00:00 2001
From: Thomas Gleixner <tglx@linutronix.de>
Date: Sat, 20 Jun 2009 11:36:54 +0200
Subject: [PATCH] drivers/net: fix livelock issues

commit 6c37c1b53945ccc8aa55e1eac48bed3ef89bbde4 in tip.

Preempt-RT runs into a live lock issue with the NETDEV_TX_LOCKED micro
optimization. The reason is that the softirq thread is rescheduling
itself on that return value. Depending on priorities it starts to
monoplize the CPU and livelock on UP systems.

Remove it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/drivers/net/atl1c/atl1c_main.c b/drivers/net/atl1c/atl1c_main.c
index 2f4be59..5b44d14 100644
--- a/drivers/net/atl1c/atl1c_main.c
+++ b/drivers/net/atl1c/atl1c_main.c
@@ -2064,11 +2064,8 @@ static netdev_tx_t atl1c_xmit_frame(struct sk_buff *skb,
 	}
 
 	tpd_req = atl1c_cal_tpd_req(skb);
-	if (!spin_trylock_irqsave(&adapter->tx_lock, flags)) {
-		if (netif_msg_pktdata(adapter))
-			dev_info(&adapter->pdev->dev, "tx locked\n");
-		return NETDEV_TX_LOCKED;
-	}
+	spin_lock_irqsave(&adapter->tx_lock, flags);
+
 	if (skb->mark == 0x01)
 		type = atl1c_trans_high;
 	else
diff --git a/drivers/net/atl1e/atl1e_main.c b/drivers/net/atl1e/atl1e_main.c
index 08f8c09..5df9cfd 100644
--- a/drivers/net/atl1e/atl1e_main.c
+++ b/drivers/net/atl1e/atl1e_main.c
@@ -1823,8 +1823,7 @@ static netdev_tx_t atl1e_xmit_frame(struct sk_buff *skb,
 		return NETDEV_TX_OK;
 	}
 	tpd_req = atl1e_cal_tdp_req(skb);
-	if (!spin_trylock_irqsave(&adapter->tx_lock, flags))
-		return NETDEV_TX_LOCKED;
+	spin_lock_irqsave(&adapter->tx_lock, flags);
 
 	if (atl1e_tpd_avail(adapter) < tpd_req) {
 		/* no enough descriptor, just stop queue */
diff --git a/drivers/net/chelsio/sge.c b/drivers/net/chelsio/sge.c
index 109d278..abd372a 100644
--- a/drivers/net/chelsio/sge.c
+++ b/drivers/net/chelsio/sge.c
@@ -1671,8 +1671,7 @@ static int t1_sge_tx(struct sk_buff *skb, struct adapter *adapter,
 	struct cmdQ *q = &sge->cmdQ[qid];
 	unsigned int credits, pidx, genbit, count, use_sched_skb = 0;
 
-	if (!spin_trylock(&q->lock))
-		return NETDEV_TX_LOCKED;
+	spin_lock(&q->lock);
 
 	reclaim_completed_tx(sge, q);
 
diff --git a/drivers/net/rionet.c b/drivers/net/rionet.c
index ede937e..53345da 100644
--- a/drivers/net/rionet.c
+++ b/drivers/net/rionet.c
@@ -175,11 +175,7 @@ static int rionet_start_xmit(struct sk_buff *skb, struct net_device *ndev)
 	u16 destid;
 	unsigned long flags;
 
-	local_irq_save(flags);
-	if (!spin_trylock(&rnet->tx_lock)) {
-		local_irq_restore(flags);
-		return NETDEV_TX_LOCKED;
-	}
+	spin_lock_irqsave(&rnet->tx_lock, flags);
 
 	if ((rnet->tx_cnt + 1) > RIONET_TX_RING_SIZE) {
 		netif_stop_queue(ndev);
diff --git a/drivers/net/s2io.c b/drivers/net/s2io.c
index 3c4836d..9984903 100644
--- a/drivers/net/s2io.c
+++ b/drivers/net/s2io.c
@@ -4146,12 +4146,7 @@ static netdev_tx_t s2io_xmit(struct sk_buff *skb, struct net_device *dev)
 			[skb->priority & (MAX_TX_FIFOS - 1)];
 	fifo = &mac_control->fifos[queue];
 
-	if (do_spin_lock)
-		spin_lock_irqsave(&fifo->tx_lock, flags);
-	else {
-		if (unlikely(!spin_trylock_irqsave(&fifo->tx_lock, flags)))
-			return NETDEV_TX_LOCKED;
-	}
+	spin_lock_irqsave(&fifo->tx_lock, flags);
 
 	if (sp->config.multiq) {
 		if (__netif_subqueue_stopped(dev, fifo->fifo_no)) {
diff --git a/drivers/net/sungem.c b/drivers/net/sungem.c
index b571a1b..c3a1180 100644
--- a/drivers/net/sungem.c
+++ b/drivers/net/sungem.c
@@ -1034,10 +1034,8 @@ static netdev_tx_t gem_start_xmit(struct sk_buff *skb,
 			(csum_stuff_off << 21));
 	}
 
-	if (!spin_trylock_irqsave(&gp->tx_lock, flags)) {
-		/* Tell upper layer to requeue */
-		return NETDEV_TX_LOCKED;
-	}
+	spin_lock_irqsave(&gp->tx_lock, flags);
+
 	/* We raced with gem_do_stop() */
 	if (!gp->running) {
 		spin_unlock_irqrestore(&gp->tx_lock, flags);
diff --git a/drivers/net/tehuti.c b/drivers/net/tehuti.c
index 80b404f..1013891 100644
--- a/drivers/net/tehuti.c
+++ b/drivers/net/tehuti.c
@@ -1639,13 +1639,8 @@ static netdev_tx_t bdx_tx_transmit(struct sk_buff *skb,
 	unsigned long flags;
 
 	ENTER;
-	local_irq_save(flags);
-	if (!spin_trylock(&priv->tx_lock)) {
-		local_irq_restore(flags);
-		DBG("%s[%s]: TX locked, returning NETDEV_TX_LOCKED\n",
-		    BDX_DRV_NAME, ndev->name);
-		return NETDEV_TX_LOCKED;
-	}
+
+	spin_lock_irqsave(&priv->tx_lock, flags);
 
 	/* build tx descriptor */
 	BDX_ASSERT(f->m.wptr >= f->m.memsz);	/* started with valid wptr */
-- 
1.7.1.1