From f50b407653f64e76d1c9abda61d0d85cde3ca9ca Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Wed, 2 Jul 2014 16:09:14 +0100 Subject: xen-netfront: don't nest queue locks in xennet_connect() The nesting of the per-queue rx_lock and tx_lock in xennet_connect() is confusing to both humans and lockdep. The locking is safe because this is the only place where the locks are nested in this way but lockdep still warns. Instead of adding the missing lockdep annotations, refactor the locking to avoid the confusing nesting. This is still safe, because the xenbus connection state changes are all serialized by the xenwatch thread. Signed-off-by: David Vrabel Reported-by: Sander Eikelenboom Signed-off-by: David S. Miller --- drivers/net/xen-netfront.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) (limited to 'drivers/net/xen-netfront.c') diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index 2ccb4a02368..6a37d62de40 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -2046,13 +2046,15 @@ static int xennet_connect(struct net_device *dev) /* By now, the queue structures have been set up */ for (j = 0; j < num_queues; ++j) { queue = &np->queues[j]; - spin_lock_bh(&queue->rx_lock); - spin_lock_irq(&queue->tx_lock); /* Step 1: Discard all pending TX packet fragments. */ + spin_lock_irq(&queue->tx_lock); xennet_release_tx_bufs(queue); + spin_unlock_irq(&queue->tx_lock); /* Step 2: Rebuild the RX buffer freelist and the RX ring itself. */ + spin_lock_bh(&queue->rx_lock); + for (requeue_idx = 0, i = 0; i < NET_RX_RING_SIZE; i++) { skb_frag_t *frag; const struct page *page; @@ -2076,6 +2078,8 @@ static int xennet_connect(struct net_device *dev) } queue->rx.req_prod_pvt = requeue_idx; + + spin_unlock_bh(&queue->rx_lock); } /* @@ -2087,13 +2091,17 @@ static int xennet_connect(struct net_device *dev) netif_carrier_on(np->netdev); for (j = 0; j < num_queues; ++j) { queue = &np->queues[j]; + notify_remote_via_irq(queue->tx_irq); if (queue->tx_irq != queue->rx_irq) notify_remote_via_irq(queue->rx_irq); - xennet_tx_buf_gc(queue); - xennet_alloc_rx_buffers(queue); + spin_lock_irq(&queue->tx_lock); + xennet_tx_buf_gc(queue); spin_unlock_irq(&queue->tx_lock); + + spin_lock_bh(&queue->rx_lock); + xennet_alloc_rx_buffers(queue); spin_unlock_bh(&queue->rx_lock); } -- cgit v1.2.3-70-g09d2 From f9feb1e6a25f9e197f9e6e6cb04bf04d2cccff93 Mon Sep 17 00:00:00 2001 From: David Vrabel Date: Wed, 2 Jul 2014 16:09:15 +0100 Subject: xen-netfront: call netif_carrier_off() only once when disconnecting In xennet_disconnect_backend(), netif_carrier_off() was called once per queue when it needs to only be called once. The queue locking around the netif_carrier_off() call looked very odd. I think they were supposed to synchronize any NAPI instances with the expectation that no further NAPI instances would be scheduled because of the carrier being off (see the check in xennet_rx_interrupt()). But I can't easily tell if this works correctly. Instead, add a napi_synchronize() call after disabling the interrupts. This is obviously correct as with no Rx interrupts, no further NAPI instances will be scheduled. Signed-off-by: David Vrabel Signed-off-by: David S. Miller --- drivers/net/xen-netfront.c | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) (limited to 'drivers/net/xen-netfront.c') diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index 6a37d62de40..055222bae6e 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -1439,16 +1439,11 @@ static void xennet_disconnect_backend(struct netfront_info *info) unsigned int i = 0; unsigned int num_queues = info->netdev->real_num_tx_queues; + netif_carrier_off(info->netdev); + for (i = 0; i < num_queues; ++i) { struct netfront_queue *queue = &info->queues[i]; - /* Stop old i/f to prevent errors whilst we rebuild the state. */ - spin_lock_bh(&queue->rx_lock); - spin_lock_irq(&queue->tx_lock); - netif_carrier_off(queue->info->netdev); - spin_unlock_irq(&queue->tx_lock); - spin_unlock_bh(&queue->rx_lock); - if (queue->tx_irq && (queue->tx_irq == queue->rx_irq)) unbind_from_irqhandler(queue->tx_irq, queue); if (queue->tx_irq && (queue->tx_irq != queue->rx_irq)) { @@ -1458,6 +1453,8 @@ static void xennet_disconnect_backend(struct netfront_info *info) queue->tx_evtchn = queue->rx_evtchn = 0; queue->tx_irq = queue->rx_irq = 0; + napi_synchronize(&queue->napi); + /* End access and free the pages */ xennet_end_access(queue->tx_ring_ref, queue->tx.sring); xennet_end_access(queue->rx_ring_ref, queue->rx.sring); -- cgit v1.2.3-70-g09d2