From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: [PATCH 1/2] xen-netfront: don't nest queue locks in xennet_connect() Date: Wed, 2 Jul 2014 16:09:14 +0100 Message-ID: <1404313755-27349-2-git-send-email-david.vrabel@citrix.com> References: <1404313755-27349-1-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain Cc: David Vrabel , , Konrad Rzeszutek Wilk , Boris Ostrovsky To: Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:46520 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754093AbaGBPJ0 (ORCPT ); Wed, 2 Jul 2014 11:09:26 -0400 In-Reply-To: <1404313755-27349-1-git-send-email-david.vrabel@citrix.com> Sender: netdev-owner@vger.kernel.org List-ID: 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 --- drivers/net/xen-netfront.c | 16 ++++++++++++---- 1 file changed, 12 insertions(+), 4 deletions(-) diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index 2ccb4a0..6a37d62 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); } -- 1.7.10.4