netdev - [PATCH 2/2] xen-netfront: call netif_carrier

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 2 Jul 2014 16:09:15 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	<netdev@...r.kernel.org>
CC:	David Vrabel <david.vrabel@...rix.com>,
	<xen-devel@...ts.xenproject.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: [PATCH 2/2] 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 <david.vrabel@...rix.com>
---
 drivers/net/xen-netfront.c |   11 ++++-------
 1 file changed, 4 insertions(+), 7 deletions(-)

diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
index 6a37d62..055222b 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);
-- 
1.7.10.4

--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html