[PATCH net 1/1] via-velocity: fix netif_receive_skb use in irq disabled section.

[PATCH net 1/1] via-velocity: fix netif_receive_skb use in irq disabled section.

[Francois Romieu]

2fdac010bdcf10a30711b6924612dfc40daf19b8 ("via-velocity.c: update napi
implementation") overlooked an irq disabling spinlock when the Rx part
of the NAPI poll handler was converted from netif_rx to netif_receive_skb.

NAPI Rx processing can be taken out of the locked section with a pair of
napi_{disable / enable} since it only races with the MTU change function.

An heavier rework of the NAPI locking would be able to perform NAPI Tx
before Rx where I simply removed one of velocity_tx_srv calls.

References: https://bugzilla.redhat.com/show_bug.cgi?id=1022733
Fixes: 2fdac010bdcf (via-velocity.c: update napi implementation)
Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
Tested-by: Alex A. Schmidt <aaschmidt1@gmail.com>
Cc: Jamie Heilman <jamie@audible.transient.net>
Cc: Michele Baldessari <michele@acksyn.org>
Cc: Julia Lawall <Julia.Lawall@lip6.fr>
---

 It is relevant for stable 3.11.x and 3.12.y.

 drivers/net/ethernet/via/via-velocity.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/via/via-velocity.c b/drivers/net/ethernet/via/via-velocity.c
index d022bf9..ad61d26 100644
--- a/drivers/net/ethernet/via/via-velocity.c
+++ b/drivers/net/ethernet/via/via-velocity.c
@@ -2172,16 +2172,13 @@ static int velocity_poll(struct napi_struct *napi, int budget)
 	unsigned int rx_done;
 	unsigned long flags;
 
-	spin_lock_irqsave(&vptr->lock, flags);
 	/*
 	 * Do rx and tx twice for performance (taken from the VIA
 	 * out-of-tree driver).
 	 */
-	rx_done = velocity_rx_srv(vptr, budget / 2);
-	velocity_tx_srv(vptr);
-	rx_done += velocity_rx_srv(vptr, budget - rx_done);
+	rx_done = velocity_rx_srv(vptr, budget);
+	spin_lock_irqsave(&vptr->lock, flags);
 	velocity_tx_srv(vptr);
-
 	/* If budget not fully consumed, exit the polling mode */
 	if (rx_done < budget) {
 		napi_complete(napi);
@@ -2342,6 +2339,8 @@ static int velocity_change_mtu(struct net_device *dev, int new_mtu)
 		if (ret < 0)
 			goto out_free_tmp_vptr_1;
 
+		napi_disable(&vptr->napi);
+
 		spin_lock_irqsave(&vptr->lock, flags);
 
 		netif_stop_queue(dev);
@@ -2362,6 +2361,8 @@ static int velocity_change_mtu(struct net_device *dev, int new_mtu)
 
 		velocity_give_many_rx_descs(vptr);
 
+		napi_enable(&vptr->napi);
+
 		mac_enable_int(vptr->mac_regs);
 		netif_start_queue(dev);
 
-- 
1.8.3.1

Re: [PATCH net 1/1] via-velocity: fix netif_receive_skb use in irq disabled section.

[David Miller]

From: Francois Romieu <romieu@fr.zoreil.com>
Date: Tue, 26 Nov 2013 00:40:58 +0100

> 2fdac010bdcf10a30711b6924612dfc40daf19b8 ("via-velocity.c: update napi
> implementation") overlooked an irq disabling spinlock when the Rx part
> of the NAPI poll handler was converted from netif_rx to netif_receive_skb.
> 
> NAPI Rx processing can be taken out of the locked section with a pair of
> napi_{disable / enable} since it only races with the MTU change function.
> 
> An heavier rework of the NAPI locking would be able to perform NAPI Tx
> before Rx where I simply removed one of velocity_tx_srv calls.
> 
> References: https://bugzilla.redhat.com/show_bug.cgi?id=1022733
> Fixes: 2fdac010bdcf (via-velocity.c: update napi implementation)
> Signed-off-by: Francois Romieu <romieu@fr.zoreil.com>
> Tested-by: Alex A. Schmidt <aaschmidt1@gmail.com>

Applied and queued up for -stable, thanks.

Just a note that we usually recommend to people to do TX processing
before RX in NAPI, because the TX work can liberate packets and make
them available to RX reclaim.  But that would be quite hard with the
approach you took to fix this bug simply.