[PATCH net] xen-netback: move netif_napi_add before binding interrupt

[PATCH net] xen-netback: move netif_napi_add before binding interrupt

[Wei Liu]

Interrupt is enabled when bind_interdomain_evtchn_to_irqhandler returns.
If there's interrupt pending interrupt handler is invoked.

NAPI needs to be initialised before binding interrupt otherwise the
interrupt handler will try to scheduling a NAPI instance that is not
initialised yet, resulting in kernel OOPS.

This fixes a regression introduced in ea2c5e13 ("xen-netback: move NAPI
add/remove calls").

Ideally function calls to create kthreads should also be moved before
binding but I intent to fix this regression with minimal changes and
refactor the code with another patch.

Reported-by: Thomas Leonard <talex5@gmail.com>
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
---
 drivers/net/xen-netback/interface.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index e29e15d..f379689 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -576,6 +576,9 @@ int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
 	init_waitqueue_head(&queue->dealloc_wq);
 	atomic_set(&queue->inflight_packets, 0);
 
+	netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll,
+			XENVIF_NAPI_WEIGHT);
+
 	if (tx_evtchn == rx_evtchn) {
 		/* feature-split-event-channels == 0 */
 		err = bind_interdomain_evtchn_to_irqhandler(
@@ -629,9 +632,6 @@ int xenvif_connect(struct xenvif_queue *queue, unsigned long tx_ring_ref,
 	wake_up_process(queue->task);
 	wake_up_process(queue->dealloc_task);
 
-	netif_napi_add(queue->vif->dev, &queue->napi, xenvif_poll,
-			XENVIF_NAPI_WEIGHT);
-
 	return 0;
 
 err_rx_unbind:
-- 
1.7.10.4

Re: [PATCH net] xen-netback: move netif_napi_add before binding interrupt

[David Miller]

From: Wei Liu <wei.liu2@citrix.com>
Date: Mon, 25 Aug 2014 16:44:00 +0100

> Interrupt is enabled when bind_interdomain_evtchn_to_irqhandler returns.
> If there's interrupt pending interrupt handler is invoked.
> 
> NAPI needs to be initialised before binding interrupt otherwise the
> interrupt handler will try to scheduling a NAPI instance that is not
> initialised yet, resulting in kernel OOPS.
> 
> This fixes a regression introduced in ea2c5e13 ("xen-netback: move NAPI
> add/remove calls").
> 
> Ideally function calls to create kthreads should also be moved before
> binding but I intent to fix this regression with minimal changes and
> refactor the code with another patch.
> 
> Reported-by: Thomas Leonard <talex5@gmail.com>
> Signed-off-by: Wei Liu <wei.liu2@citrix.com>
> Cc: Ian Campbell <ian.campbell@citrix.com>

Applied and queued up for -stable, thanks.