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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

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@xxxxxxxxx>
Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
Cc: Ian Campbell <ian.campbell@xxxxxxxxxx>
---
 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


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