Commit 67fa3660 authored by Paul Durrant's avatar Paul Durrant Committed by David S. Miller
Browse files

xen-netback: clear vif->task on disconnect

xenvif_start_xmit() relies on checking vif->task for NULL to determine
whether the vif is ready to accept packets. The task thread is stopped in
xenvif_disconnect() but task is not set to NULL. Thus, on a re-connect the
check will give a false positive.

Also since commit ea732dff

 (Handle backend
state transitions in a more robust way) it should not be possible for
xenvif_connect() to be called if the vif is already connected so change the
check of vif->tx_irq to a BUG_ON() and also add a BUG_ON(vif->task).

Signed-off-by: default avatarPaul Durrant <>
Cc: Wei Liu <>
Cc: Ian Campbell <>
Cc: David Vrabel <>
Acked-by: default avatarWei Liu <>
Signed-off-by: default avatarDavid S. Miller <>
parent 7ce5a27f
......@@ -368,11 +368,11 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
unsigned long rx_ring_ref, unsigned int tx_evtchn,
unsigned int rx_evtchn)
struct task_struct *task;
int err = -ENOMEM;
/* Already connected through? */
if (vif->tx_irq)
return 0;
err = xenvif_map_frontend_rings(vif, tx_ring_ref, rx_ring_ref);
if (err < 0)
......@@ -411,14 +411,16 @@ int xenvif_connect(struct xenvif *vif, unsigned long tx_ring_ref,
vif->task = kthread_create(xenvif_kthread,
(void *)vif, "%s", vif->dev->name);
if (IS_ERR(vif->task)) {
task = kthread_create(xenvif_kthread,
(void *)vif, "%s", vif->dev->name);
if (IS_ERR(task)) {
pr_warn("Could not allocate kthread for %s\n", vif->dev->name);
err = PTR_ERR(vif->task);
err = PTR_ERR(task);
goto err_rx_unbind;
vif->task = task;
if (!vif->can_sg && vif->dev->mtu > ETH_DATA_LEN)
dev_set_mtu(vif->dev, ETH_DATA_LEN);
......@@ -461,8 +463,10 @@ void xenvif_disconnect(struct xenvif *vif)
if (netif_carrier_ok(vif->dev))
if (vif->task)
if (vif->task) {
vif->task = NULL;
if (vif->tx_irq) {
if (vif->tx_irq == vif->rx_irq)
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