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Date: Tue, 17 Sep 2013 16:45:25 +0000
From: Paul Durrant <Paul.Durrant@...rix.com>
To: Paul Durrant <Paul.Durrant@...rix.com>,
"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
"netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC: David Vrabel <david.vrabel@...rix.com>,
Wei Liu <wei.liu2@...rix.com>,
Ian Campbell <Ian.Campbell@...rix.com>
Subject: RE: [PATCH v4] Don't destroy the netdev until the vif is shut down
> -----Original Message-----
> From: Paul Durrant [mailto:paul.durrant@...rix.com]
> Sent: 17 September 2013 16:45
> To: xen-devel@...ts.xen.org; netdev@...r.kernel.org
> Cc: Paul Durrant; David Vrabel; Wei Liu; Ian Campbell
> Subject: [PATCH v4] Don't destroy the netdev until the vif is shut down
>
Apologies for the loss of the net-next prefix here. I'll re-send with the prefix.
Paul
> Without this patch, if a frontend cycles through states Closing
> and Closed (which Windows frontends need to do) then the netdev
> will be destroyed and requires re-invocation of hotplug scripts
> to restore state before the frontend can move to Connected. Thus
> when udev is not in use the backend gets stuck in InitWait.
>
> With this patch, the netdev is left alone whilst the backend is
> still online and is only de-registered and freed just prior to
> destroying the vif (which is also nicely symmetrical with the
> netdev allocation and registration being done during probe) so
> no re-invocation of hotplug scripts is required.
>
> Signed-off-by: Paul Durrant <paul.durrant@...rix.com>
> Cc: David Vrabel <david.vrabel@...rix.com>
> Cc: Wei Liu <wei.liu2@...rix.com>
> Cc: Ian Campbell <ian.campbell@...rix.com>
> ---
> v2:
> - Modify netback_remove() - bug only seemed to manifest with linux guest
>
> v3:
> - Move __module_get() and module_put() calls
>
> v4:
> - Clear tx_irq in xenvif_disconnect() to make sure that a subsequent
> call to xenvif_connect() doesn't get nop-ed.
>
> drivers/net/xen-netback/common.h | 1 +
> drivers/net/xen-netback/interface.c | 26 ++++++++++----------------
> drivers/net/xen-netback/xenbus.c | 17 ++++++++++++-----
> 3 files changed, 23 insertions(+), 21 deletions(-)
>
> diff --git a/drivers/net/xen-netback/common.h b/drivers/net/xen-
> netback/common.h
> index a197743..5715318 100644
> --- a/drivers/net/xen-netback/common.h
> +++ b/drivers/net/xen-netback/common.h
> @@ -184,6 +184,7 @@ int xenvif_connect(struct xenvif *vif, unsigned long
> tx_ring_ref,
> unsigned long rx_ring_ref, unsigned int tx_evtchn,
> unsigned int rx_evtchn);
> void xenvif_disconnect(struct xenvif *vif);
> +void xenvif_free(struct xenvif *vif);
>
> int xenvif_xenbus_init(void);
> void xenvif_xenbus_fini(void);
> diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-
> netback/interface.c
> index 625c6f4..0465e0f 100644
> --- a/drivers/net/xen-netback/interface.c
> +++ b/drivers/net/xen-netback/interface.c
> @@ -353,6 +353,9 @@ struct xenvif *xenvif_alloc(struct device *parent,
> domid_t domid,
> }
>
> netdev_dbg(dev, "Successfully created xenvif\n");
> +
> + __module_get(THIS_MODULE);
> +
> return vif;
> }
>
> @@ -366,8 +369,6 @@ int xenvif_connect(struct xenvif *vif, unsigned long
> tx_ring_ref,
> if (vif->tx_irq)
> return 0;
>
> - __module_get(THIS_MODULE);
> -
> err = xenvif_map_frontend_rings(vif, tx_ring_ref, rx_ring_ref);
> if (err < 0)
> goto err;
> @@ -452,12 +453,6 @@ void xenvif_carrier_off(struct xenvif *vif)
>
> void xenvif_disconnect(struct xenvif *vif)
> {
> - /* Disconnect funtion might get called by generic framework
> - * even before vif connects, so we need to check if we really
> - * need to do a module_put.
> - */
> - int need_module_put = 0;
> -
> if (netif_carrier_ok(vif->dev))
> xenvif_carrier_off(vif);
>
> @@ -468,23 +463,22 @@ void xenvif_disconnect(struct xenvif *vif)
> unbind_from_irqhandler(vif->tx_irq, vif);
> unbind_from_irqhandler(vif->rx_irq, vif);
> }
> - /* vif->irq is valid, we had a module_get in
> - * xenvif_connect.
> - */
> - need_module_put = 1;
> + vif->tx_irq = 0;
> }
>
> if (vif->task)
> kthread_stop(vif->task);
>
> + xenvif_unmap_frontend_rings(vif);
> +}
> +
> +void xenvif_free(struct xenvif *vif)
> +{
> netif_napi_del(&vif->napi);
>
> unregister_netdev(vif->dev);
>
> - xenvif_unmap_frontend_rings(vif);
> -
> free_netdev(vif->dev);
>
> - if (need_module_put)
> - module_put(THIS_MODULE);
> + module_put(THIS_MODULE);
> }
> diff --git a/drivers/net/xen-netback/xenbus.c b/drivers/net/xen-
> netback/xenbus.c
> index 1fe48fe3..a53782e 100644
> --- a/drivers/net/xen-netback/xenbus.c
> +++ b/drivers/net/xen-netback/xenbus.c
> @@ -42,7 +42,7 @@ static int netback_remove(struct xenbus_device *dev)
> if (be->vif) {
> kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
> xenbus_rm(XBT_NIL, dev->nodename, "hotplug-status");
> - xenvif_disconnect(be->vif);
> + xenvif_free(be->vif);
> be->vif = NULL;
> }
> kfree(be);
> @@ -213,9 +213,18 @@ static void disconnect_backend(struct
> xenbus_device *dev)
> {
> struct backend_info *be = dev_get_drvdata(&dev->dev);
>
> + if (be->vif)
> + xenvif_disconnect(be->vif);
> +}
> +
> +static void destroy_backend(struct xenbus_device *dev)
> +{
> + struct backend_info *be = dev_get_drvdata(&dev->dev);
> +
> if (be->vif) {
> + kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
> xenbus_rm(XBT_NIL, dev->nodename, "hotplug-status");
> - xenvif_disconnect(be->vif);
> + xenvif_free(be->vif);
> be->vif = NULL;
> }
> }
> @@ -246,14 +255,11 @@ static void frontend_changed(struct xenbus_device
> *dev,
> case XenbusStateConnected:
> if (dev->state == XenbusStateConnected)
> break;
> - backend_create_xenvif(be);
> if (be->vif)
> connect(be);
> break;
>
> case XenbusStateClosing:
> - if (be->vif)
> - kobject_uevent(&dev->dev.kobj, KOBJ_OFFLINE);
> disconnect_backend(dev);
> xenbus_switch_state(dev, XenbusStateClosing);
> break;
> @@ -262,6 +268,7 @@ static void frontend_changed(struct xenbus_device
> *dev,
> xenbus_switch_state(dev, XenbusStateClosed);
> if (xenbus_dev_is_online(dev))
> break;
> + destroy_backend(dev);
> /* fall through if not online */
> case XenbusStateUnknown:
> device_unregister(&dev->dev);
> --
> 1.7.10.4
--
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