[PATCH net-next] hyperv: Move state setting for link query

[PATCH net-next] hyperv: Move state setting for link query

[Haiyang Zhang]

It moves the state setting for query into rndis_filter_receive_response().
All callbacks including query-complete and status-callback are synchronized
by channel->inbound_lock. This prevents pentential race between them.

Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
---
 drivers/net/hyperv/rndis_filter.c |   21 ++++++++++++++++++++-
 1 files changed, 20 insertions(+), 1 deletions(-)

diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
index f0cc8ef..6a9f602 100644
--- a/drivers/net/hyperv/rndis_filter.c
+++ b/drivers/net/hyperv/rndis_filter.c
@@ -240,6 +240,22 @@ static int rndis_filter_send_request(struct rndis_device *dev,
 	return ret;
 }
 
+static void rndis_set_link_state(struct rndis_device *rdev,
+				 struct rndis_request *request)
+{
+	u32 link_status;
+	struct rndis_query_complete *query_complete;
+
+	query_complete = &request->response_msg.msg.query_complete;
+
+	if (query_complete->status == RNDIS_STATUS_SUCCESS &&
+	    query_complete->info_buflen == sizeof(u32)) {
+		memcpy(&link_status, (void *)((unsigned long)query_complete +
+		       query_complete->info_buf_offset), sizeof(u32));
+		rdev->link_state = link_status != 0;
+	}
+}
+
 static void rndis_filter_receive_response(struct rndis_device *dev,
 				       struct rndis_message *resp)
 {
@@ -269,6 +285,10 @@ static void rndis_filter_receive_response(struct rndis_device *dev,
 		    sizeof(struct rndis_message) + RNDIS_EXT_LEN) {
 			memcpy(&request->response_msg, resp,
 			       resp->msg_len);
+			if (request->request_msg.ndis_msg_type ==
+			    RNDIS_MSG_QUERY && request->request_msg.msg.
+			    query_req.oid == RNDIS_OID_GEN_MEDIA_CONNECT_STATUS)
+				rndis_set_link_state(dev, request);
 		} else {
 			netdev_err(ndev,
 				"rndis response buffer overflow "
@@ -617,7 +637,6 @@ static int rndis_filter_query_device_link_status(struct rndis_device *dev)
 	ret = rndis_filter_query_device(dev,
 				      RNDIS_OID_GEN_MEDIA_CONNECT_STATUS,
 				      &link_status, &size);
-	dev->link_state = (link_status != 0) ? true : false;
 
 	return ret;
 }
-- 
1.7.4.1

Re: [PATCH net-next] hyperv: Move state setting for link query

[Jason Wang]

On 03/04/2014 07:54 AM, Haiyang Zhang wrote:
> It moves the state setting for query into rndis_filter_receive_response().
> All callbacks including query-complete and status-callback are synchronized
> by channel->inbound_lock. This prevents pentential race between them.

This still looks racy to me. The problem is workqueue is not
synchronized with those here.

Consider the following case in netvsc_link_change():

    if (rdev->link_state) {
    ... receive interrupt ...
    rndis_filter_receice_response() which changes rdev->link_state
    ...
        netif_carrier_off()
    }

And also it need to schedule a work otherwise the link status is out of
sync.
> Signed-off-by: Haiyang Zhang <haiyangz@microsoft.com>
> ---
>  drivers/net/hyperv/rndis_filter.c |   21 ++++++++++++++++++++-
>  1 files changed, 20 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/net/hyperv/rndis_filter.c b/drivers/net/hyperv/rndis_filter.c
> index f0cc8ef..6a9f602 100644
> --- a/drivers/net/hyperv/rndis_filter.c
> +++ b/drivers/net/hyperv/rndis_filter.c
> @@ -240,6 +240,22 @@ static int rndis_filter_send_request(struct rndis_device *dev,
>  	return ret;
>  }
>  
> +static void rndis_set_link_state(struct rndis_device *rdev,
> +				 struct rndis_request *request)
> +{
> +	u32 link_status;
> +	struct rndis_query_complete *query_complete;
> +
> +	query_complete = &request->response_msg.msg.query_complete;
> +
> +	if (query_complete->status == RNDIS_STATUS_SUCCESS &&
> +	    query_complete->info_buflen == sizeof(u32)) {
> +		memcpy(&link_status, (void *)((unsigned long)query_complete +
> +		       query_complete->info_buf_offset), sizeof(u32));
> +		rdev->link_state = link_status != 0;
> +	}
> +}
> +
>  static void rndis_filter_receive_response(struct rndis_device *dev,
>  				       struct rndis_message *resp)
>  {
> @@ -269,6 +285,10 @@ static void rndis_filter_receive_response(struct rndis_device *dev,
>  		    sizeof(struct rndis_message) + RNDIS_EXT_LEN) {
>  			memcpy(&request->response_msg, resp,
>  			       resp->msg_len);
> +			if (request->request_msg.ndis_msg_type ==
> +			    RNDIS_MSG_QUERY && request->request_msg.msg.
> +			    query_req.oid == RNDIS_OID_GEN_MEDIA_CONNECT_STATUS)
> +				rndis_set_link_state(dev, request);
>  		} else {
>  			netdev_err(ndev,
>  				"rndis response buffer overflow "
> @@ -617,7 +637,6 @@ static int rndis_filter_query_device_link_status(struct rndis_device *dev)
>  	ret = rndis_filter_query_device(dev,
>  				      RNDIS_OID_GEN_MEDIA_CONNECT_STATUS,
>  				      &link_status, &size);
> -	dev->link_state = (link_status != 0) ? true : false;
>  
>  	return ret;
>  }

RE: [PATCH net-next] hyperv: Move state setting for link query

[Haiyang Zhang]

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@redhat.com]
> Sent: Monday, March 3, 2014 10:10 PM
> To: Haiyang Zhang; davem@davemloft.net; netdev@vger.kernel.org
> Cc: KY Srinivasan; olaf@aepfle.de; linux-kernel@vger.kernel.org; driverdev-
> devel@linuxdriverproject.org
> Subject: Re: [PATCH net-next] hyperv: Move state setting for link query
> 
> On 03/04/2014 07:54 AM, Haiyang Zhang wrote:
> > It moves the state setting for query into rndis_filter_receive_response().
> > All callbacks including query-complete and status-callback are
> > synchronized by channel->inbound_lock. This prevents pentential race
> between them.
> 
> This still looks racy to me. The problem is workqueue is not synchronized with
> those here.
> 
> Consider the following case in netvsc_link_change():
> 
>     if (rdev->link_state) {
>     ... receive interrupt ...
>     rndis_filter_receice_response() which changes rdev->link_state
>     ...
>         netif_carrier_off()
>     }
> 
> And also it need to schedule a work otherwise the link status is out of sync.

The rndis_filter_query_device_link_status() makes the query and wait for the
complete message, including set state, before returning.

The rndis_filter_query_device_link_status() is called from rndis_filter_device_add(),
which is called from either netvsc_change_mtu() or netvsc_probe().

The change_mtu() and netvsc_link_change() are synchronized by rtnl_lock().
In netvsc_probe(), the status query & complete happens before register_netdev(), and
the netvsc_linkstatus_callback() schedules the work only after netdevice is registered.
So, there are no race in either case.

The carrier_on/off work will be scheduled when netvsc_open() is called. Then,
the status will be updated based on the latest link_state.

Thanks,
- Haiyang

Re: [PATCH net-next] hyperv: Move state setting for link query

[Jason Wang]

On 03/05/2014 12:57 AM, Haiyang Zhang wrote:
>
>> -----Original Message-----
>> From: Jason Wang [mailto:jasowang@redhat.com]
>> Sent: Monday, March 3, 2014 10:10 PM
>> To: Haiyang Zhang; davem@davemloft.net; netdev@vger.kernel.org
>> Cc: KY Srinivasan; olaf@aepfle.de; linux-kernel@vger.kernel.org; driverdev-
>> devel@linuxdriverproject.org
>> Subject: Re: [PATCH net-next] hyperv: Move state setting for link query
>>
>> On 03/04/2014 07:54 AM, Haiyang Zhang wrote:
>>> It moves the state setting for query into rndis_filter_receive_response().
>>> All callbacks including query-complete and status-callback are
>>> synchronized by channel->inbound_lock. This prevents pentential race
>> between them.
>>
>> This still looks racy to me. The problem is workqueue is not synchronized with
>> those here.
>>
>> Consider the following case in netvsc_link_change():
>>
>>     if (rdev->link_state) {
>>     ... receive interrupt ...
>>     rndis_filter_receice_response() which changes rdev->link_state
>>     ...
>>         netif_carrier_off()
>>     }
>>
>> And also it need to schedule a work otherwise the link status is out of sync.
> The rndis_filter_query_device_link_status() makes the query and wait for the
> complete message, including set state, before returning.
>
> The rndis_filter_query_device_link_status() is called from rndis_filter_device_add(),
> which is called from either netvsc_change_mtu() or netvsc_probe().
>
> The change_mtu() and netvsc_link_change() are synchronized by rtnl_lock().
> In netvsc_probe(), the status query & complete happens before register_netdev(), and
> the netvsc_linkstatus_callback() schedules the work only after netdevice is registered.
> So, there are no race in either case.
>
> The carrier_on/off work will be scheduled when netvsc_open() is called. Then,
> the status will be updated based on the latest link_state.
>
> Thanks,
> - Haiyang
>

I see. Then if the link status is changing during mtu changing in guest.
Looks like we may miss a link status updating?

RE: [PATCH net-next] hyperv: Move state setting for link query

[Haiyang Zhang]

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@redhat.com]
> Sent: Wednesday, March 5, 2014 12:57 AM
> To: Haiyang Zhang; davem@davemloft.net; netdev@vger.kernel.org
> Cc: KY Srinivasan; olaf@aepfle.de; linux-kernel@vger.kernel.org; driverdev-
> devel@linuxdriverproject.org
> Subject: Re: [PATCH net-next] hyperv: Move state setting for link query
> 
> On 03/05/2014 12:57 AM, Haiyang Zhang wrote:
> >
> >> -----Original Message-----
> >> From: Jason Wang [mailto:jasowang@redhat.com]
> >> Sent: Monday, March 3, 2014 10:10 PM
> >> To: Haiyang Zhang; davem@davemloft.net; netdev@vger.kernel.org
> >> Cc: KY Srinivasan; olaf@aepfle.de; linux-kernel@vger.kernel.org;
> >> driverdev- devel@linuxdriverproject.org
> >> Subject: Re: [PATCH net-next] hyperv: Move state setting for link
> >> query
> >>
> >> On 03/04/2014 07:54 AM, Haiyang Zhang wrote:
> >>> It moves the state setting for query into rndis_filter_receive_response().
> >>> All callbacks including query-complete and status-callback are
> >>> synchronized by channel->inbound_lock. This prevents pentential race
> >> between them.
> >>
> >> This still looks racy to me. The problem is workqueue is not
> >> synchronized with those here.
> >>
> >> Consider the following case in netvsc_link_change():
> >>
> >>     if (rdev->link_state) {
> >>     ... receive interrupt ...
> >>     rndis_filter_receice_response() which changes rdev->link_state
> >>     ...
> >>         netif_carrier_off()
> >>     }
> >>
> >> And also it need to schedule a work otherwise the link status is out of sync.
> > The rndis_filter_query_device_link_status() makes the query and wait
> > for the complete message, including set state, before returning.
> >
> > The rndis_filter_query_device_link_status() is called from
> > rndis_filter_device_add(), which is called from either netvsc_change_mtu()
> or netvsc_probe().
> >
> > The change_mtu() and netvsc_link_change() are synchronized by
> rtnl_lock().
> > In netvsc_probe(), the status query & complete happens before
> > register_netdev(), and the netvsc_linkstatus_callback() schedules the work
> only after netdevice is registered.
> > So, there are no race in either case.
> >
> > The carrier_on/off work will be scheduled when netvsc_open() is
> > called. Then, the status will be updated based on the latest link_state.
> >
> > Thanks,
> > - Haiyang
> >
> 
> I see. Then if the link status is changing during mtu changing in guest.
> Looks like we may miss a link status updating?

When changing mtu, rndis_filter_device_add() is called, and host will send a link
status call back immediately after connect-to-netvsp, no matter the link is changing
or not. This will schedule a work to update the status.

Thanks,
- Haiyang

RE: [PATCH net-next] hyperv: Move state setting for link query

[Haiyang Zhang]

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@redhat.com]
> Sent: Monday, March 3, 2014 10:10 PM
> To: Haiyang Zhang; davem@davemloft.net; netdev@vger.kernel.org
> Cc: KY Srinivasan; olaf@aepfle.de; linux-kernel@vger.kernel.org; driverdev-
> devel@linuxdriverproject.org
> Subject: Re: [PATCH net-next] hyperv: Move state setting for link query
> 
> On 03/04/2014 07:54 AM, Haiyang Zhang wrote:
> > It moves the state setting for query into rndis_filter_receive_response().
> > All callbacks including query-complete and status-callback are
> > synchronized by channel->inbound_lock. This prevents pentential race
> between them.
> 
> This still looks racy to me. The problem is workqueue is not synchronized with
> those here.
> 
> Consider the following case in netvsc_link_change():
> 
>     if (rdev->link_state) {
>     ... receive interrupt ...
>     rndis_filter_receice_response() which changes rdev->link_state
>     ...
>         netif_carrier_off()
>     }
> 
> And also it need to schedule a work otherwise the link status is out of sync.

I will update this patch to schedule a work by the end of probe function.

Thanks,
- Haiyang