[PATCH net] net: hyperv: initialize link status correctly

[PATCH net] net: hyperv: initialize link status correctly

[Jason Wang]

Call netif_carrier_on() after register_device(). Otherwise it won't work since
the device was still in NETREG_UNINITIALIZED state.

Fixes a68f9614614749727286f675d15f1e09d13cb54a
(hyperv: Fix race between probe and open calls)

Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Reported-by: Di Nie <dnie@redhat.com>
Tested-by: Di Nie <dnie@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/hyperv/netvsc_drv.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/hyperv/netvsc_drv.c b/drivers/net/hyperv/netvsc_drv.c
index 71baeb3..dc11601 100644
--- a/drivers/net/hyperv/netvsc_drv.c
+++ b/drivers/net/hyperv/netvsc_drv.c
@@ -444,13 +444,13 @@ static int netvsc_probe(struct hv_device *dev,
 	}
 	memcpy(net->dev_addr, device_info.mac_adr, ETH_ALEN);
 
-	netif_carrier_on(net);
-
 	ret = register_netdev(net);
 	if (ret != 0) {
 		pr_err("Unable to register netdev.\n");
 		rndis_filter_device_remove(dev);
 		free_netdev(net);
+	} else {
+		netif_carrier_on(net);
 	}
 
 	return ret;
-- 
1.8.3.2

Re: [PATCH net] net: hyperv: initialize link status correctly

[David Miller]

From: Jason Wang <jasowang@redhat.com>
Date: Mon, 27 Jan 2014 15:30:54 +0800

> Call netif_carrier_on() after register_device(). Otherwise it won't work since
> the device was still in NETREG_UNINITIALIZED state.
> 
> Fixes a68f9614614749727286f675d15f1e09d13cb54a
> (hyperv: Fix race between probe and open calls)
> 
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Reported-by: Di Nie <dnie@redhat.com>
> Tested-by: Di Nie <dnie@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>

A device up can occur at the moment you call register_netdevice(),
therefore that up call can see the carrier as down and fail or
similar.  So you really cannot resolve the carrier to be on in this
way.

Re: [PATCH net] net: hyperv: initialize link status correctly

[Jason Wang]

On 01/27/2014 04:35 PM, David Miller wrote:
> From: Jason Wang <jasowang@redhat.com>
> Date: Mon, 27 Jan 2014 15:30:54 +0800
>
>> Call netif_carrier_on() after register_device(). Otherwise it won't work since
>> the device was still in NETREG_UNINITIALIZED state.
>>
>> Fixes a68f9614614749727286f675d15f1e09d13cb54a
>> (hyperv: Fix race between probe and open calls)
>>
>> Cc: Haiyang Zhang <haiyangz@microsoft.com>
>> Cc: K. Y. Srinivasan <kys@microsoft.com>
>> Reported-by: Di Nie <dnie@redhat.com>
>> Tested-by: Di Nie <dnie@redhat.com>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
> A device up can occur at the moment you call register_netdevice(),
> therefore that up call can see the carrier as down and fail or
> similar.  So you really cannot resolve the carrier to be on in this
> way.

True, we need a workqueue to synchronize them.

Re: [PATCH net] net: hyperv: initialize link status correctly

[Ben Hutchings]

[-- Attachment #1.1: Type: text/plain, Size: 1274 bytes --]

On Mon, 2014-01-27 at 17:40 +0800, Jason Wang wrote:
> On 01/27/2014 04:35 PM, David Miller wrote:
> > From: Jason Wang <jasowang@redhat.com>
> > Date: Mon, 27 Jan 2014 15:30:54 +0800
> >
> >> Call netif_carrier_on() after register_device(). Otherwise it won't work since
> >> the device was still in NETREG_UNINITIALIZED state.
> >>
> >> Fixes a68f9614614749727286f675d15f1e09d13cb54a
> >> (hyperv: Fix race between probe and open calls)
> >>
> >> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> >> Cc: K. Y. Srinivasan <kys@microsoft.com>
> >> Reported-by: Di Nie <dnie@redhat.com>
> >> Tested-by: Di Nie <dnie@redhat.com>
> >> Signed-off-by: Jason Wang <jasowang@redhat.com>
> > A device up can occur at the moment you call register_netdevice(),
> > therefore that up call can see the carrier as down and fail or
> > similar.  So you really cannot resolve the carrier to be on in this
> > way.
> 
> True, we need a workqueue to synchronize them.

Whatever for?  All you need to do is:

	rtnl_lock();
	register_netdevice();
	netif_carrier_on();
	rtnl_unlock();

It would be nice if we could make the current code work with a change in
the core, though.

Ben.

-- 
Ben Hutchings
If at first you don't succeed, you're doing about average.

[-- Attachment #1.2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 828 bytes --]

[-- Attachment #2: Type: text/plain, Size: 169 bytes --]

_______________________________________________
devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

Re: [PATCH net] net: hyperv: initialize link status correctly

[Jason Wang]

On 01/27/2014 06:22 PM, Ben Hutchings wrote:
> On Mon, 2014-01-27 at 17:40 +0800, Jason Wang wrote:
>> On 01/27/2014 04:35 PM, David Miller wrote:
>>> From: Jason Wang <jasowang@redhat.com>
>>> Date: Mon, 27 Jan 2014 15:30:54 +0800
>>>
>>>> Call netif_carrier_on() after register_device(). Otherwise it won't work since
>>>> the device was still in NETREG_UNINITIALIZED state.
>>>>
>>>> Fixes a68f9614614749727286f675d15f1e09d13cb54a
>>>> (hyperv: Fix race between probe and open calls)
>>>>
>>>> Cc: Haiyang Zhang <haiyangz@microsoft.com>
>>>> Cc: K. Y. Srinivasan <kys@microsoft.com>
>>>> Reported-by: Di Nie <dnie@redhat.com>
>>>> Tested-by: Di Nie <dnie@redhat.com>
>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>> A device up can occur at the moment you call register_netdevice(),
>>> therefore that up call can see the carrier as down and fail or
>>> similar.  So you really cannot resolve the carrier to be on in this
>>> way.
>> True, we need a workqueue to synchronize them.
> Whatever for?  All you need to do is:
>
> 	rtnl_lock();
> 	register_netdevice();
> 	netif_carrier_on();
> 	rtnl_unlock();
>
> It would be nice if we could make the current code work with a change in
> the core, though.
>
> Ben.
>

Looks like the link status interrupt may happen during this (after
netvsc_device_add() was called by rndis_filter_device_add()) without any
synchronization. This may lead a wrong link status here.

Re: [PATCH net] net: hyperv: initialize link status correctly

[Ben Hutchings]

[-- Attachment #1.1: Type: text/plain, Size: 1785 bytes --]

On Mon, 2014-01-27 at 18:28 +0800, Jason Wang wrote:
> On 01/27/2014 06:22 PM, Ben Hutchings wrote:
> > On Mon, 2014-01-27 at 17:40 +0800, Jason Wang wrote:
> >> On 01/27/2014 04:35 PM, David Miller wrote:
> >>> From: Jason Wang <jasowang@redhat.com>
> >>> Date: Mon, 27 Jan 2014 15:30:54 +0800
> >>>
> >>>> Call netif_carrier_on() after register_device(). Otherwise it won't work since
> >>>> the device was still in NETREG_UNINITIALIZED state.
> >>>>
> >>>> Fixes a68f9614614749727286f675d15f1e09d13cb54a
> >>>> (hyperv: Fix race between probe and open calls)
> >>>>
> >>>> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> >>>> Cc: K. Y. Srinivasan <kys@microsoft.com>
> >>>> Reported-by: Di Nie <dnie@redhat.com>
> >>>> Tested-by: Di Nie <dnie@redhat.com>
> >>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
> >>> A device up can occur at the moment you call register_netdevice(),
> >>> therefore that up call can see the carrier as down and fail or
> >>> similar.  So you really cannot resolve the carrier to be on in this
> >>> way.
> >> True, we need a workqueue to synchronize them.
> > Whatever for?  All you need to do is:
> >
> > 	rtnl_lock();
> > 	register_netdevice();
> > 	netif_carrier_on();
> > 	rtnl_unlock();
> >
> > It would be nice if we could make the current code work with a change in
> > the core, though.
> >
> > Ben.
> >
> 
> Looks like the link status interrupt may happen during this (after
> netvsc_device_add() was called by rndis_filter_device_add()) without any
> synchronization. This may lead a wrong link status here.

Now I'm confused - if there's a link status interrupt, why are you
setting the carrier on initially?

Ben.

-- 
Ben Hutchings
If at first you don't succeed, you're doing about average.

[-- Attachment #1.2: This is a digitally signed message part --]
[-- Type: application/pgp-signature, Size: 828 bytes --]

[-- Attachment #2: Type: text/plain, Size: 169 bytes --]

_______________________________________________
devel mailing list
devel@linuxdriverproject.org
http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel

Re: [PATCH net] net: hyperv: initialize link status correctly

[Jason Wang]

On 01/27/2014 06:30 PM, Ben Hutchings wrote:
> On Mon, 2014-01-27 at 18:28 +0800, Jason Wang wrote:
>> On 01/27/2014 06:22 PM, Ben Hutchings wrote:
>>> On Mon, 2014-01-27 at 17:40 +0800, Jason Wang wrote:
>>>> On 01/27/2014 04:35 PM, David Miller wrote:
>>>>> From: Jason Wang <jasowang@redhat.com>
>>>>> Date: Mon, 27 Jan 2014 15:30:54 +0800
>>>>>
>>>>>> Call netif_carrier_on() after register_device(). Otherwise it won't work since
>>>>>> the device was still in NETREG_UNINITIALIZED state.
>>>>>>
>>>>>> Fixes a68f9614614749727286f675d15f1e09d13cb54a
>>>>>> (hyperv: Fix race between probe and open calls)
>>>>>>
>>>>>> Cc: Haiyang Zhang <haiyangz@microsoft.com>
>>>>>> Cc: K. Y. Srinivasan <kys@microsoft.com>
>>>>>> Reported-by: Di Nie <dnie@redhat.com>
>>>>>> Tested-by: Di Nie <dnie@redhat.com>
>>>>>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>>>>> A device up can occur at the moment you call register_netdevice(),
>>>>> therefore that up call can see the carrier as down and fail or
>>>>> similar.  So you really cannot resolve the carrier to be on in this
>>>>> way.
>>>> True, we need a workqueue to synchronize them.
>>> Whatever for?  All you need to do is:
>>>
>>> 	rtnl_lock();
>>> 	register_netdevice();
>>> 	netif_carrier_on();
>>> 	rtnl_unlock();
>>>
>>> It would be nice if we could make the current code work with a change in
>>> the core, though.
>>>
>>> Ben.
>>>
>> Looks like the link status interrupt may happen during this (after
>> netvsc_device_add() was called by rndis_filter_device_add()) without any
>> synchronization. This may lead a wrong link status here.
> Now I'm confused - if there's a link status interrupt, why are you
> setting the carrier on initially?
>
> Ben.
>

I realize that setting carrier on initially was a bug after David's
comment. So I think we need a workqueue.

RE: [PATCH net] net: hyperv: initialize link status correctly

[Haiyang Zhang]

> -----Original Message-----
> From: Jason Wang [mailto:jasowang@redhat.com]
> Sent: Monday, January 27, 2014 2:31 AM
> To: KY Srinivasan; Haiyang Zhang; devel@linuxdriverproject.org;
> netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Cc: Jason Wang
> Subject: [PATCH net] net: hyperv: initialize link status correctly
> 
> Call netif_carrier_on() after register_device(). Otherwise it won't work since
> the device was still in NETREG_UNINITIALIZED state.
> 
> Fixes a68f9614614749727286f675d15f1e09d13cb54a
> (hyperv: Fix race between probe and open calls)
> 
> Cc: Haiyang Zhang <haiyangz@microsoft.com>
> Cc: K. Y. Srinivasan <kys@microsoft.com>
> Reported-by: Di Nie <dnie@redhat.com>
> Tested-by: Di Nie <dnie@redhat.com>
> Signed-off-by: Jason Wang <jasowang@redhat.com>
> ---

I'm working on a fix for this, and will submit it soon.

Thanks,
- Haiyang