netdev - Re: [PATCH net-next] phylink: add ASSERT_RTNL() on phylink connect functions

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Date:   Wed, 23 Oct 2019 15:59:30 +0000
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "andrew@...n.ch" <andrew@...n.ch>
Subject: Re: [PATCH net-next] phylink: add ASSERT_RTNL() on phylink connect
 functions

On 10/23/19 4:10 PM, Russell King - ARM Linux admin wrote:
> On Wed, Oct 23, 2019 at 03:32:20PM +0300, Ioana Ciornei wrote:
>> The appropriate assert on the rtnl lock is not present in phylink's
>> connect functions which makes unusual calls to them not to be catched.
>> Add the appropriate ASSERT_RTNL().
> 
> As I previously replied, this is not necessary.  It is safe to attach
> PHYs _prior_ to the netdev being registered without taking the rtnl
> lock, just like phylib's phy_connect()/phy_attach() are safe.
>

Yeah.. I was trying to catch other errors like in the case of dpaa2-eth 
where we also connect/disconnect when we are notified by the firmware of 
a DPMAC disconnect.

I now understand why the assert is not always needed in the _connect().

Ioana

>>
>> Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
>> ---
>>   drivers/net/phy/phylink.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
>> index be7a2c0fa59b..d0aa0c861b2d 100644
>> --- a/drivers/net/phy/phylink.c
>> +++ b/drivers/net/phy/phylink.c
>> @@ -786,6 +786,8 @@ static int __phylink_connect_phy(struct phylink *pl, struct phy_device *phy,
>>    */
>>   int phylink_connect_phy(struct phylink *pl, struct phy_device *phy)
>>   {
>> +	ASSERT_RTNL();
>> +
>>   	/* Use PHY device/driver interface */
>>   	if (pl->link_interface == PHY_INTERFACE_MODE_NA) {
>>   		pl->link_interface = phy->interface;
>> @@ -815,6 +817,8 @@ int phylink_of_phy_connect(struct phylink *pl, struct device_node *dn,
>>   	struct phy_device *phy_dev;
>>   	int ret;
>>   
>> +	ASSERT_RTNL();
>> +
>>   	/* Fixed links and 802.3z are handled without needing a PHY */
>>   	if (pl->link_an_mode == MLO_AN_FIXED ||
>>   	    (pl->link_an_mode == MLO_AN_INBAND &&
>> -- 
>> 1.9.1
>>
>>
>