Subject: Re: [patch net-next v2 4/7] switchdev: introduce possibility to defer obj_add/del

From: Nikolay Aleksandrov <[email-masked]>
Date: Mon, 12 Oct 2015 16:46:53 +0200

On 10/12/2015 04:44 PM, Jiri Pirko wrote:
> Mon, Oct 12, 2015 at 04:34:25PM CEST, [email-masked] wrote:
>> On 10/12/2015 03:15 PM, Jiri Pirko wrote:
>>> From: Jiri Pirko <[email-masked]>
>>>
>>> Similar to the attr usecase, the caller knows if he is holding RTNL and is
>>> in atomic section. So let the called to decide the correct call variant.
>>>
>>> This allows drivers to sleep inside their ops and wait for hw to get the
>>> operation status. Then the status is propagated into switchdev core.
>>> This avoids silent errors in drivers.
>>>
>>> Signed-off-by: Jiri Pirko <[email-masked]>
>>> ---
>>>  include/net/switchdev.h   |   1 +
>>>  net/switchdev/switchdev.c | 137 +++++++++++++++++++++++++++++++++++++---------
>>>  2 files changed, 112 insertions(+), 26 deletions(-)
>>>
>> [snip]
>>> +
>>> +struct switchdev_obj_work {
>>> +	struct work_struct work;
>>> +	struct net_device *dev;
>>> +	struct switchdev_obj obj;
>>> +	bool add; /* add of del */
>> s/of/or/ ? :-)
> 
> will fix, thanks.
> 
> 
>>
>>> +};
>>> +
>>> +static void switchdev_port_obj_work(struct work_struct *work)
>>> +{
>>> +	struct switchdev_obj_work *ow =
>>> +			container_of(work, struct switchdev_obj_work, work);
>>> +	bool rtnl_locked = rtnl_is_locked();
>>> +	int err;
>>> +
>>> +	if (!rtnl_locked)
>>> +		rtnl_lock();
>>> +	if (ow->add)
>>> +		err = switchdev_port_obj_add_now(ow->dev, &ow->obj);
>>> +	else
>>> +		err = switchdev_port_obj_del_now(ow->dev, &ow->obj);
>>> +	if (err && err != -EOPNOTSUPP)
>>> +		netdev_err(ow->dev, "failed (err=%d) to %s object (id=%d)\n",
>>> +			   err, ow->add ? "add" : "del", ow->obj.id);
>>> +	if (!rtnl_locked)
>>> +		rtnl_unlock();
>>> +
>>> +	dev_put(ow->dev);
>>> +	kfree(ow);
>>> +}
>>> +
>>> +static int switchdev_port_obj_work_schedule(struct net_device *dev,
>>> +					    const struct switchdev_obj *obj,
>>> +					    bool add)
>>> +{
>>> +	struct switchdev_obj_work *ow;
>>> +
>>> +	ow = kmalloc(sizeof(*ow), GFP_ATOMIC);
>>> +	if (!ow)
>>> +		return -ENOMEM;
>>> +
>>> +	INIT_WORK(&ow->work, switchdev_port_obj_work);
>>> +
>> This can be called without rtnl, what stops the device from disappearing
>> between the above and the hold below ?
> 
> You are right. I will have to figure that out. Btw the same issue
> already exists for attr_set deferred work.
> 
> 

I have to say there're a few users now that need delayed RTNL execution
the bonding being a heavy one, teaming I think also has some rtnl delays.
Maybe it's time we do a generic delayed rtnl execution so it can be re-used
by all.