netdev - Re: [patch net-next v2 4/7] switchdev: introduce possibility to defer obj

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Message-ID: <20151012145718.GG2370@nanopsycho.orion>
Date:	Mon, 12 Oct 2015 16:57:18 +0200
From:	Jiri Pirko <jiri@...nulli.us>
To:	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Cc:	netdev@...r.kernel.org, davem@...emloft.net, idosch@...lanox.com,
	eladr@...lanox.com, sfeldma@...il.com, f.fainelli@...il.com,
	linux@...ck-us.net, vivien.didelot@...oirfairelinux.com,
	andrew@...n.ch, john.fastabend@...il.com, David.Laight@...LAB.COM,
	stephen@...workplumber.org
Subject: Re: [patch net-next v2 4/7] switchdev: introduce possibility to
 defer obj_add/del

Mon, Oct 12, 2015 at 04:42:12PM CEST, nikolay@...ulusnetworks.com wrote:
>On 10/12/2015 04:34 PM, Nikolay Aleksandrov wrote:
>> On 10/12/2015 03:15 PM, Jiri Pirko wrote:
>>> From: Jiri Pirko <jiri@...lanox.com>
>>>
>>> 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 <jiri@...lanox.com>
>>> ---
>>>  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/ ? :-)
>> 
>>> +};
>>> +
>>> +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 ?
>> 
>Nevermind this question, got it.

Well anyone without rtnl should hold dev in the first place. So this
should be ok.
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