Hi, Andrew
On 2017/6/22 11:35, Andrew Lunn wrote:
>> I don't think returning to user space is an option, because it mean
>> ethtool phy self test would fail because if availability of some software
>> resoure, which is not some application would expect. here is what I can
>> think of:
>>
>> driver/net/ethernet/hisilicon/hns/hns_ethtool.c
>> int phy_loopback_selftest(struct phy_device *dev)
>> {
>> int err;
>>
>> mutex_lock(dev->mutex);
>>
>> if (dev->drv->loopback)
>> err = dev->drv->loopback(dev, 1);
>>
>> if (err)
>> goto out;
>>
>> /* mac driver do the test*/
>> .................
>>
>>
>> if (dev->drv->loopback)
>> err = dev->drv->loopback(dev, 0);
>>
>> if (err)
>> goto out;
>>
>> out:
>> mutex_unlock(dev->mutex);
>> return err;
>> }
>
> I don't think you need a mutex here. dev_ioctl.c:
>
> case SIOCETHTOOL:
> dev_load(net, ifr.ifr_name);
> rtnl_lock();
> ret = dev_ethtool(net, &ifr);
> rtnl_unlock();
>
> So all ethtool operations are protected by the rtnl. You cannot have
> two tests running at once.
>
>> One question I can think of is that, how do we ensure mac driver enable and
>> disable phy loopback in pair, enable loopback after dev->mutex is taken,
>> disable loopback before dev->mutex is released?
>> I hope I am not missing something obvious, any suggestion and idea?
>
> You cannot ensure this. But it would be a pretty obvious bug.
>
Thanks for your reply, I will send a new patch based on the discussion above.
Please let me know if there is anything else need changing.
Best Regards
Yunsheng Lin
