On Mon, 2014-04-21 at 18:46 -0400, Tejun Heo wrote:
> Hello,
>
> On Mon, Apr 21, 2014 at 05:23:50PM +0800, Li Zhong wrote:
>
> Proper /** function comment would be nice.
Ok, will try to write some in next version.
>
> > +struct kernfs_node *lock_device_hotplug_sysfs(struct device *dev,
> > + struct device_attribute *attr)
>
> I can see why you did this but let's please not require the user of
> this function to see how the thing is working internally. Let's
> return int and keep track of (or look up again) the kernfs_node
> internally.
Ok, it also makes the prototype of lock and unlock look more consistent
and comfortable.
>
> > {
> ...
> > + /*
> > + * We assume device_hotplug_lock must be acquired before removing
>
> Is this assumption true? If so, can we add lockdep assertions in
> places to verify and enforce this? If not, aren't we just feeling
> good when the reality is broken?
It seems not true ... I think there are devices that don't have the
online/offline concept, we just need to add it, remove it, like ethernet
cards.
Maybe we could change the comments above, like:
/* We assume device_hotplug_lock must be acquired before
* removing devices, which have online/offline sysfs knob,
* and some locks are needed to serialize the online/offline
* callbacks and device removing. ...
?
And we could add lockdep assertions in cpu and memory related code? e.g.
remove_memory(), unregister_cpu()
Currently, remove_memory() has comments for the function:
* NOTE: The caller must call lock_device_hotplug() to serialize hotplug
* and online/offline operations before this call, as required by
* try_offline_node().
*/
maybe it could be removed with the lockdep assertion.
> ...
>
> Function comment please.
OK.
Thanks, Zhong
> > +void unlock_device_hotplug_sysfs(struct device *dev,
> > + struct kernfs_node *kn)
> > +{
> > + unlock_device_hotplug();
> > + kernfs_unbreak_active_protection(kn);
> > + put_device(dev);
> > + kernfs_put(kn);
> > }
>
> Thanks.
>
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