Messages in this thread | | | Subject | Re: [RFC PATCH v5 2/2] Use kernfs_break_active_protection() for device online store callbacks | From | Li Zhong <> | Date | Tue, 22 Apr 2014 11:34:39 +0800 |
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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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