viOn Tue, 2014-04-22 at 11:34 +0800, Li Zhong wrote: > 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.
When trying to do an new version of the patch, I find that if the device is really removed, then we couldn't look up using the parent, and attribute name again in unlock. So I guess maybe I could add one more argument, e.g. kn_out,:q to track this kernfs node. Code will be posted soon for your review. Thanks, Zhong > > > > > > { > > ... > > > + /* > > > + * 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. > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/