Hello, On Mon, Apr 14, 2014 at 03:47:29PM +0800, Li Zhong wrote: > @@ -439,6 +439,7 @@ static ssize_t online_store(struct device *dev, struct > device_attribute *attr, > { > bool val; > int ret; > + struct kernfs_node *kn; > > ret = strtobool(buf, &val); > if (ret < 0) > @@ -448,7 +449,19 @@ static ssize_t online_store(struct device *dev, struct > device_attribute *attr, > if (ret) > return ret; > > + kn = kernfs_find_and_get(dev->kobj.sd, attr->attr.name); > + if (WARN_ON_ONCE(!kn)) > + goto out; > + > + get_device(dev); > + kernfs_break_active_protection(kn); > ret = val ? device_online(dev) : device_offline(dev); > + kernfs_unbreak_active_protection(kn); > + put_device(dev); > + > + kernfs_put(kn); > + > +out: > unlock_device_hotplug(); > return ret < 0 ? ret : count; > }
Can you please add comment explainin why this is being down? As it currently stands, it's quite a bit of complexity without any indication what's going on why. Also, if device_hotplug is locked, is it really necessary to get @dev? Can it go away inbetween? The code snippet looks weird because getting @dev indicates that the device might go away without doing it but then it proceeds to invoke device_{on|off}line() which probably isn't safe to invoke on a removed device. Thanks. -- tejun -- 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/