Messages in this thread | | | Date | Sun, 19 Sep 2010 18:39:50 +0400 | From | Vasiliy Kulikov <> | Subject | Re: [PATCH 10/14] scsi: osd: fix device_register() error handling |
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On Sun, Sep 19, 2010 at 16:26 +0200, Dan Carpenter wrote: > On Sun, Sep 19, 2010 at 04:55:07PM +0400, Vasiliy Kulikov wrote: > > If device_register() fails then call put_device(). > > See comment to device_register. > > > > Signed-off-by: Vasiliy Kulikov <segooon@gmail.com> > > --- ... > > Hm... So if device_register() fails then we should always call > device_put()? It seems like a lot of existing code does that but I > hadn't realized until now that that is how it works.
Yes, almost ALL code using device_register() is buggy :-(
> Why can't the device_put() just be added inside the device_register() so > the unwinding works automatically?
Because some code already calls device_put(). Also it is documented like not putting the device. However, I'm in doubt why it is written this way.
> Also if someone add some more stuff to the end of this function, will > the device_unregister() followed by a device_put() cause problems if we > unwind like this?
Yes, device_register() gets one reference, you should put in in both cases - when device_register() failed and when it succeeded, but only one time. device_unregister() puts it, so it is "double putting".
> +err_free_something: > + kfree(foo); > + device_unregister(&oud->class_dev); > > +err_put_device: > > + put_device(&oud->class_dev); > > err_put_cdev: > > cdev_del(&oud->cdev); > > err_put_disk: > > If that's the case then the put_device() should be called infront of the > goto.
As it is the last call that may fail, it is redundant. Or you mean for future, if someone adds more code after device_register()?
Thanks, -- Vasiliy
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