Re: [PATCH 2.6.10-rc1 2/5] driver-model: bus_recan_devices() locking fix

[Greg KH <greg@kroah.com>]

On Tue, Nov 09, 2004 at 11:17:31PM -0500, Dmitry Torokhov wrote:
> On Tuesday 09 November 2004 07:40 pm, Greg KH wrote:
> > > I think we just have lay down the rules that one needs to get a reference
> > > to an object in the following cases:
> > > - object creation (first reference)
> > > - linking some other object to the object in question. Every link to the
> > > ? object should increase reference count.
> > > - before passing object to another thread of execution to guarantee that
> > > ? the object will live long enough for both threads.
> > 
> > The rules are defined. ?See my OLS 2004 paper on krefs for details.
> > 
> 
> So that means you will patches like the one below, right?
> 
> diff -Nru a/drivers/base/driver.c b/drivers/base/driver.c
> --- a/drivers/base/driver.c	2004-11-09 23:16:43 -05:00
> +++ b/drivers/base/driver.c	2004-11-09 23:16:43 -05:00
> @@ -26,13 +26,7 @@
>  
>  int driver_create_file(struct device_driver * drv, struct driver_attribute * attr)
>  {
> -	int error;
> -	if (get_driver(drv)) {
> -		error = sysfs_create_file(&drv->kobj, &attr->attr);
> -		put_driver(drv);
> -	} else
> -		error = -EINVAL;
> -	return error;
> +	return sysfs_create_file(&drv->kobj, &attr->attr);
>  }
>  
>  
> @@ -44,10 +38,7 @@
>  
>  void driver_remove_file(struct device_driver * drv, struct driver_attribute * attr)
>  {
> -	if (get_driver(drv)) {
> -		sysfs_remove_file(&drv->kobj, &attr->attr);
> -		put_driver(drv);
> -	}
> +	sysfs_remove_file(&drv->kobj, &attr->attr);
>  }

While not totally necessary, the current code is safe :)

I'll ask Pat about this next time I see him.

thanks,

greg k-h