Re: [PATCH] EDAC: core EDAC support code

Greg KH
2006-03-08T01:33:20Z

On Tue, Mar 07, 2006 at 08:03:41PM -0500, Dmitry Torokhov wrote:
> On Tuesday 07 March 2006 12:04, Greg KH wrote:
> > On Tue, Mar 07, 2006 at 08:47:44AM -0800, Dave Peterson wrote:
> > > Ok, how does this sound:
> > >
> > > - Modify EDAC so it uses kmalloc() to create the kobject.
> > > - Eliminate edac_memctrl_master_release(). Instead, use kfree() as
> > > the release method for the kobject. Here, it's important to use a
> > > function -outside- of EDAC as the release method since the core
> > > EDAC module may have been unloaded by the time the release method
> > > is called.
> >
> > No, if this happens then you are using the kobject incorrectly. How
> > could it be held if your module is unloaded? Don't you have the module
> > reference counting logic correct?
> >
>
> It is pretty hard to implement kobject handling correctly. Consider the
> following:
>
> rmmod device_driver < /sys/devices/pci0000:00/...../power/state
>
> for a driver that creates/destroys device objects.

I agree, that's one reason I really hate the "default" attributes :(

To do this "right" we need to make the attributes dynamically created
and the owner set to the proper module. I did that for the module core
code and it's on my todo list for the driver core too.

> Opening 'state' attribute will pin device structure into memory but will
> not increase _your_ module's refcount. It is nice if you have a subsystem
> core split from drivers code - then you can keep core module reference
> until device objects are gone and allow individual drivers be unloaded
> freely. But for single-module system it is pretty hard, that's why
> platform devices are popular.

They are popular for when you don't have a "bus", and rightfully so.

thanks,

greg k-h