linux-kernel - Re: [RFD driver-core] Lifetime problems of the current driver model

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Message-ID: <460D0E78.3040200@gmail.com>
Date:	Fri, 30 Mar 2007 22:19:52 +0900
From:	Tejun Heo <htejun@...il.com>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
CC:	gregkh@...e.de, hugh@...itas.com, dmitry.torokhov@...il.com,
	oneukum@...e.de, maneesh@...ibm.com, rpurdie@...ys.net,
	James.Bottomley@...elEye.com, Jeff Garzik <jgarzik@...ox.com>,
	lkml <linux-kernel@...r.kernel.org>,
	"linux-ide@...r.kernel.org" <linux-ide@...r.kernel.org>,
	SCSI Mailing List <linux-scsi@...r.kernel.org>
Subject: Re: [RFD driver-core] Lifetime problems of the current driver model

Cornelia Huck wrote:
> On Fri, 30 Mar 2007 18:43:02 +0900,
> Tejun Heo <htejun@...il.com> wrote:
> 
>> One way to solve this problem is to subordinate lifetime rule #b to
>> rule #c.  Each kobject points to its owning module such that grabbing
>> a kobject automatically grabs the module.  The problem with this
>> approach is that it requires wide update and makes kobject_get
>> heavier.
> 
> Shouldn't getting/putting the module refcount be solely done in
> kobject.c? Grab the module reference when the kobject is created and
> release the module reference in kobject_cleanup() after the release
> function has been called. This doesn't make kobject_get() heavier, and
> it ensures we don't delete the module until after the last kobject it is
> supposed to clean up has been released.

If we do that, we wouldn't be able to unload a module if there is any
kobject referencing it even when the node has no openers, so no easy way
out there.  :-(

-- 
tejun
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