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

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Message-ID: <20070331180806.55d572c8@gondolin.boeblingen.de.ibm.com>
Date:	Sat, 31 Mar 2007 18:08:06 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Tejun Heo <htejun@...il.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

On Sat, 31 Mar 2007 12:12:48 +0900,
Tejun Heo <htejun@...il.com> wrote:

> > Hm, but as long as dk0 is registered, it can be looked up and someone
> > could get a reference on it.
> 
> Yeah, exactly.  That's why any getting any kobject reference backed by a
> module must be accompanied by try_module_get().
> 
> int mydrv_get_dk(struct dk *dk)
> {
> 	rc = try_module_get(mydrv);
> 	if (rc)
> 		return rc;
> 	kobject_get(&dk->kobj);
> 	return 0;
> }

This works if the caller always knows which module to grab (I was
thinking about some tree-walking code).

> Exactly, in that case, module reference count must not be zero.  You and
> I are saying the same thing.  Why are we running in circle?

I hope we're not, it just makes one dizzy :)

I'll think some more about it...
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