linux-kernel - Re: [bug, 2.6.26-rc4/rc5] sporadic bootup crashes in blk_lookup_devt()/prepare

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Message-ID: <20080610215218.GC16256@suse.de>
Date:	Tue, 10 Jun 2008 14:52:18 -0700
From:	Greg KH <gregkh@...e.de>
To:	Cornelia Huck <cornelia.huck@...ibm.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Vegard Nossum <vegard.nossum@...il.com>,
	Adrian Bunk <bunk@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kay Sievers <kay.sievers@...y.org>, Neil Brown <neilb@...e.de>,
	Mariusz Kozlowski <m.kozlowski@...land.pl>,
	Dave Young <hidave.darkstar@...il.com>
Subject: Re: [bug, 2.6.26-rc4/rc5] sporadic bootup crashes in
	blk_lookup_devt()/prepare_namespace()

On Tue, Jun 10, 2008 at 09:51:22AM +0200, Cornelia Huck wrote:
> On Mon, 9 Jun 2008 20:11:09 -0700,
> Greg KH <gregkh@...e.de> wrote:
> 
> > On Mon, Jun 09, 2008 at 07:15:21PM +0200, Cornelia Huck wrote:
> > > The driver core changes in -next convert class->sem to
> > > class->p->class_mutex, which makes it non-accessible to drivers.
> > > Most of the locking is easily done through converting to the class
> > > iterator functions, but there are some cases where this is not going to
> > > work:
> > > 
> > > - The {register,unregister}_blkdev() functions, which don't directly
> > > involve the class.
> > > - The iterators for /proc/partitions, which take the lock in
> > > part_start() and give it up again in part_stop().
> > > 
> > > Maybe we need a possibilty for a driver to lock a class from outside?
> > 
> > Why would that be needed?  We protect walking the class lists internally
> > with the lock, that should be sufficient, right?
> 
> What about the two functions I cited above? Don't we want them
> protected by the same lock?

For register/unregister, yes, we still need to protect the list of
major/minor numbers.

But for the proc/partitions list, I don't think we still need it
anymore, but I might be missing something here.  :)

thanks,

greg k-h
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