linux-kernel - Re: 2.6.28-rc2: (mtd)block/partitions BUG with kobject reference count

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Message-ID: <ac3eb2510810301451x7dbf18edgd03c1433099ce5e4@mail.gmail.com>
Date:	Thu, 30 Oct 2008 22:51:41 +0100
From:	"Kay Sievers" <kay.sievers@...y.org>
To:	"Peter Korsgaard" <jacmet@...site.dk>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, linux-mtd@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.28-rc2: (mtd)block/partitions BUG with kobject reference count

On Thu, Oct 30, 2008 at 00:28, Peter Korsgaard <jacmet@...site.dk> wrote:
>>>>>> "Rafael" == Rafael J Wysocki <rjw@...k.pl> writes:
>
>  Rafael> On Wednesday, 29 of October 2008, Peter Korsgaard wrote:
>  >> Hi,
>  >>
>  >> I'm seing what looks like a kobject reference count issue with
>  >> mtdblock_ro + mtd_dataflash + mtd partitions and repeated unbind/bind.
>  >> I'm on 2.6.28-rc2, but I can reproduce the problem on 2.6.27 as well.
>
>  Rafael> Is it reproducible with 2.6.26 too?
>
> Sorry, I haven't backported my platform support code to such "old"
> kernel. I can do it though, if you think it will help pinpoint the
> issue.

This sounds like a possible reason for the problem:
"After digging into the mtd code, this bug is not related to our driver. It
should be a subtle bug in mtd core code.

In add_mtd_partition, for 2 partitions, 2 gendisk structures will be
allocated. But these 2 gendisk->queue will be set to the same
request_queue. Then when unregistering the 1st partition, from the
same request_queue->backing_dev_info, the bdi struct will be set to
NULL. So for the 2nd partition (bdi == NULL), the sysfs dir of 2nd
partition will not be removed. Finally, when modprobe the module
again, the 2nd partition won't be added"
https://blackfin.uclinux.org/gf/tracker/4463

Kay
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