linux-kernel - Re: pktcdvd oops

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Date:	Tue, 06 Nov 2007 22:07:32 +0100
From:	"Thomas Maier" <balagi@...tmail.de>
To:	"Tejun Heo" <htejun@...il.com>,
	"Peter Osterlund" <petero2@...ia.com>
Cc:	"Jens Axboe" <jens.axboe@...cle.com>,
	linux-kernel <linux-kernel@...r.kernel.org>, gregkh@...e.de
Subject: Re: pktcdvd oops

Hello,

have not tested it yet, but i quess, the code mentioned by Peter
is in pkt_new_dev() that is called by pkt_setup_dev():

	/* This is safe, since we have a reference from open(). */
		__module_get(THIS_MODULE);


So, now, there must be checks in every sysfs operation in the module code,
to ensure that the module is still loaded?

BTW: the bug report says:

  Steps to reproduce:

   modprobe pktcdvd
   echo 22:0 >/sys/class/pktcdvd/add

Is there any module unload??? Why is the module not available after the modprobe, but the sysfs entries, generated by the module? Confused ;)

-Thomas


Am 06.11.2007, 10:06 Uhr, schrieb Tejun Heo <htejun@...il.com>:

> [Greg cc'd]
>
> Peter Osterlund wrote:
>> On Mon, 5 Nov 2007, Jens Axboe wrote:
>>
>>> Hi Peter,
>>>
>>> You don't seem to have a bugzilla account, so could not reassign to you.
>>> See http://bugzilla.kernel.org/show_bug.cgi?id=9294
>>
>> Problem is repeatable on my computer. It dies in __module_get() on this
>> line:
>>
>>         BUG_ON(module_refcount(module) == 0);
>>
>> I think this is because commit 7b595756ec1f49e0049a9e01a1298d53a7faaa15,
>> which states: "Note that with this change, userland holding a sysfs node
>> does not prevent the backing module from being unloaded."
>>
>> Unfortunately, I don't know how this sysfs stuff is supposed to work,
>> and therefore don't know how to fix the problem.
>
> Does this fix the problem?
>


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