linux-kernel - Re: [PATCH 0/4] treewide: add missing put

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Message-ID: <52AF4249.8030000@linux.com>
Date:	Mon, 16 Dec 2013 19:11:21 +0100
From:	Levente Kurusa <levex@...ux.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:	Bjorn Helgaas <bhelgaas@...gle.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/4] treewide: add missing put_device calls

On 12/16/2013 06:58 PM, Greg Kroah-Hartman wrote:
> On Mon, Dec 16, 2013 at 06:18:53PM +0100, Levente Kurusa wrote:
>>>> IIRC, there are also a few where the device is also unregistered from
>>>> the specific subsystem's core.
>>>
>>> Do you have a specific example of this?  This should happen in the
>>> release function of the device already, not in some other code.
>>>
>> Character drivers who register with device_register() call cdev_del()
>> when device_register() fails.
> 
> A cdev shouldn't be created until _after_ the device is successfully
> registered, as it could be opened and accessed before the device is
> registered.  That sounds like the drivers that do that should be fixed
> (have an example of this somewhere?)

I did some research and it seems it has mostly been my false memory that made
me think that. The only example I could find that did something like this
was: drivers/scsi/osd/osd_uld.c at line 403.

When the device_register() fails it immediately jumps to a cdev_del();
> 
>> cdev_del() in turn calls kobject_put on the kobject of the device.
> 
> Which device?  Don't get confused about the internal kobject for a cdev,
> that's a totally different thing.
> 
Ah yes, now I see this. I thought that they shared a kobject, but now thinking
a bit better on this that wouldn't even make sense.


-- 
Regards,
Levente Kurusa
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