linux-kernel - Re: Behaviour of device

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Message-ID: <8031.85.118.17.158.1204806681.squirrel@newgolddream.dyndns.info>
Date:	Thu, 6 Mar 2008 12:31:21 -0000 (UTC)
From:	"Adrian McMenamin" <adrian@...golddream.dyndns.info>
To:	"Greg KH" <greg@...ah.com>
Cc:	"Adrian McMenamin" <lkmladrian@...il.com>,
	"LKML" <linux-kernel@...r.kernel.org>,
	"linux-sh" <linux-sh@...r.kernel.org>
Subject: Re: Behaviour of device_register

On Wed, March 5, 2008 11:46 pm, Greg KH wrote:
> On Wed, Mar 05, 2008 at 11:25:48PM +0000, Adrian McMenamin wrote:
>> The observed behaviour for me is that it appears to be blocking the
>> vblank interrupt on my box (or more accurately stopping the workqueue
>> that the interrupt handler calls from running). And without the vblank
>> my bus won't process dma and so therefore the attempt to register the
>> device in question fails.
>>
>> But I can see no reason from a glance over the code why that (vblanks
>> being blocked) would be the case - have I missed something and the
>> vblanks will be blocked, or should I be looking elsewhere for the root
>> cause of this problem?
>
> device_register(), on it's own, does not touch any hardware, nor prevent
> anything else in the kernel from happening.
>
> So I think you need to look elsewhere, like into the bus that is doing
> the device_register() call :)
>


It turns out this is a lock contention issue.

The code blocks waiting for a lock that will never be freed.

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