linux-kernel - Re: [PATCH 1/3] staging: comedi: amplc_dio200_common: prevent extra free

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Message-ID: <53D61775.2070106@mev.co.uk>
Date:	Mon, 28 Jul 2014 10:27:17 +0100
From:	Ian Abbott <abbotti@....co.uk>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Hartley Sweeten <HartleyS@...ionengravers.com>
CC:	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] staging: comedi: amplc_dio200_common: prevent extra
 free_irq()

On 2014-07-27 19:45, Greg Kroah-Hartman wrote:
> On Fri, Jul 25, 2014 at 06:23:10PM +0000, Hartley Sweeten wrote:
>> On Friday, July 25, 2014 10:07 AM, Ian Abbott wrote:
>>> `dio200_detach()` in "amplc_dio200.c" calls
>>> `amplc_dio200_common_detach()` in "amplc_dio200_common.c", followed by
>>> `comedi_legacy_detach()` in "../drivers.c".  Both of those functions
>>> call `free_irq()` if `dev->irq` is non-zero.  The second call produces a
>>> warning message because the handler has already been freed.  Prevent
>>> that by setting `dev->irq = 0` in `amplc_dio200_common_detach()`.
>>>
>>> Signed-off-by: Ian Abbott <abbotti@....co.uk>
>>> ---
>>>   drivers/staging/comedi/drivers/amplc_dio200_common.c | 4 +++-
>>>   1 file changed, 3 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/staging/comedi/drivers/amplc_dio200_common.c b/drivers/staging/comedi/drivers/amplc_dio200_common.c
>>> index 78700e8..3592e58 100644
>>> --- a/drivers/staging/comedi/drivers/amplc_dio200_common.c
>>> +++ b/drivers/staging/comedi/drivers/amplc_dio200_common.c
>>> @@ -1202,8 +1202,10 @@ void amplc_dio200_common_detach(struct comedi_device *dev)
>>>
>>>   	if (!thisboard || !devpriv)
>>>   		return;
>>> -	if (dev->irq)
>>> +	if (dev->irq) {
>>>   		free_irq(dev->irq, dev);
>>> +		dev->irq = 0;
>>> +	}
>>>   }
>>>   EXPORT_SYMBOL_GPL(amplc_dio200_common_detach);
>>
>> Ian,
>>
>> I have already gave a Reviewed-by signoff for this series.
>>
>> After looking over the code I think a cleaner solution would be to:
>>
>> 1) Use comedi_legacy_detach() directly for the (*detach) in the
>>     legacy ISA driver.
>> 2) Move the code from amplc_dio200_common_detach() into the
>>     (*detach) function for the PCI driver.
>> 3) Remove the exported function amplc_dio200_common_detach().
>
> So should I not apply these patches?
>
> confused,
>
> greg k-h

It fixes a bug (harmless, apart from a kernel warning), and does no 
harm, so might as well apply them.  Hartley's suggestion can be done later.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@....co.uk>        )=-
-=( Tel: +44 (0)161 477 1898   FAX: +44 (0)161 718 3587         )=-
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