Subject: [PATCH] mtd: atmel_nand: fix bug driver will in a dead lock if no nand detected

From: [email-masked] (Nicolas Ferre)
Date: Thu, 7 Nov 2013 11:55:07 +0100

On 07/11/2013 11:26, Josh Wu :
> Hi, Brian
>
> On 11/7/2013 4:39 PM, Brian Norris wrote:
>> Hi Josh,
>>
>> On Tue, Nov 05, 2013 at 05:59:07PM +0800, Josh Wu wrote:
>>> In the atmel driver probe function, the code shows like following:
>>>     atmel_nand_probe(...) {
>>>           ...
>>>
>>>     err_nand_ioremap:
>>>           platform_driver_unregister(&atmel_nand_nfc_driver);
>>>           return res;
>>>     }
>>>
>>> If no nand flash detected, the driver probe function will goto
>>> err_nand_ioremap label.
>>> Then platform_driver_unregister() will be called. It will get the
>>> lock of atmel_nand device since it is parent of nfc_device. The
>>> problem is the lock is already hold by atmel_nand_probe itself.
>>> So system will be in a dead lock.
>>>
>>> This patch just simply removed to platform_driver_unregister() call.
>>> When atmel_nand driver is quit the platform_driver_unregister() will
>>> be called in atmel_nand_remove().
>> The real key, here, is that the platform-driver probe() has no business
>> un-registering another driver, right?
>
> right.
>
>> Shouldn't both drivers just be
>> registered/unregistered in the module init/exit, and not in probe()?
>
> currently the NFC driver is registered in the beginning of nand probe
> function. After NFC driver is initialized, the rest of the nand probe
> function
> will check the NFC driver status.
> I am not sure it is proper to registered another driver in a probe().
>
>>
>> Also, should this be marked for -stable?
>
> Shouldn't cc to stable after the patch is merged in mtd mail list?

Whether you add a Cc: tag in your signature location or you send another 
patch to the stable mailing list *but* only when the patch is accepted 
in Linus' git tree.

You can find the information in
Documentation/stable_kernel_rules.txt

Bye,

>>> Signed-off-by: Josh Wu <[email-masked]>
>>> ---
>>>    drivers/mtd/nand/atmel_nand.c |    1 -
>>>    1 file changed, 1 deletion(-)
>>>
>>> diff --git a/drivers/mtd/nand/atmel_nand.c b/drivers/mtd/nand/atmel_nand.c
>>> index ef9c9f5..469d4e2 100644
>>> --- a/drivers/mtd/nand/atmel_nand.c
>>> +++ b/drivers/mtd/nand/atmel_nand.c
>>> @@ -2142,7 +2142,6 @@ err_no_card:
>>>    	if (host->dma_chan)
>>>    		dma_release_channel(host->dma_chan);
>>>    err_nand_ioremap:
>>> -	platform_driver_unregister(&atmel_nand_nfc_driver);
>>>    	return res;
>>>    }
>>>
>> Brian
>
>
>

-- 
Nicolas Ferre