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

[Brian Norris]

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? Shouldn't both drivers just be
registered/unregistered in the module init/exit, and not in probe()?

Also, should this be marked for -stable?

> Signed-off-by: Josh Wu <josh.wu at atmel.com>
> ---
>  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