linux-kernel - Re: [PATCH 1/2] dev-core: fix build break when DEBUG is enabled

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Date:	Thu, 15 Aug 2013 19:53:13 +0300
From:	Dmitry Kasatkin <d.kasatkin@...sung.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, sarah.a.sharp@...ux.intel.com,
	dmitry.kasatkin@...il.com, stable@...r.kernel.org
Subject: Re: [PATCH 1/2] dev-core: fix build break when DEBUG is enabled

On 15/08/13 19:37, Greg KH wrote:
> On Thu, Aug 15, 2013 at 07:04:54PM +0300, Dmitry Kasatkin wrote:
>> When DEBUG is defined, dev_dbg_ratelimited uses dynamic debug data
>> structures even when CONFIG_DYNAMIC_DEBUG is not defined.
>> It leads to build break.
>> For example, when I try to use dev_dbg_ratelimited in USB code and
>> CONFIG_USB_DEBUG is enabled, but CONFIG_DYNAMIC_DEBUG is not, I get:
>>
>>   CC [M]  drivers/usb/host/xhci-ring.o
>>   drivers/usb/host/xhci-ring.c: In function ‘xhci_queue_intr_tx’:
>>   drivers/usb/host/xhci-ring.c:3059:3: error: implicit declaration of function ‘DEFINE_DYNAMIC_DEBUG_METADATA’ [-Werror=implicit-function-declaration]
>>   drivers/usb/host/xhci-ring.c:3059:3: error: ‘descriptor’ undeclared (first use in this function)
>>   drivers/usb/host/xhci-ring.c:3059:3: note: each undeclared identifier is reported only once for each function it appears in
>>   drivers/usb/host/xhci-ring.c:3059:3: error: implicit declaration of function ‘__dynamic_pr_debug’ [-Werror=implicit-function-declaration]
>>   drivers/usb/host/xhci-ring.c: In function ‘xhci_queue_isoc_tx_prepare’:
>>   drivers/usb/host/xhci-ring.c:3847:3: error: ‘descriptor’ undeclared (first use in this function)
>>   cc1: some warnings being treated as errors
>>   make[2]: *** [drivers/usb/host/xhci-ring.o] Error 1
>>   make[1]: *** [drivers/usb/host] Error 2
>>   make: *** [drivers/usb/] Error 2
>>
>> This patch separates definition for CONFIG_DYNAMIC_DEBUG and DEBUG cases.
>>
>> Signed-off-by: Dmitry Kasatkin <d.kasatkin@...sung.com>
>> Cc: stable@...r.kernel.org
> How is this a stable issue?  I don't see how the rules listed in
> Documentation/stable_kernel_rules.txt apply here, what am I missing?
>
> Not to say your patch isn't correct, just that it's not stable material,
> right?
>
> thanks,
>
> greg k-h
>

There are few drivers which uses dev_dbg_ratelimited().
In the case someone tries to build kernel with those drivers with DEBUG
enabled and without CONFIG_DYNAMIC_DEBUG,
will get the build break. It will happen also on stable kernel.

- Dmitry

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