linux-kernel - Re: [PATCH] staging: gdm72xx: conditionally compile debug code

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Message-ID: <53BD9D67.8090806@fastmail.fm>
Date:	Wed, 09 Jul 2014 20:52:07 +0100
From:	Michalis Pappas <mpappas@...tmail.fm>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: gdm72xx: conditionally compile debug code

On 07/09/2014 07:51 PM, Greg KH wrote:
> On Tue, Jul 01, 2014 at 02:00:15PM +0100, Michalis Pappas wrote:
>> Signed-off-by: Michalis Pappas <mpappas@...tmail.fm>
>> ---
>>  drivers/staging/gdm72xx/gdm_qos.c   | 2 ++
>>  drivers/staging/gdm72xx/gdm_sdio.c  | 7 +++++++
>>  drivers/staging/gdm72xx/gdm_usb.c   | 7 +++++++
>>  drivers/staging/gdm72xx/gdm_wimax.c | 6 ++++++
>>  drivers/staging/gdm72xx/gdm_wimax.h | 2 ++
>>  5 files changed, 24 insertions(+)
>>
>> diff --git a/drivers/staging/gdm72xx/gdm_qos.c b/drivers/staging/gdm72xx/gdm_qos.c
>> index b08c8e1..7900981 100644
>> --- a/drivers/staging/gdm72xx/gdm_qos.c
>> +++ b/drivers/staging/gdm72xx/gdm_qos.c
>> @@ -88,7 +88,9 @@ static void free_qos_entry_list(struct list_head *free_list)
>>  		total_free++;
>>  	}
>>  
>> +	#if defined(GDM72xx_DEBUG)
>>  	pr_debug("%s: total_free_cnt=%d\n", __func__, total_free);
>> +	#endif
> 
> Ick, no, never put #ifdef in .c code if you can help it.  For stuff like
> this, just rely on the dynamic debug core and use the pr_debug and
> dev_dbg() calls, like the driver is doing, so all should be fine.
>

But how about those cases where debug code consists of more than a
simple call to pr_debug() / dev_dbg()?

For instance consider dump_eth_packet(), defined in gdm_wimax.c. This
function is called every time a packet is received or transmitted, and
calls other helper functions too (get_protocol_name(),
get_ip_protocol_name(), get_port_name()).

Doesn't all this debug logic provide an overhead to the tx / rx functions?

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