linux-kernel - Re: [PATCH 02/17] tracing/probes: Fix basic print type functions

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Message-ID: <87iovdqaif.fsf@sejong.aot.lge.com>
Date:	Thu, 28 Nov 2013 15:57:12 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Hyeoncheol Lee <cheol.lee@....com>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	"zhangwei\(Jovi\)" <jovi.zhangwei@...wei.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Hemant Kumar <hkshaw@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Namhyung Kim <namhyung.kim@....com>
Subject: Re: [PATCH 02/17] tracing/probes: Fix basic print type functions

Hi Masami,

On Thu, 28 Nov 2013 13:16:09 +0900, Masami Hiramatsu wrote:
> (2013/11/27 23:39), Namhyung Kim wrote:
>> Hi Masami,
>> 
>> 2013-11-27 (수), 20:57 +0900, Masami Hiramatsu:
>>> (2013/11/27 15:19), Namhyung Kim wrote:
>>>>  
>>>> -DEFINE_BASIC_PRINT_TYPE_FUNC(u8, "%x", unsigned int)
>>>> -DEFINE_BASIC_PRINT_TYPE_FUNC(u16, "%x", unsigned int)
>>>> -DEFINE_BASIC_PRINT_TYPE_FUNC(u32, "%lx", unsigned long)
>>>> -DEFINE_BASIC_PRINT_TYPE_FUNC(u64, "%llx", unsigned long long)
>>>> -DEFINE_BASIC_PRINT_TYPE_FUNC(s8, "%d", int)
>>>> -DEFINE_BASIC_PRINT_TYPE_FUNC(s16, "%d", int)
>>>> -DEFINE_BASIC_PRINT_TYPE_FUNC(s32, "%ld", long)
>>>> -DEFINE_BASIC_PRINT_TYPE_FUNC(s64, "%lld", long long)
>>>> +DEFINE_BASIC_PRINT_TYPE_FUNC(u8 , "%#x")
>>>> +DEFINE_BASIC_PRINT_TYPE_FUNC(u16, "%#x")
>>>> +DEFINE_BASIC_PRINT_TYPE_FUNC(u32, "%#x")
>>>> +DEFINE_BASIC_PRINT_TYPE_FUNC(u64, "%#Lx")
>>>
>>> As I said I'd like to ask you to change it in %x.
>>>
>>> I just checked in Fedora18, but %#x is not supported on this glibc-2.17.
>>> Since this format is exported via debugfs (format file), I think %x is
>>> better.
>> 
>> Hmm.. but in most cases it's used for printf() not scanf(), right?  In
>> that case adding 0x prefix will help human readers a lot.
>> 
>> How about mandating the prefix with "0x%x"?  This way it can be used
>> both for printf() and scanf() IMHO.
>
> Agreed, you can just use "0x%x" in above case instead of "%#x". :)

Okay, will change.


> For other traceevents, from the human readability point of view,
> I think we should move all the event format should use 0x%x instead
> of %x, because sometimes it confuse users (e.g. 100 => 0x64, without 0x,
> it is just "64").

Agreed.  I'll take a look at them later.

Thanks,
Namhyung
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