linux-kernel - Re: [PATCH 2/4] perf tools: Introduce cpu_map__snprint

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Date:   Wed, 1 Mar 2017 23:58:33 +0900
From:   Namhyung Kim <namhyung@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, kernel-team@....com,
        Steven Rostedt <rostedt@...dmis.org>,
        Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [PATCH 2/4] perf tools: Introduce cpu_map__snprint_mask()

Hi Arnaldo,

On Sat, Feb 25, 2017 at 1:27 PM, Namhyung Kim <namhyung@...nel.org> wrote:
> Hi Arnaldo,
>
> On Fri, Feb 24, 2017 at 06:08:53PM -0300, Arnaldo Carvalho de Melo wrote:
>> Em Fri, Feb 24, 2017 at 10:12:49AM +0900, Namhyung Kim escreveu:
>> > The cpu_map__snprint_mask() is to generate string representation of
>> > cpumask bitmap.  For cpu 0 to 11, it'll return "fff".
>> >
>> > Cc: Steven Rostedt <rostedt@...dmis.org>
>> > Cc: Frederic Weisbecker <fweisbec@...il.com>
>> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
>> > ---
>> >  tools/perf/util/cpumap.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>> >  tools/perf/util/cpumap.h |  1 +
>> >  2 files changed, 47 insertions(+)
>> >
>> > diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
>> > index 8c7504939113..08540ab2a891 100644
>> > --- a/tools/perf/util/cpumap.c
>> > +++ b/tools/perf/util/cpumap.c
>> > @@ -673,3 +673,49 @@ size_t cpu_map__snprint(struct cpu_map *map, char *buf, size_t size)
>> >     pr_debug("cpumask list: %s\n", buf);
>> >     return ret;
>> >  }
>> > +
>> > +static char hex_char(char val)
>>
>> Why do you use 'char' above and...
>
> My bad.  The argument should be unsigned.  The semantics is that it
> converts a bitmap value into a character (string).
>
>>
>> > +{
>> > +   if (0 <= val && val <= 9)
>> > +           return val + '0';
>> > +   if (10 <= val && val < 16)
>> > +           return val - 10 + 'a';
>> > +   return '?';
>> > +}
>> > +size_t cpu_map__snprint_mask(struct cpu_map *map, char *buf, size_t size)
>> <SNIP>
>> > +   for (cpu = last_cpu / 4 * 4; cpu >= 0; cpu -= 4) {
>> > +           unsigned char bits = bitmap[cpu / 8];
>>
>> 'unsigned char' here?
>>
>> Some compilers don't like it, for instance:
>>
>>   19 fedora:24-x-ARC-uClibc: FAIL
>>
>>   CC       /tmp/build/perf/util/cpumap.o
>> util/cpumap.c: In function 'hex_char':
>> util/cpumap.c:679:2: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>>   if (0 <= val && val <= 9)
>>   ^
>> cc1: all warnings being treated as errors
>>
>> And:
>>
>>   10 debian:experimental-x-arm64: FAIL
>>
>>   CC       /tmp/build/perf/util/cpumap.o
>> util/cpumap.c: In function 'hex_char':
>> util/cpumap.c:679:8: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>>   if (0 <= val && val <= 9)
>>         ^~
>>
>> Are you ok with the patch below?
>
> I'd rather change hex_char() instead.  How about this?
>
> diff --git a/tools/perf/util/cpumap.c b/tools/perf/util/cpumap.c
> index 6ab8699f0233..061018b42393 100644
> --- a/tools/perf/util/cpumap.c
> +++ b/tools/perf/util/cpumap.c
> @@ -674,11 +674,11 @@ size_t cpu_map__snprint(struct cpu_map *map, char *buf, size_t size)
>         return ret;
>  }
>
> -static char hex_char(char val)
> +static char hex_char(unsigned char val)
>  {
> -       if (0 <= val && val <= 9)
> +       if (val < 10)
>                 return val + '0';
> -       if (10 <= val && val < 16)
> +       if (val < 16)
>                 return val - 10 + 'a';
>         return '?';
>  }
>

Ping!

Thanks,
Namhyung