linux-kernel - Re: [PATCH] perf tools: Work around lack of sched

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Date:	Tue, 17 Mar 2015 16:49:13 -0700
From:	Vinson Lee <vlee@...pensource.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Jiri Olsa <jolsa@...hat.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org, Vinson Lee <vlee@...tter.com>,
	Yann Droneaud <ydroneaud@...eya.com>
Subject: Re: [PATCH] perf tools: Work around lack of sched_getcpu in glibc < 2.6.

On Mon, Feb 16, 2015 at 12:50 PM, Yann Droneaud <ydroneaud@...eya.com> wrote:
> Hi,
>
> Le vendredi 13 février 2015 à 18:06 -0800, Vinson Lee a écrit :
>> From: Vinson Lee <vlee@...tter.com>
>>
>> This patch fixes this build error with glibc < 2.6.
>>
>>   CC       util/cloexec.o
>> cc1: warnings being treated as errors
>> util/cloexec.c: In function ‘perf_flag_probe’:
>> util/cloexec.c:24: error: implicit declaration of function
>> ‘sched_getcpu’
>> util/cloexec.c:24: error: nested extern declaration of ‘sched_getcpu’
>> make: *** [util/cloexec.o] Error 1
>>
>> Cc: stable@...r.kernel.org # 3.18+
>> Signed-off-by: Vinson Lee <vlee@...tter.com>
>> ---
>>  tools/perf/util/cloexec.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>>
>> diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
>> index 47b78b3..3738924 100644
>> --- a/tools/perf/util/cloexec.c
>> +++ b/tools/perf/util/cloexec.c
>> @@ -7,6 +7,12 @@
>>
>>  static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
>>
>> +#ifdef __GLIBC_PREREQ
>> +#if __GLIBC_PREREQ(2, 6)
>> +#define HAVE_SCHED_GETCPU
>> +#endif
>> +#endif
>> +
>
> OK
>
>>  static int perf_flag_probe(void)
>>  {
>>       /* use 'safest' configuration as used in perf_evsel__fallback() */
>> @@ -21,9 +27,13 @@ static int perf_flag_probe(void)
>>       pid_t pid = -1;
>>       char sbuf[STRERR_BUFSIZE];
>>
>> +#ifdef HAVE_SCHED_GETCPU
>>       cpu = sched_getcpu();
>>       if (cpu < 0)
>>               cpu = 0;
>> +#else
>> +     cpu = 0;
>> +#endif
>>
>>       while (1) {
>>               /* check cloexec flag */
>
> I've reviewed the use of __GLIBC_PREREQ(2, 6), but not whether using cpu
> = 0 is OK if sched_getcpu() is not available.
>
> Reviewed-by: Yann Droneaud <ydroneaud@...eya.com>
>
> Regards.
>
> --
> Yann Droneaud
> OPTEYA
>
>
>

Ping. Please review the sched_getcpu hunk.
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