linux-kernel - Re: [PATCH] perf tools: rework of handling lack of sched

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Date:	Tue, 19 May 2015 10:49:51 -0300
From:	Arnaldo Carvalho de Melo <acme@...nel.org>
To:	Petr Holasek <pholasek@...hat.com>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>
Subject: Re: [PATCH] perf tools: rework of handling lack of sched_getcpu in
 old glibc

Em Tue, May 19, 2015 at 03:20:47PM +0200, Petr Holasek escreveu:
> Commit e1e455f4f4d3 ("perf tools: Work around lack of sched_getcpu in
> glibc < 2.6.") introduced weak function sched_getcpu() which should
> be overridden by sched_getcpu() provided by glibc >= 2.6. Unfortunately,
> the weak function was linked to sched_getcpu() used in perf bench numa
> and made the benchmark heavily relying on this function unusable.
> 
> This patch alternates weak function magic for preprocessor defines.

With this you break the build again on RHEL5, right? That "fix" was a
quickie, the good thing would be to have this sched_getcpu() thing
somewhere else, far from its user, i.e. cloexec has no business doing
this if there are other places (perf bench numa) that need this, right?

- Arnaldo

 
> Signed-off-by: Petr Holasek <pholasek@...hat.com>
> ---
>  tools/perf/util/cloexec.c | 13 +++++++++++--
>  tools/perf/util/cloexec.h |  6 ------
>  2 files changed, 11 insertions(+), 8 deletions(-)
> 
> diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c
> index 85b5238..23b8aa9 100644
> --- a/tools/perf/util/cloexec.c
> +++ b/tools/perf/util/cloexec.c
> @@ -7,11 +7,20 @@
>  
>  static unsigned long flag = PERF_FLAG_FD_CLOEXEC;
>  
> -int __weak sched_getcpu(void)
> +#ifdef __GLIBC_PREREQ
> +#if !__GLIBC_PREREQ(2, 6)
> +static int do_sched_getcpu(void)
>  {
>  	errno = ENOSYS;
>  	return -1;
>  }
> +#else
> +static int do_sched_getcpu(void)
> +{
> +	return sched_getcpu();
> +}
> +#endif
> +#endif
>  
>  static int perf_flag_probe(void)
>  {
> @@ -27,7 +36,7 @@ static int perf_flag_probe(void)
>  	pid_t pid = -1;
>  	char sbuf[STRERR_BUFSIZE];
>  
> -	cpu = sched_getcpu();
> +	cpu = do_sched_getcpu();
>  	if (cpu < 0)
>  		cpu = 0;
>  
> diff --git a/tools/perf/util/cloexec.h b/tools/perf/util/cloexec.h
> index 68888c2..94a5a7d 100644
> --- a/tools/perf/util/cloexec.h
> +++ b/tools/perf/util/cloexec.h
> @@ -3,10 +3,4 @@
>  
>  unsigned long perf_event_open_cloexec_flag(void);
>  
> -#ifdef __GLIBC_PREREQ
> -#if !__GLIBC_PREREQ(2, 6)
> -extern int sched_getcpu(void) __THROW;
> -#endif
> -#endif
> -
>  #endif /* __PERF_CLOEXEC_H */
> -- 
> 2.1.0
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