Re: [PATCH] perf tools: Work around lack of sched_getcpu in glibc < 2.6.

[Yann Droneaud <ydroneaud@opteya.com>]

Hi,

Le vendredi 13 février 2015 à 18:06 -0800, Vinson Lee a écrit :
> From: Vinson Lee <vlee@twitter.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@vger.kernel.org # 3.18+
> Signed-off-by: Vinson Lee <vlee@twitter.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@opteya.com>

Regards.

-- 
Yann Droneaud
OPTEYA