[LTP] [PATCH v2 6/7] API: Add tst_ncpus_available

[Cyril Hrubis]

Hi!
> Signed-off-by: Richard Palethorpe <rpalethorpe@suse.com>
> ---
>  include/tst_cpu.h |  1 +
>  lib/tst_cpu.c     | 23 +++++++++++++++++++++++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/include/tst_cpu.h b/include/tst_cpu.h
> index 117e27087..b3a449bea 100644
> --- a/include/tst_cpu.h
> +++ b/include/tst_cpu.h
> @@ -8,6 +8,7 @@
>  long tst_ncpus(void);
>  long tst_ncpus_conf(void);
>  long tst_ncpus_max(void);
> +long tst_ncpus_available(void);
>  
>  #define VIRT_ANY	0	/* catch-all argument for tst_is_virt() */
>  #define VIRT_XEN	1	/* xen dom0/domU */
> diff --git a/lib/tst_cpu.c b/lib/tst_cpu.c
> index 033155e47..581215199 100644
> --- a/lib/tst_cpu.c
> +++ b/lib/tst_cpu.c
> @@ -17,6 +17,8 @@
>   *   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
>   */
>  
> +#include "lapi/cpuset.h"
> +
>  #include <stdlib.h>
>  #include <unistd.h>
>  #include "test.h"
> @@ -71,3 +73,24 @@ long tst_ncpus_max(void)
>  	}
>  	return ncpus_max;
>  }
> +
> +long tst_ncpus_available(void)
> +{
> +#ifdef CPU_COUNT
> +	long ncpus = tst_ncpus_max();
> +	size_t cpusz = CPU_ALLOC_SIZE(ncpus);
> +	cpu_set_t *cpus = CPU_ALLOC(ncpus);


The CPU_ALLOC() is allowed to fail an return NULL, I guess that the
worst that would happen here is EFAULT from sched_getaffinity() but it
would be nicer to do something as:

	if (!cpus) {
		tst_resm(TWARN | TERRNO, "CPU_ALLOC() failed");
		return ncpus;
	}

> +	if (sched_getaffinity(0, cpusz, cpus)) {
> +		tst_resm(TWARN | TERRNO, "sched_getaffinity(0, %zu, %zx)",
> +			cpusz, (size_t)cpus);
> +	} else {
> +		ncpus = CPU_COUNT(cpus);
> +	}
> +	free(cpus);

This should be CPU_FREE() if we are pedantic.

I guess that nothing stops glibc from using alloca() if we have less
than a few bytes to allocate and switch to malloc() only if the ncpus is
bigger than certain threshold internally in the CPU_ALLOC() macro.

> +	return ncpus;
> +#else
> +	return tst_ncpus();
> +#endif
> +}
> -- 
> 2.30.1
> 
> 
> -- 
> Mailing list info: https://lists.linux.it/listinfo/ltp

-- 
Cyril Hrubis
chrubis@suse.cz