Re: [Xen-devel] [PATCH 3/3] tools: sched: add support for 'null' scheduler

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 17/03/17 18:43, Dario Faggioli wrote:
> It being very very basic, also means this scheduler does
> not need much support at the tools level (for now).
> 
> Basically, just the definition of the symbol of the
> scheduler itself and a couple of stubs.
> 
> Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
> ---
> Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
> Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
> Cc: George Dunlap <george.dunlap@xxxxxxxxxx>
> Cc: Stefano Stabellini <stefano@xxxxxxxxxxx>
> Cc: Julien Grall <julien.grall@xxxxxxx>
> ---
>  tools/libxl/libxl.h         |    6 ++++++
>  tools/libxl/libxl_sched.c   |   24 ++++++++++++++++++++++++
>  tools/libxl/libxl_types.idl |    1 +
>  3 files changed, 31 insertions(+)
> 
> diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
> index 4c60e8f..5adac2d 100644
> --- a/tools/libxl/libxl.h
> +++ b/tools/libxl/libxl.h
> @@ -210,6 +210,12 @@
>  #define LIBXL_HAVE_SCHED_RTDS 1
>  
>  /*
> + * LIBXL_HAVE_SCHED_NULL indicates that the 'null' static scheduler
> + * is available.
> + */
> +#define LIBXL_HAVE_SCHED_NULL 1
> +
> +/*
>   * libxl_domain_build_info has u.hvm.viridian_enable and _disable bitmaps
>   * of the specified width.
>   */
> diff --git a/tools/libxl/libxl_sched.c b/tools/libxl/libxl_sched.c
> index 84d3837..d44fbe1 100644
> --- a/tools/libxl/libxl_sched.c
> +++ b/tools/libxl/libxl_sched.c
> @@ -178,6 +178,20 @@ static int sched_arinc653_domain_set(libxl__gc *gc, 
> uint32_t domid,
>      return 0;
>  }
>  
> +static int sched_null_domain_set(libxl__gc *gc, uint32_t domid,
> +                                 const libxl_domain_sched_params *scinfo)
> +{
> +    /* The null scheduler doesn't take any domain-specific parameters. */
> +    return 0;
> +}
> +
> +static int sched_null_domain_get(libxl__gc *gc, uint32_t domid,
> +                               libxl_domain_sched_params *scinfo)
> +{
> +    /* The null scheduler doesn't have any domain-specific parameters. */
> +    return ERROR_INVAL;
> +}

Why the different return value?  Why not return either INVAL or SUCCESS
for both?

 -George


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