Re: [PATCH v5 1/2] smpboot: allow excluding cpus from the smpboot threads

Frederic Weisbecker
2015-04-08T13:29:07Z

On Mon, Apr 06, 2015 at 03:45:55PM -0400, cmetcalf@ezchip.com wrote:
> From: Chris Metcalf <cmetcalf@ezchip.com>
>
> This change allows some cores to be excluded from running the
> smp_hotplug_thread tasks. The motivating example for this is
> the watchdog threads, which by default we don't want to run
> on any enabled nohz_full cores.
>
> Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
> ---
> include/linux/smpboot.h | 2 ++
> kernel/smpboot.c | 11 ++++++++---
> 2 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/smpboot.h b/include/linux/smpboot.h
> index d600afb21926..de2f64a98108 100644
> --- a/include/linux/smpboot.h
> +++ b/include/linux/smpboot.h
> @@ -27,6 +27,7 @@ struct smpboot_thread_data;
> * @pre_unpark: Optional unpark function, called before the thread is
> * unparked (cpu online). This is not guaranteed to be
> * called on the target cpu of the thread. Careful!
> + * @exclude_mask: Optional cpumask, specifying cores to exclude.
> * @selfparking: Thread is not parked by the park function.
> * @thread_comm: The base name of the thread
> */
> @@ -41,6 +42,7 @@ struct smp_hotplug_thread {
> void (*park)(unsigned int cpu);
> void (*unpark)(unsigned int cpu);
> void (*pre_unpark)(unsigned int cpu);
> + cpumask_t *exclude_mask;

The usual pattern for cpumasks is to use them as affinity values instead
of non-affinity values.

Thanks.