Re: [PATCH 11/12] task_isolation: kick_all_cpus_sync: don't kick isolated cpus

Frederic Weisbecker
2020-03-06T15:34:50Z

On Wed, Mar 04, 2020 at 04:15:24PM +0000, Alex Belits wrote:
> From: Yuri Norov <ynorov@marvell.com>
>
> Make sure that kick_all_cpus_sync() does not call CPUs that are running
> isolated tasks.
>
> Signed-off-by: Alex Belits <abelits@marvell.com>
> ---
> kernel/smp.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/smp.c b/kernel/smp.c
> index 3a8bcbdd4ce6..d9b4b2fedfed 100644
> --- a/kernel/smp.c
> +++ b/kernel/smp.c
> @@ -731,9 +731,21 @@ static void do_nothing(void *unused)
> */
> void kick_all_cpus_sync(void)
> {
> + struct cpumask mask;
> +
> /* Make sure the change is visible before we kick the cpus */
> smp_mb();
> - smp_call_function(do_nothing, NULL, 1);
> +
> + preempt_disable();
> +#ifdef CONFIG_TASK_ISOLATION
> + cpumask_clear(&mask);
> + task_isolation_cpumask(&mask);
> + cpumask_complement(&mask, &mask);
> +#else
> + cpumask_setall(&mask);
> +#endif
> + smp_call_function_many(&mask, do_nothing, NULL, 1);
> + preempt_enable();
> }

That looks very dangerous, the callers of kick_all_cpus_sync() want to
sync all CPUs for a reason. You will rather need to fix the callers.

Thanks.

> EXPORT_SYMBOL_GPL(kick_all_cpus_sync);
>
> --
> 2.20.1
>