On 04/11/2019 00:39, Valentin Schneider wrote:
> Michal noted that a cpuset's effective_cpus can be a non-empy mask, but
> because of the masking done with housekeeping_cpumask(HK_FLAG_DOMAIN)
> further down the line, we can still end up with an empty cpumask being
> passed down to partition_sched_domains_locked().
>
> Do the proper thing and don't just check the mask is non-empty - check
> that its intersection with housekeeping_cpumask(HK_FLAG_DOMAIN) is
> non-empty.
>
> Fixes: cd1cb3350561 ("sched/topology: Don't try to build empty sched domains")
> Reported-by: Michal Koutný <mkoutny@xxxxxxxx>
> Signed-off-by: Valentin Schneider <valentin.schneider@xxxxxxx>
> ---
Sigh, this is missing:
v2 changes:
- Fix broken diff
At least it *does* apply this time around.
> kernel/cgroup/cpuset.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index c87ee6412b36..e4c10785dc7c 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -798,8 +798,14 @@ static int generate_sched_domains(cpumask_var_t **domains,
> cpumask_subset(cp->cpus_allowed, top_cpuset.effective_cpus))
> continue;
>
> + /*
> + * Skip cpusets that would lead to an empty sched domain.
> + * That could be because effective_cpus is empty, or because
> + * it's only spanning CPUs outside the housekeeping mask.
> + */
> if (is_sched_load_balance(cp) &&
> - !cpumask_empty(cp->effective_cpus))
> + cpumask_intersects(cp->effective_cpus,
> + housekeeping_cpumask(HK_FLAG_DOMAIN)))
> csa[csn++] = cp;
>
> /* skip @cp's subtree if not a partition root */
>
