* [PATCH] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks
@ 2019-11-02 0:14 Valentin Schneider
2019-11-03 19:09 ` Ingo Molnar
0 siblings, 1 reply; 3+ messages in thread
From: Valentin Schneider @ 2019-11-02 0:14 UTC (permalink / raw)
To: linux-kernel, cgroups
Cc: lizefan, tj, hannes, mingo, peterz, vincent.guittot,
Dietmar.Eggemann, morten.rasmussen, qperret, Michal Koutný
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@suse.com>
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
---
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
@@ -798,9 +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 */
--
2.22.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks
2019-11-02 0:14 [PATCH] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks Valentin Schneider
@ 2019-11-03 19:09 ` Ingo Molnar
2019-11-04 0:37 ` Valentin Schneider
0 siblings, 1 reply; 3+ messages in thread
From: Ingo Molnar @ 2019-11-03 19:09 UTC (permalink / raw)
To: Valentin Schneider
Cc: linux-kernel, cgroups, lizefan, tj, hannes, peterz,
vincent.guittot, Dietmar.Eggemann, morten.rasmussen, qperret,
Michal Koutný
* Valentin Schneider <valentin.schneider@arm.com> 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@suse.com>
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
> ---
> 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
> @@ -798,9 +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;
This patch doesn't apply cleanly to Linus's latest tree - which tree is
this against?
Thanks,
Ingo
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks
2019-11-03 19:09 ` Ingo Molnar
@ 2019-11-04 0:37 ` Valentin Schneider
0 siblings, 0 replies; 3+ messages in thread
From: Valentin Schneider @ 2019-11-04 0:37 UTC (permalink / raw)
To: Ingo Molnar
Cc: linux-kernel, cgroups, lizefan, tj, hannes, peterz,
vincent.guittot, Dietmar.Eggemann, morten.rasmussen, qperret,
Michal Koutný
On 03/11/2019 19:09, Ingo Molnar wrote:
> This patch doesn't apply cleanly to Linus's latest tree - which tree is
> this against?
>
This was against Linus' tree at the time (31408fbe33d1), but my local .patch
doesn't apply either. I regenerated a fresh one and there's an off-by-one in
original chunk size - I suspect my editor trying to be smart when I edited
the changelog.
I'll look into preventing this from happening again, in the meantime I'll
send an apply-able version. Apologies for that mess.
> Thanks,
>
> Ingo
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-11-02 0:14 [PATCH] sched/topology, cpuset: Account for housekeeping CPUs to avoid empty cpumasks Valentin Schneider
2019-11-03 19:09 ` Ingo Molnar
2019-11-04 0:37 ` Valentin Schneider
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