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SubjectRe: [PATCH v4 2/5] sched/topology: Adding function partition_sched_domains_locked()
On Wed, 13 Jun 2018 14:17:08 +0200
Juri Lelli <juri.lelli@redhat.com> wrote:

> From: Mathieu Poirier <mathieu.poirier@linaro.org>
>
> Introducing function partition_sched_domains_locked() by taking
> the mutex locking code out of the original function. That way
> the work done by partition_sched_domains_locked() can be reused
> without dropping the mutex lock.
>
> No change of functionality is introduced by this patch.
>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> ---
> include/linux/sched/topology.h | 10 ++++++++++
> kernel/sched/topology.c | 18 ++++++++++++++----
> 2 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index 26347741ba50..57997caf61b6 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -162,6 +162,10 @@ static inline struct cpumask *sched_domain_span(struct sched_domain *sd)
> return to_cpumask(sd->span);
> }
>
> +extern void partition_sched_domains_locked(int ndoms_new,
> + cpumask_var_t doms_new[],
> + struct sched_domain_attr *dattr_new);
> +
> extern void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
> struct sched_domain_attr *dattr_new);
>
> @@ -206,6 +210,12 @@ extern void set_sched_topology(struct sched_domain_topology_level *tl);
>
> struct sched_domain_attr;
>
> +static inline void
> +partition_sched_domains_locked(int ndoms_new, cpumask_var_t doms_new[],
> + struct sched_domain_attr *dattr_new)
> +{
> +}
> +
> static inline void
> partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
> struct sched_domain_attr *dattr_new)
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 96eee22fafe8..25a5727d3b48 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1850,16 +1850,16 @@ static int dattrs_equal(struct sched_domain_attr *cur, int idx_cur,
> * ndoms_new == 0 is a special case for destroying existing domains,
> * and it will not create the default domain.
> *
> - * Call with hotplug lock held
> + * Call with hotplug lock and sched_domains_mutex held
> */
> -void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
> - struct sched_domain_attr *dattr_new)
> +void partition_sched_domains_locked(int ndoms_new, cpumask_var_t doms_new[],
> + struct sched_domain_attr *dattr_new)
> {
> int i, j, n;
> int new_topology;
>
> lockdep_assert_cpus_held();
> - mutex_lock(&sched_domains_mutex);
> + lockdep_assert_held(&sched_domains_mutex);
>
> /* Always unregister in case we don't destroy any domains: */
> unregister_sched_domain_sysctl();
> @@ -1924,6 +1924,16 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
> ndoms_cur = ndoms_new;
>
> register_sched_domain_sysctl();
> +}
>
> +/*
> + * Call with hotplug lock held
> + */
> +void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
> + struct sched_domain_attr *dattr_new)
> +{
> + lockdep_assert_cpus_held();

Is the above assert really necessary? The assert will happen in
partition_sched_domains_locked() anyway.

-- Steve

> + mutex_lock(&sched_domains_mutex);
> + partition_sched_domains_locked(ndoms_new, doms_new, dattr_new);
> mutex_unlock(&sched_domains_mutex);
> }

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