linux-kernel - Re: [GIT PULL] scheduler fixes

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Date:   Sat, 2 Nov 2019 01:15:58 +0100
From:   Valentin Schneider <valentin.schneider@....com>
To:     Ingo Molnar <mingo@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [GIT PULL] scheduler fixes

Hi,

On 01/11/2019 18:55, Ingo Molnar wrote:
> Linus,
> 
> Please pull the latest sched-urgent-for-linus git tree from:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-urgent-for-linus
> 
>    # HEAD: e284df705cf1eeedb5ec3a66ed82d17a64659150 sched/topology: Allow sched_asym_cpucapacity to be disabled
> 
> Fix two scheduler topology bugs/oversights on Juno r0 2+4 big.LITTLE 
> systems.
>

I was hoping to fix this up before the PR got out, but as I've been traveling
that didn't happen. FWIW Michal spotted that the empty cpumask fix is not
complete, it also needs to check against the housekeeping cpumask. I've done
that at 20191102001406.10208-1-valentin.schneider@....com.

Sorry about that,
Valentin
 
>  Thanks,
> 
> 	Ingo
> 
> ------------------>
> Valentin Schneider (2):
>       sched/topology: Don't try to build empty sched domains
>       sched/topology: Allow sched_asym_cpucapacity to be disabled
> 
> 
>  kernel/cgroup/cpuset.c  |  3 ++-
>  kernel/sched/topology.c | 11 +++++++++--
>  2 files changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index c52bc91f882b..c87ee6412b36 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -798,7 +798,8 @@ static int generate_sched_domains(cpumask_var_t **domains,
>  		    cpumask_subset(cp->cpus_allowed, top_cpuset.effective_cpus))
>  			continue;
>  
> -		if (is_sched_load_balance(cp))
> +		if (is_sched_load_balance(cp) &&
> +		    !cpumask_empty(cp->effective_cpus))
>  			csa[csn++] = cp;
>  
>  		/* skip @cp's subtree if not a partition root */
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index b5667a273bf6..49b835f1305f 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1948,7 +1948,7 @@ static struct sched_domain_topology_level
>  static int
>  build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *attr)
>  {
> -	enum s_alloc alloc_state;
> +	enum s_alloc alloc_state = sa_none;
>  	struct sched_domain *sd;
>  	struct s_data d;
>  	struct rq *rq = NULL;
> @@ -1956,6 +1956,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
>  	struct sched_domain_topology_level *tl_asym;
>  	bool has_asym = false;
>  
> +	if (WARN_ON(cpumask_empty(cpu_map)))
> +		goto error;
> +
>  	alloc_state = __visit_domain_allocation_hell(&d, cpu_map);
>  	if (alloc_state != sa_rootdomain)
>  		goto error;
> @@ -2026,7 +2029,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
>  	rcu_read_unlock();
>  
>  	if (has_asym)
> -		static_branch_enable_cpuslocked(&sched_asym_cpucapacity);
> +		static_branch_inc_cpuslocked(&sched_asym_cpucapacity);
>  
>  	if (rq && sched_debug_enabled) {
>  		pr_info("root domain span: %*pbl (max cpu_capacity = %lu)\n",
> @@ -2121,8 +2124,12 @@ int sched_init_domains(const struct cpumask *cpu_map)
>   */
>  static void detach_destroy_domains(const struct cpumask *cpu_map)
>  {
> +	unsigned int cpu = cpumask_any(cpu_map);
>  	int i;
>  
> +	if (rcu_access_pointer(per_cpu(sd_asym_cpucapacity, cpu)))
> +		static_branch_dec_cpuslocked(&sched_asym_cpucapacity);
> +
>  	rcu_read_lock();
>  	for_each_cpu(i, cpu_map)
>  		cpu_attach_domain(NULL, &def_root_domain, i);
>