linux-kernel - Re: [PATCH] sched/topology: Switch to sched_debug() for conditional sched domain printk

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Date:   Wed, 3 Feb 2021 18:10:19 +0800
From:   Yue Hu <zbestahu@...il.com>
To:     Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
Cc:     mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, linux-kernel@...r.kernel.org,
        huyue2@...ong.com, zbestahu@....com
Subject: Re: [PATCH] sched/topology: Switch to sched_debug() for conditional
 sched domain printk

On Wed, 3 Feb 2021 15:22:56 +0530
Srikar Dronamraju <srikar@...ux.vnet.ibm.com> wrote:

> * Yue Hu <zbestahu@...il.com> [2021-02-03 12:20:10]:
> 
> > From: Yue Hu <huyue2@...ong.com>
> > 
> > Currently, the macro sched_debug_enabled has same function as
> > sched_debug() with return false for !SCHED_DEBUG. And sched_debug()
> > is a wapper of variable sched_debug_enabled for SCHED_DEBUG. We
> > can use the sched_debug() for all cases. So, let's remove the
> > unnecessary marco, also use sched_debug() in sched_domain_debug()
> > for code consistency.
> > 
> > Signed-off-by: Yue Hu <huyue2@...ong.com>
> > ---
> >  kernel/sched/topology.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> > 
> > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> > index 5d3675c..402138c 100644
> > --- a/kernel/sched/topology.c
> > +++ b/kernel/sched/topology.c
> > @@ -131,7 +131,7 @@ static void sched_domain_debug(struct
> > sched_domain *sd, int cpu) {
> >  	int level = 0;
> >  
> > -	if (!sched_debug_enabled)
> > +	if (!sched_debug())
> >  		return;
> >    
> 
> sched_debug() would only be present in CONFIG_SCHED_DEBUG. Right?
> In which case there would be a build failure with your change in
> !CONFIG_SCHED_DEBUG config.
> 
> or Am I missing something?

sched_debug() is also defined for !CONFIG_SCHED_DEBUG as below:

static inline bool sched_debug(void)
{
	return false;
}

And I think define sched_debug() above is just to avoid
CONFIG_SCHED_DEBUG wrappery.

> 
> >  	if (!sd) {
> > @@ -152,7 +152,6 @@ static void sched_domain_debug(struct
> > sched_domain *sd, int cpu) }
> >  #else /* !CONFIG_SCHED_DEBUG */
> >  
> > -# define sched_debug_enabled 0
> >  # define sched_domain_debug(sd, cpu) do { } while (0)
> >  static inline bool sched_debug(void)
> >  {
> > @@ -2113,7 +2112,7 @@ static bool topology_span_sane(struct
> > sched_domain_topology_level *tl, if (has_asym)
> >  		static_branch_inc_cpuslocked(&sched_asym_cpucapacity);
> >  
> > -	if (rq && sched_debug_enabled) {
> > +	if (rq && sched_debug()) {  
> 
> Same as above.
> 
> >  		pr_info("root domain span: %*pbl (max cpu_capacity
> > = %lu)\n", cpumask_pr_args(cpu_map), rq->rd->max_cpu_capacity);
> >  	}
> > -- 
> > 1.9.1
> >   
>