linux-kernel - Re: [PATCH 2/5] sched/topology: Wrappers for sched_domains

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Message-ID: <0abc29ee-df9c-4c00-a7f9-d55ab5dd90c4@redhat.com>
Date: Tue, 4 Mar 2025 11:01:08 -0500
From: Waiman Long <llong@...hat.com>
To: Juri Lelli <juri.lelli@...hat.com>, linux-kernel@...r.kernel.org,
 cgroups@...r.kernel.org
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>,
 Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
 Michal Koutný <mkoutny@...e.com>,
 Qais Yousef <qyousef@...alina.io>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Swapnil Sapkal <swapnil.sapkal@....com>,
 Shrikanth Hegde <sshegde@...ux.ibm.com>, Phil Auld <pauld@...hat.com>,
 luca.abeni@...tannapisa.it, tommaso.cucinotta@...tannapisa.it,
 Jon Hunter <jonathanh@...dia.com>
Subject: Re: [PATCH 2/5] sched/topology: Wrappers for sched_domains_mutex

On 3/4/25 10:05 AM, Waiman Long wrote:
>> --- a/kernel/sched/topology.c
>> +++ b/kernel/sched/topology.c
>> @@ -6,6 +6,19 @@
>>   #include <linux/bsearch.h>
>>     DEFINE_MUTEX(sched_domains_mutex);
>> +#ifdef CONFIG_SMP
>> +void sched_domains_mutex_lock(void)
>> +{
>> +    mutex_lock(&sched_domains_mutex);
>> +}
>> +void sched_domains_mutex_unlock(void)
>> +{
>> +    mutex_unlock(&sched_domains_mutex);
>> +}
>> +#else
>> +void sched_domains_mutex_lock(void) { }
>> +void sched_domains_mutex_unlock(void) { }
>> +#endif
>>     /* Protected by sched_domains_mutex: */
>>   static cpumask_var_t sched_domains_tmpmask;
>> @@ -2791,7 +2804,7 @@ void partition_sched_domains_locked(int 
>> ndoms_new, cpumask_var_t doms_new[],
>>   void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
>>                    struct sched_domain_attr *dattr_new)
>>   {
>> -    mutex_lock(&sched_domains_mutex);
>> +    sched_domains_mutex_lock();
>>       partition_sched_domains_locked(ndoms_new, doms_new, dattr_new);
>> -    mutex_unlock(&sched_domains_mutex);
>> +    sched_domains_mutex_unlock();
>>   }
>
> There are two "lockdep_assert_held(&sched_domains_mutex);" statements 
> in topology.c file and one in cpuset.c. That can be problematic in the 
> non-SMP case. Maybe another wrapper to do the assert?

Ignore that as both topology.c and cpuset.c will only be compiled if 
CONFIG_SMP is defined. IOW, you don't need the the "#ifdef CONFIG_SMP" 
above.

Cheers,
Longman