linux-kernel - Re: [PATCH v2 2/8] sched/topology: Wrappers for sched_domains

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Message-ID: <Z8sX5VtKuBD1BoiB@jlelli-thinkpadt14gen4.remote.csb>
Date: Fri, 7 Mar 2025 15:59:33 +0000
From: Juri Lelli <juri.lelli@...hat.com>
To: Waiman Long <llong@...hat.com>
Cc: linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	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 v2 2/8] sched/topology: Wrappers for sched_domains_mutex

On 07/03/25 10:19, Waiman Long wrote:
> 
> On 3/7/25 10:11 AM, Waiman Long wrote:
> > On 3/6/25 9:10 AM, Juri Lelli wrote:
> > > Create wrappers for sched_domains_mutex so that it can transparently be
> > > used on both CONFIG_SMP and !CONFIG_SMP, as some function will need to
> > > do.
> > > 
> > > Reported-by: Jon Hunter <jonathanh@...dia.com>
> > > Fixes: 53916d5fd3c0 ("sched/deadline: Check bandwidth overflow
> > > earlier for hotplug")
> > > Signed-off-by: Juri Lelli <juri.lelli@...hat.com>
> > > ---
> > > v1 -> v2: Remove wrappers for the !SMP case as all users are not defined
> > >            either in that case
> > > ---
> > >   include/linux/sched.h   |  2 ++
> > >   kernel/cgroup/cpuset.c  |  4 ++--
> > >   kernel/sched/core.c     |  4 ++--
> > >   kernel/sched/debug.c    |  8 ++++----
> > >   kernel/sched/topology.c | 12 ++++++++++--
> > >   5 files changed, 20 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > > index 9632e3318e0d..d5f8c161d852 100644
> > > --- a/include/linux/sched.h
> > > +++ b/include/linux/sched.h
> > > @@ -383,6 +383,8 @@ enum uclamp_id {
> > >   extern struct root_domain def_root_domain;
> > >   extern struct mutex sched_domains_mutex;
> > >   #endif
> > > +extern void sched_domains_mutex_lock(void);
> > > +extern void sched_domains_mutex_unlock(void);
> > 
> > As discussed in the other thread, move the
> > sched_domains_mutex_{lock/unlock}{} inside the "#if CONFIG_SMP" block
> > and define the else part so that it can be used in code block that will
> > also be compiled in the !CONFIG_SMP case.
> > 
> > Other than that, the rest looks good to me.
> 
> Actually, you can also remove sched_domains_mutex from the header and make
> it static as it is no longer directly accessed.

Apart from a lockdep_assert_held() in cpuset.c, no? Guess I can create a
wrapper for that, but is it really better?

Thanks,
Juri