linux-kernel - Re: [PATCH v4 1/5] sched/topology: Add check to backup comment about hotplug lock

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Message-ID: <20180614093324.7ea45448@gandalf.local.home>
Date:   Thu, 14 Jun 2018 09:33:24 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Juri Lelli <juri.lelli@...hat.com>
Cc:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org, luca.abeni@...tannapisa.it,
        claudio@...dence.eu.com, tommaso.cucinotta@...tannapisa.it,
        bristot@...hat.com, mathieu.poirier@...aro.org, lizefan@...wei.com,
        cgroups@...r.kernel.org
Subject: Re: [PATCH v4 1/5] sched/topology: Add check to backup comment
 about hotplug lock

On Wed, 13 Jun 2018 14:17:07 +0200
Juri Lelli <juri.lelli@...hat.com> wrote:

> From: Mathieu Poirier <mathieu.poirier@...aro.org>
> 
> The comment above function partition_sched_domains() clearly state that
> the cpu_hotplug_lock should be held but doesn't mandate one to abide to
> it.
> 
> Add an explicit check backing that comment, so to make it impossible
> for anyone to miss the requirement.
> 
> Suggested-by: Juri Lelli <juri.lelli@...hat.com>
> Signed-off-by: Mathieu Poirier <mathieu.poirier@...aro.org>
> [modified changelog]
> Signed-off-by: Juri Lelli <juri.lelli@...hat.com>

Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve

> ---
>  kernel/sched/topology.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 61a1125c1ae4..96eee22fafe8 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1858,6 +1858,7 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[],
>  	int i, j, n;
>  	int new_topology;
>  
> +	lockdep_assert_cpus_held();
>  	mutex_lock(&sched_domains_mutex);
>  
>  	/* Always unregister in case we don't destroy any domains: */