linux-kernel - Re: [PATCH] opp: Reduce the size of critical section in _opp_table_kref

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Date:   Thu, 29 Oct 2020 17:38:17 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>
Cc:     linux-pm@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rafael Wysocki <rjw@...ysocki.net>,
        Rob Clark <robdclark@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] opp: Reduce the size of critical section in
 _opp_table_kref_release()

27.10.2020 10:57, Viresh Kumar пишет:
> There is a lot of stuff here which can be done outside of the big
> opp_table_lock, do that. This helps avoiding few circular dependency
> lockdeps around debugfs and interconnects.
> 
> Reported-by: Rob Clark <robdclark@...il.com>
> Reported-by: Dmitry Osipenko <digetx@...il.com>
> Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
> ---
> Rob: I know this only fixes the issue partially for you and I am still
> looking into that. I just wanted to get this merged in early as this
> fixes lockdep for other users as well.
> 
>  drivers/opp/core.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/opp/core.c b/drivers/opp/core.c
> index 4ac4e7ce6b8b..0e0a5269dc82 100644
> --- a/drivers/opp/core.c
> +++ b/drivers/opp/core.c
> @@ -1181,6 +1181,10 @@ static void _opp_table_kref_release(struct kref *kref)
>  	struct opp_device *opp_dev, *temp;
>  	int i;
>  
> +	/* Drop the lock as soon as we can */
> +	list_del(&opp_table->node);
> +	mutex_unlock(&opp_table_lock);
> +
>  	_of_clear_opp_table(opp_table);
>  
>  	/* Release clk */
> @@ -1208,10 +1212,7 @@ static void _opp_table_kref_release(struct kref *kref)
>  
>  	mutex_destroy(&opp_table->genpd_virt_dev_lock);
>  	mutex_destroy(&opp_table->lock);
> -	list_del(&opp_table->node);
>  	kfree(opp_table);
> -
> -	mutex_unlock(&opp_table_lock);
>  }
>  
>  void dev_pm_opp_put_opp_table(struct opp_table *opp_table)
> 

Fixes the NVIDIA Tegra devfreq driver lockup using WIP ICC patches, thanks.

Tested-by: Dmitry Osipenko <digetx@...il.com>