linux-kernel - Re: [PATCH] PM / OPP: add some lockdep annotations

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Date:	Tue, 16 Dec 2014 11:01:12 +0530
From:	Viresh Kumar <viresh.kumar@...aro.org>
To:	Dmitry Torokhov <dtor@...omium.org>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Pavel Machek <pavel@....cz>, Len Brown <len.brown@...el.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nishanth Menon <nm@...com>,
	Chander Kashyap <k.chander@...sung.com>,
	Inderpal Singh <inderpal.s@...sung.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PM / OPP: add some lockdep annotations

On 16 December 2014 at 06:12, Dmitry Torokhov <dtor@...omium.org> wrote:
> Certain OPP APIs need to be called under RCU lock; let's add a few
> rcu_lockdep_assert() calls to warn about potential misuse.

Very nice..

> Signed-off-by: Dmitry Torokhov <dtor@...omium.org>
> ---
>  drivers/base/power/opp.c | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
>
> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> index d24dd614a..852eebf 100644
> --- a/drivers/base/power/opp.c
> +++ b/drivers/base/power/opp.c
> @@ -218,6 +218,11 @@ int dev_pm_opp_get_opp_count(struct device *dev)
>         struct dev_pm_opp *temp_opp;
>         int count = 0;
>
> +       rcu_lockdep_assert(rcu_read_lock_held() ||
> +                               lockdep_is_held(&dev_opp_list_lock),
> +                          "dev_pm_opp_get_opp_count() needs rcu_read_lock() "
> +                          "or dev_opp_list_lock protection");
> +
>         dev_opp = find_device_opp(dev);
>         if (IS_ERR(dev_opp)) {
>                 int r = PTR_ERR(dev_opp);
> @@ -267,6 +272,11 @@ struct dev_pm_opp *dev_pm_opp_find_freq_exact(struct device *dev,
>         struct device_opp *dev_opp;
>         struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
>
> +       rcu_lockdep_assert(rcu_read_lock_held() ||
> +                               lockdep_is_held(&dev_opp_list_lock),
> +                          "dev_pm_opp_find_freq_exact() needs rcu_read_lock() "
> +                          "or dev_opp_list_lock protection");
> +
>         dev_opp = find_device_opp(dev);
>         if (IS_ERR(dev_opp)) {
>                 int r = PTR_ERR(dev_opp);
> @@ -313,6 +323,11 @@ struct dev_pm_opp *dev_pm_opp_find_freq_ceil(struct device *dev,
>         struct device_opp *dev_opp;
>         struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
>
> +       rcu_lockdep_assert(rcu_read_lock_held() ||
> +                               lockdep_is_held(&dev_opp_list_lock),
> +                          "dev_pm_opp_find_freq_ceil() needs rcu_read_lock() "
> +                          "or dev_opp_list_lock protection");
> +
>         if (!dev || !freq) {
>                 dev_err(dev, "%s: Invalid argument freq=%p\n", __func__, freq);
>                 return ERR_PTR(-EINVAL);
> @@ -361,6 +376,11 @@ struct dev_pm_opp *dev_pm_opp_find_freq_floor(struct device *dev,
>         struct device_opp *dev_opp;
>         struct dev_pm_opp *temp_opp, *opp = ERR_PTR(-ERANGE);
>
> +       rcu_lockdep_assert(rcu_read_lock_held() ||
> +                               lockdep_is_held(&dev_opp_list_lock),
> +                          "dev_pm_opp_find_freq_floor() needs rcu_read_lock() "
> +                          "or dev_opp_list_lock protection");
> +

To get rid of the redundancy a bit, what about something like:

#define opp_rcu_lockdep_assert()        \
        rcu_lockdep_assert(rcu_read_lock_held() || \
                                        lockdep_is_held(&dev_opp_list_lock), \
                                        "Missing rcu_read_lock() or
dev_opp_list_lock protection");
--
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