On 03-09-15, 20:11, Bartlomiej Zolnierkiewicz wrote:
> Add dev_pm_opp_get_suspend_opp() helper to obtain suspend opp.
>
> Cc: Viresh Kumar <viresh.ku...@linaro.org>
> Cc: Thomas Abraham <thomas...@samsung.com>
> Cc: Javier Martinez Canillas <jav...@osg.samsung.com>
> Cc: Krzysztof Kozlowski <k.kozlow...@samsung.com>
> Cc: Marek Szyprowski <m.szyprow...@samsung.com>
> Cc: Tobias Jakobi <tjak...@math.uni-bielefeld.de>
> Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnier...@samsung.com>
> ---
> drivers/base/power/opp.c | 28 ++++++++++++++++++++++++++++
> include/linux/pm_opp.h | 6 ++++++
> 2 files changed, 34 insertions(+)
>
> diff --git a/drivers/base/power/opp.c b/drivers/base/power/opp.c
> index eb25449..eaafca7 100644
> --- a/drivers/base/power/opp.c
> +++ b/drivers/base/power/opp.c
> @@ -341,6 +341,34 @@ unsigned long dev_pm_opp_get_max_clock_latency(struct
> device *dev)
> EXPORT_SYMBOL_GPL(dev_pm_opp_get_max_clock_latency);
>
> /**
> + * dev_pm_opp_get_suspend_opp() - Get suspend opp
> + * @dev: device for which we do this operation
> + *
> + * Return: This function returns pointer to the suspend opp if it is
> + * defined, otherwise it returns NULL.
> + *
> + * Locking: This function takes rcu_read_lock().
> + */
> +struct dev_pm_opp *dev_pm_opp_get_suspend_opp(struct device *dev)
> +{
> + struct device_opp *dev_opp;
> + struct dev_pm_opp *suspend_opp;
> +
> + rcu_read_lock();
This is wrong. Please have a look at other exported APIs that return
an OPP. RCU protected structures must be accessed from within RCU
locks _ONLY_. But your function returns the pointer after dropping
the locks. Which essentially means that the OPP can be freed by core,
by the time you start using it. :)
So, in such cases, its upto the caller to ensure that locks are taken
properly.
You can look at dev_pm_opp_find_freq_exact() as an example.
--
viresh
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