On 09/20/2013 10:37 PM, Viresh Kumar wrote:
> cpufreq_get() can be called from external drivers which might not be aware if
> cpufreq driver is registered or not. And so we should actually check if cpufreq
> driver is registered or not and also if cpufreq is active or disabled, at the
> beginning of cpufreq_get().
>
> Otherwise call to lock_policy_rwsem_read() might hit BUG_ON(!policy).
>
> Reported-and-Tested-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@xxxxxxxxxxxxxxxxxx>
Regards,
Srivatsa S. Bhat
>
> For 3.12.
>
> drivers/cpufreq/cpufreq.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c
> index 82ecbe3..db004a8 100644
> --- a/drivers/cpufreq/cpufreq.c
> +++ b/drivers/cpufreq/cpufreq.c
> @@ -1460,6 +1460,9 @@ unsigned int cpufreq_get(unsigned int cpu)
> {
> unsigned int ret_freq = 0;
>
> + if (cpufreq_disabled() || !cpufreq_driver)
> + return -ENOENT;
> +
> if (!down_read_trylock(&cpufreq_rwsem))
> return 0;
>
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