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@linaro.org Signed-off-by: Viresh Kumar viresh.kumar@linaro.org

---

Reviewed-by: Srivatsa S. Bhat srivatsa.bhat@linux.vnet.ibm.com

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;