Messages in this thread | | | Date | Fri, 20 Sep 2013 20:46:21 +0530 | From | "Srivatsa S. Bhat" <> | Subject | Re: Regression on cpufreq in v3.12-rc1 |
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On 09/20/2013 03:05 PM, Viresh Kumar wrote: > On 20 September 2013 14:19, Viresh Kumar <viresh.kumar@linaro.org> wrote: >> Hmm... Remember I told you last time that I have another way of fixing >> it up, probably we need that now.. >> >> I wanted to add another variable to reflect if a cpufreq_driver is registered >> or not, and if not then return early from these routines.. >> >> I will get that in now, please see if you can give it a try.. >> >> But I am still surprised how are we reaching this place before your cpufreq >> driver gets registered.. > > Once we know what's going on in your system, please test attached patch > (Will send it separately once you have tested it): > > commit 389fbc3c8ad7c339cd2d9572d73c355b7b967823 > Author: Viresh Kumar <viresh.kumar@linaro.org> > Date: Fri Sep 20 14:55:31 2013 +0530 > > cpufreq: check cpufreq driver is valid and cpufreq isn't disabled > in cpufreq_get() > > 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). > > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
The patch looks reasonable to me. Earlier cpufreq_cpu_get() used to do the necessary checks, but commit 6eed9404 removed the call to that function in cpufreq_get(). So adding those checks back seem like the right fix to me. Also, looking at commit 6eed9404, I think show() and store() also suffer from a similar fate. So do you think we need to add these checks there as well? I'm not sure, since I can't think of a situation in which show() or store() can be invoked before the cpufreq-driver is registered.. or, is such a situation possible with cpufreq_disabled()?
Regards, Srivatsa S. Bhat
> --- > 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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