On Mon, Jul 23, 2018 at 01:49:39PM -0400, Waiman Long wrote: > drivers/cpufreq/cpufreq.c | 16 +++++++++++++++- > 1 file changed, 15 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c > index b0dfd32..9cf02d7 100644 > --- a/drivers/cpufreq/cpufreq.c > +++ b/drivers/cpufreq/cpufreq.c > @@ -922,8 +922,22 @@ static ssize_t store(struct kobject *kobj, struct > attribute *attr, > struct cpufreq_policy *policy = to_policy(kobj); > struct freq_attr *fattr = to_attr(attr); > ssize_t ret = -EINVAL; > + int retries = 3; > > - cpus_read_lock(); > + /* > + * cpus_read_trylock() is used here to work around a circular lock > + * dependency problem with respect to the cpufreq_register_driver(). > + * With a simple retry loop, the chance of not able to get the > + * read lock is extremely small. > + */ > + while (!cpus_read_trylock()) { > + if (retries-- <= 0) > + return -EBUSY; > + /* > + * Sleep for about 50ms and retry again. > + */ > + msleep(50); > + }
That's atrocious.