On Wednesday, December 17, 2014 10:06:17 AM Viresh Kumar wrote: > On 17 December 2014 at 04:39, Dmitry Torokhov <[email protected]> wrote: > > A lot of callers are missing the fact that dev_pm_opp_get_opp_count > > needs to be called under RCU lock. Given that RCU locks can safely be > > nested, instead of providing *_locked() API, let's take RCU lock inside > > Hmm, I asked for a *_locked() API because many users of > dev_pm_opp_get_opp_count() are already calling it from rcu read side > critical sections. > > Now, there are two questions: > - Can rcu-read side critical sections be nested ? > > Yes, this is what the comment over rcu_read_lock() says > > * RCU read-side critical sections may be nested. Any deferred actions > * will be deferred until the outermost RCU read-side critical section > * completes. > > - Would it be better to drop these double rcu_read_locks() ? i.e. either > get a *_locked() API or fix the callers of dev_pm_opp_get_opp_count(). > > @Paul: What do you say ? >
FWIW the change is a stop-gap; I hope we'll get away from using dev_pm_opp_get_opp_count() in cpufreq drivers and then we can revert the change. I just did not want to touch cpufreq drivers unless necessary. Thanks, Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
