On Monday, April 29, 2013 02:37:28 PM Paul E. McKenney wrote: > On Mon, Apr 29, 2013 at 12:22:32AM +0200, Rafael J. Wysocki wrote: > > On Thursday, April 04, 2013 09:57:19 PM Viresh Kumar wrote: > > > On 4 April 2013 20:23, Nathan Zimmer <nzimmer@xxxxxxx> wrote: > > > > We eventually would like to remove the rwlock cpufreq_driver_lock or convert > > > > it back to a spinlock and protect the read sections with RCU. The first step in > > > > that is moving the cpufreq_driver to use the rcu. > > > > I don't see an easy wasy to protect the cpufreq_cpu_data structure with the > > > > RCU, so I am leaving it with the rwlock for now since under certain configs > > > > __cpufreq_cpu_get is hot spot with 256+ cores. > > > > > > > > v5: Go a different way and split up the lock and use the rcu > > > > v6: use bools instead of checking function pointers > > > > covert the cpufreq_data_lock to a rwlock > > > > v7: Rebase to use the already accepted half > > > > v8: Correct have_governor_per_policy > > > > Reviewed location of rcu_read_(un)lock in several spots > > > > > > Sorry for long delay or too many versions of this patch :) > > > > > > Acked-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx> > > > > Unfortunately, I had to revert this one, because it is obviously buggy. Why? > > Because it adds rcu_read_lock()/rcu_read_unlock() around sysfs_create_file() > > which may sleep due to a GFP_KERNEL memory allocation. Sorry for failing to > > notice that earlier. > > One workaround might be to use SRCU, which allows sleeping in its > critical sections. Agreed, but at this point of the cycle I'd just preferred to do the revert and start over. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe cpufreq" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
