On 06/08/21 10:44, Paul E. McKenney wrote: > On Fri, Aug 06, 2021 at 10:04:55AM +0200, Sebastian Andrzej Siewior wrote: > > On 2021-08-05 09:03:37 [-0700], Paul E. McKenney wrote: > > > Makes sense to me! > > > > > > But would another of the -rt people be willing to give an Acked-by? > > > For example, maybe they would prefer this kernel boot parameter to be > > > exposed only if (!PREEMPT_RT || NO_HZ_FULL). Or are there !NO_HZ_FULL > > > situations where rcu_normal_after_boot makes sense? > > > > Julia crafted that "rcu_normal_after_boot = 1" for RT after we had more > > and more synchronize_rcu_expedited() users popping up. I would like to > > keep that part (default value) since it good to have for most users. > > > > I don't mind removing CONFIG_PREEMPT_RT part here if there are legitimate > > use cases for using "rcu_normal_after_boot = 0". > > Paul suggested initially to restrict that option for PREEMPT_RT and I > > would follow here Paul's guidance to either remove it or restrict it to > > NO_HZ_FULL in RT's case (as suggested). > > Given what I know now, I suggest the following: > > o Restrict the option to !PREEMPT_RT unless NO_HZ_FULL. > Maybe "!defined(CONFIG_PREEMPT_RT) || defined(CONFIG_NO_HZ_FULL)". > > If there is some non-NO_HZ_FULL PREEMPT_RT configuration that > tolerates expedited grace periods, this would need to change. > > o Change the permissions from "0" to "0444", if desired. If you > would rather not, I can do this in a follow-up patch. (No idea > why I let such an ugly serviceability issue through, but the > previous pair of module_param() instances have the same problem.) > > Anything I am missing? Not that I can think of right now. :) Will implement your suggestions and submit v2 soon. Thank again to you and Sebastian for the review! Best, Juri
