On Wed, Oct 18, 2023 at 02:00:35PM -0400, Steven Rostedt wrote: > On Wed, 18 Oct 2023 10:55:02 -0700 > "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote: > > > > If everything becomes PREEMPT_RCU, then the above should be able to be > > > turned into just: > > > > > > if (!disable_irq) > > > local_irq_disable(); > > > > > > rcu_momentary_dyntick_idle(); > > > > > > if (!disable_irq) > > > local_irq_enable(); > > > > > > And no cond_resched() is needed. > > > > Even given that CONFIG_PREEMPT_RCU=n still exists, the fact that > > run_osnoise() is running in kthread context with preemption and everything > > else enabled (am I right?), then the change you suggest should work fine. > > There's a user space option that lets you run that loop with preemption and/or > interrupts disabled. Ah, thank you. Then as long as this function is not expecting an RCU reader to span that call to rcu_momentary_dyntick_idle(), all is well. This is a kthread, so there cannot be something else expecting an RCU reader to span that call. > > > > Again. There is no non-preemtible RCU with this model, unless I'm > > > > missing something important here. > > > > > > Daniel? > > > > But very happy to defer to Daniel. ;-) > > But Daniel could also correct me ;-) If he figures out a way that it is broken, he gets to fix it. ;-) Thanx, Paul
