On Wed, 28 Feb 2024 14:19:11 -0800 "Paul E. McKenney" <paulmck@xxxxxxxxxx> wrote: > > > > > > Well, to your initial point, cond_resched() does eventually invoke > > > preempt_schedule_common(), so you are quite correct that as far as > > > Tasks RCU is concerned, cond_resched() is not a quiescent state. > > > > Thanks for confirming. :-) > > However, given that the current Tasks RCU use cases wait for trampolines > to be evacuated, Tasks RCU could make the choice that cond_resched() > be a quiescent state, for example, by adjusting rcu_all_qs() and > .rcu_urgent_qs accordingly. > > But this seems less pressing given the chance that cond_resched() might > go away in favor of lazy preemption. Although cond_resched() is technically a "preemption point" and not truly a voluntary schedule, I would be happy to state that it's not allowed to be called from trampolines, or their callbacks. Now the question is, does BPF programs ever call cond_resched()? I don't think they do. [ Added Alexei ] -- Steve
