On Mon, 2018-07-09 at 13:42 -0700, Paul E. McKenney wrote: > On Mon, Jul 09, 2018 at 09:35:38PM +0100, David Woodhouse wrote: > > > > > > On Mon, 2018-07-09 at 13:34 -0700, Paul E. McKenney wrote: > > > > > > So here are the possible code paths when .rcu_urgent_qs is set to true: > > > > > > 1. A context switch will record the quiescent state and clear > > > .rcu_urgent_qs. (The failure to do the clearing in current -rcu > > > for PREEMPT builds is a performance bug that I need to fix.) > > > > What if there's nothing else runnable and there is no actual context > > switch? > > The scheduler invokes rcu_note_context_switch() before looking to see > if there really will or won't be a context switch. > > I am sure that Peter will correct me if I am confused on this point. ;-)
Ah, OK. Yes, that looks correct. Thanks. I'll give your patch a spin tomorrow, unless Marius beats me to it.
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