On Mon, Oct 18, 2021 at 11:50:46PM +0200, Frederic Weisbecker wrote: > On Mon, Oct 18, 2021 at 11:36:04AM -0700, Paul E. McKenney wrote: > > On Mon, Oct 18, 2021 at 07:42:42PM +0200, Frederic Weisbecker wrote: > > > I think you're right. The real issue is something I wanted to > > > fix next: RCU_SEGCBLIST_RCU_CORE isn't cleared when nocb is enabled on > > > boot so rcu_core() always run concurrently with nocb kthreads in TREE04, > > > without holding rcu_barrier mutex of course (I mean with the latest patchset). > > > > That would do it! > > > > > Ok forget this patch, I'm testing again with simply clearing > > > RCU_SEGCBLIST_RCU_CORE on boot. > > > > Sounds good, looking forward to it! > > So yes that was indeed the real issue. I've pushed an "rcu/rt-v3" branch > which is the same as your dev.2021.10.07a branch but the first patch > "rcu/nocb: Prepare state machine for a new step" has this added: > > diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h > index 3b470113ae38..2461fe8d0c23 100644 > --- a/kernel/rcu/tree_nocb.h > +++ b/kernel/rcu/tree_nocb.h > @@ -1171,8 +1171,8 @@ void __init rcu_init_nohz(void) > if (rcu_segcblist_empty(&rdp->cblist)) > rcu_segcblist_init(&rdp->cblist); > rcu_segcblist_offload(&rdp->cblist, true); > - rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB); > - rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_GP); > + rcu_segcblist_set_flags(&rdp->cblist, SEGCBLIST_KTHREAD_CB | SEGCBLIST_KTHREAD_GP); > + rcu_segcblist_clear_flags(&rdp->cblist, SEGCBLIST_RCU_CORE); > } > rcu_organize_nocb_kthreads(); > } > > > I still see the oom though, hopefully my series just makes an existing > problem more likely to happen. Yes, I have been seeing that without your patch, at least unless I bump up memory a bit. Looking forward to the new series! Thanx, Paul
