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. Thanks.
