On Mon, Sep 11, 2023 at 4:16 AM Paul E. McKenney <paulmck@xxxxxxxxxx> wrote: [..] > > I am digging deeper to see why the rcu_preempt thread cannot be pushed out > > and then I'll also look at why is it being pushed out in the first place. > > > > At least I have a strong repro now running 5 instances of TREE03 in parallel > > for several hours. > > Very good! Then why not boot with rcutorture.onoff_interval=0 and see if > the problem still occurs? If yes, then there is definitely some reason > other than CPU hotplug that makes this happen. Hi Paul, So looks so far like onoff_interval=0 makes the issue disappear. So likely hotplug related. I am ok with doing the cpus_read_lock during boost testing and seeing if that fixes it. If it does, I can move on to the next thing in my backlog. What do you think? Or should I spend more time root-causing it? It is most like runaway RT threads combined with the CPU hotplug threads, making scheduling of the rcu_preempt thread not happen. But I can't say for sure without more/better tracing (Speaking of better tracing, I am adding core-dump support to rcutorture, but it is not there yet). thanks, - Joel
