On 2021-02-16 10:36:09 [-0800], Paul E. McKenney wrote: > Hello, Sebastian, Hi Paul, > I punted on this for the moment by making RCU priority boosting testing > depend on CONFIG_PREEMPT_RT, but longer term I am wondering if RCU's > various timed delays and timeouts should use hrtimers rather than normal > timers in kernels built with CONFIG_RCU_BOOST. As it is, RCU priority > boosting can be defeated if any of the RCU grace-period kthread's timeouts > are serviced by the non-realtime ksoftirqd. I though boosting is accomplished by acquiring a rt_mutex in a rcu_read() section. Do you have some code to point me to, to see how a timer is involved here? Or is it the timer saying that *now* boosting is needed. If your hrtimer is a "normal" hrtimer then it will be served by ksoftirqd, too. You would additionally need one of the HRTIMER_MODE_*_HARD to make it work. > This might require things like swait_event_idle_hrtimeout_exclusive(), > either as primitives or just open coded. > > Thoughts? > > Thanx, Paul Sebastian
