On Tue, Nov 21, 2023 at 07:58:40AM -0800, Paul E. McKenney wrote: > Tasks Trace RCU allows general blocking in its readers, not just the > subject-to-priority-boosting blocking permitted within preemptible RCU > readers. Restrictions on the use of Tasks Trace RCU are in place to allow > getting away with this general blocking. Even systems generously endowed > with memory are not going to do well when the RCU grace period is blocked > on I/O, especially if that I/O is across a network to a slow file server. > > Which means a separate RCU instance is needed. Which is Tasks Trace RCU. Separate instance not a problem, nor really the question. What is the basic mechanism of task-tracing? Is it really the existing tasks-rcu extended with read-side critical sections and call_rcu ? If so, then why not have it be tasks-rcu? Or is it a variant of the preemptible/SRCU class of RCUs that are counter-array based? I suspect not. So once again, what exactly is tasks-tracing ?
