On Mon, Mar 16, 2020 at 3:47 PM Joel Fernandes <joel@xxxxxxxxxxxxxxxxx> wrote: > > On Thu, Mar 12, 2020 at 11:16:55AM -0700, paulmck@xxxxxxxxxx wrote: > > From: "Paul E. McKenney" <paulmck@xxxxxxxxxx> > > > > This commit adds a "rude" variant of RCU-tasks that has as quiescent > > states schedule(), cond_resched_tasks_rcu_qs(), userspace execution, > > and (in theory, anyway) cond_resched(). Updates make use of IPIs and > > force an IPI and a context switch on each online CPU. This variant > > is useful in some situations in tracing. > > Would it be possible to better clarify that the "rude version" works only > from preempt-disabled regions? Is that also true for the "non-rude" version? > > Also it would be good to clarify better in cover letter, how these new > flavors relate to the existing Tasks-RCU implementation. > > In the existing one, a quiescent state is a task updating its context switch > counters such that it went to sleep at least once, implying there is no > chance it is on an about to be destroyed trampoline. > > However, here we are trying to determine if a task state is no longer on an > RQ (which I gleaned from the first patch). Sounds very similar, would the > context switch counters not help in that determination as well? If it is Ok, > it would be good to describe in cover letter about what is exactly is a > quiescent state and what exactly is a reader section in the cover letter, for > both non-rude and rude version. Thanks! Just curious, why is the "rude" version better than SRCU? Seems the schedule_on_each_cpu() would be much slower than SRCU especially if there are 1000s of CPUs involved. Is there any reason that is a better alternative? thanks, - Joel
