On Fri, 19 May 2017 10:04:21 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> On Fri, 19 May 2017 06:35:50 -0700 > "Paul E. McKenney" <paul...@linux.vnet.ibm.com> wrote: > > > Simpler would be better! > > > > However, is it really guaranteed that one SCHED_IDLE thread cannot > > preempt another? If not, then the trampoline-freeing SCHED_IDLE thread > > might preempt some other SCHED_IDLE thread in the middle of a trampoline. > > I am not seeing anything that prevents such preemption, but it is rather > > early local time, so I could easily be missing something. > > > > However, if SCHED_IDLE threads cannot preempt other threads, even other > > SCHED_IDLE threads, then your approach sounds quite promising to me. > > > > Steve, Peter, thoughts? > > SCHED_IDLE is the swapper task. There's one on each CPU, and they don't > migrate. And they only get called when there's no other task running. Peter just "schooled" me on IRC. I stand corrected (and he may respond to this email too). I guess any task can become SCHED_IDLE. But that just makes this an even less likely option for synchronize_rcu_tasks(). -- Steve
