On Fri, Jan 15, 2016 at 03:14:10PM -0800, Paul E. McKenney wrote: > And if I make the scheduling-clock interrupt send extra wakeups to the RCU > grace-period kthread when needed, things work even with CPU hotplug going. > > The "when needed" means any time that the RCU grace-period kthread has > been sleeping three times as long as the timeout interval. If the first > wakeup does nothing, it does another wakeup once per second. > > So it looks like this change makes an existing problem much worse, as > opposed to introducing a new problem.
I have a vague idea about a possible race window. Have you been observing this on PPC or x86? The reason I'm asking is that PPC (obviously) allows for more races :-)
