On Thu, 10 Oct 2013 13:13:05 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> > > > > > Why prevent all CPUs from running when we want to remove > > > > one? > > > > > > So get_online_cpus() goes away. Nothing is more scalable than nothing! > > > > Very much agreed; now stop_machine() wouldn't actually work for hotplug > > because it will instantly preempt everybody, including someone who might > > be in the middle of using per-cpu state of the cpu we're about to > > remove. > > Well, stop machine doesn't instantly preempt everybody. Only those that > don't have preemption disabled. Using per_cpu without preemption > disabled can be dangerous. Yes, I'd have thought that the cases where a CPU is fiddling with another CPU's percpu data with preemption enabled would be rather rare. I can't actually think of any off the top. Are there examples we can look at? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
