Hi, I'm trying to understand why stop_machine() is necessary for cpu_down() operation. I see that multi_cpu_stop() on every online cpu (which hogs the cpu and then triggers state changes state) and then, take_cpu_down is invoked on the outgoing cpu. This happens by every cpu decrementing the msdata->thread_ack and last one trigger a state change. I'm trying to understand why is this necessary. Is to wait for RCU grace period(s)? If yes, what variable/struct is being protected and how does stop_machine() help there? I see there was a patch (https://lwn.net/Articles/538819/) but had some issues with idle_loop. Is there an alternative where the stop_machine would not be necessary? Or more specifically, is there a reason why every CPU would need to stop? Any help would be appreciated. Thanks, Hardik -- To unsubscribe from this list: send the line "unsubscribe linux-hotplug" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
