On Wed, 8 Feb 2017, Christoph Lameter wrote: > On Wed, 8 Feb 2017, Thomas Gleixner wrote: > > > There is a world outside yours. Hotplug is actually used frequently for > > power purposes in some scenarios. > > The usual case does not inolve hotplug. We do not care about your definition of "usual". The kernel serves _ALL_ use cases. > > It will improve nothing. The stop machine context is extremly limited and > > you cannot do complex things there at all. Not to talk about the inability > > of taking a simple mutex which would immediately deadlock the machine. > > You do not need to do complex things. Basically flipping some cpu mask > bits will do it. stop machine ensures that code is not > executing on the processors when the bits are flipped. That will ensure > that there is no need to do any get_online_cpu() nastiness in critical VM > paths since we are guaranteed not to be executing them. And how does that solve the problem at hand? Not at all: CPU 0 CPU 1 for_each_online_cpu(cpu) ==> cpu = 1 stop_machine() set_cpu_online(1, false) queue_work(cpu1) Thanks, tglx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
