On 10/01, Peter Zijlstra wrote: > > On Tue, Oct 01, 2013 at 10:41:15PM +0530, Srivatsa S. Bhat wrote: > > However, as Oleg said, its definitely worth considering whether this proposed > > change in semantics is going to hurt us in the future. CPU_POST_DEAD has certainly > > proved to be very useful in certain challenging situations (commit 1aee40ac9c > > explains one such example), so IMHO we should be very careful not to undermine > > its utility. > > Urgh.. crazy things. I've always understood POST_DEAD to mean 'will be > called at some time after the unplug' with no further guarantees. And my > patch preserves that. I tend to agree with Srivatsa... Without a strong reason it would be better to preserve the current logic: "some time after" should not be after the next CPU_DOWN/UP*. But I won't argue too much. But note that you do not strictly need this change. Just kill cpuhp_waitcount, then we can change cpu_hotplug_begin/end to use xxx_enter/exit we discuss in another thread, this should likely "join" all synchronize_sched's. Or split cpu_hotplug_begin() into 2 helpers which handle FAST -> SLOW and SLOW -> BLOCK transitions, then move the first "FAST -> SLOW" handler outside of for_each_online_cpu(). Oleg. -- 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>