On Mon, Aug 29, 2016 at 12:40:32PM -0400, Chris Metcalf wrote: > On 8/29/2016 12:33 PM, Peter Zijlstra wrote: > >On Tue, Aug 16, 2016 at 05:19:27PM -0400, Chris Metcalf wrote: > >>+ /* > >>+ * Request rescheduling unless we are in full dynticks mode. > >>+ * We would eventually get pre-empted without this, and if > >>+ * there's another task waiting, it would run; but by > >>+ * explicitly requesting the reschedule, we may reduce the > >>+ * latency. We could directly call schedule() here as well, > >>+ * but since our caller is the standard place where schedule() > >>+ * is called, we defer to the caller. > >>+ * > >>+ * A more substantive approach here would be to use a struct > >>+ * completion here explicitly, and complete it when we shut > >>+ * down dynticks, but since we presumably have nothing better > >>+ * to do on this core anyway, just spinning seems plausible. > >>+ */ > >>+ if (!tick_nohz_tick_stopped()) > >>+ set_tsk_need_resched(current); > >This is broken.. and it would be really good if you don't actually need > >to do this. > > Can you elaborate? Naked use of TIF_NEED_RESCHED like this is busted. There is more state that needs to be poked to keep things consistent / working. -- 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>