On Mon, Aug 29, 2016 at 12:40:32PM -0400, Chris Metcalf wrote:
On 8/29/2016 12:33 PM, Peter Zijlstra wrote:Naked use of TIF_NEED_RESCHED like this is busted. There is more state
On Tue, Aug 16, 2016 at 05:19:27PM -0400, Chris Metcalf wrote:Can you elaborate?
+ /*This is broken.. and it would be really good if you don't actually need
+ * 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);
to do this.
that needs to be poked to keep things consistent / working.