On 06/26/2015 06:08 PM, Thomas Gleixner wrote: > On Fri, 26 Jun 2015, Preeti U Murthy wrote: >> On 06/26/2015 01:17 PM, Thomas Gleixner wrote: >>> if (state == TICK_BROADCAST_ENTER) { >>> + /* >>> + * If the current CPU owns the hrtimer broadcast >>> + * mechanism, it cannot go deep idle and we do not add >>> + * the CPU to the broadcast mask. We don't have to go >>> + * through the EXIT path as the local timer is not >>> + * shutdown. >>> + */ >>> + ret = broadcast_needs_cpu(bc, cpu); >>> + >>> + /* >>> + * If the hrtimer broadcast check tells us that the >>> + * cpu cannot go deep idle, or if the broadcast device >>> + * is in periodic mode, we just return. >>> + */ >>> + if (ret || tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) >>> + goto out; >> >> The check on PERIODIC mode is good, but I don't see the point of moving >> broadcast_needs_cpu() up above. broadcast_shutdown_local() calls >> broadcast_needs_cpu() internally. >> >> Besides, by jumping to 'out', we will miss programming the broadcast >> hrtimer in tick_broadcast_set_event() below, if the cpu happen to be the >> broadcast cpu(which is why it was not allowed to go to deep idle). > > Hmm. Need to think a bit more about this convoluted maze ...
I think you cover all cases just by having that check on periodic mode. This covers the nohz_full=n,highres=n, TICK_ONESHOT=y and GENERIC_CLOCKEVENTS_BROADCAST=y. broadcast_needs_cpu() should remain where it was though. And of course, the additional patch on tick_broadcast_device.evtdev == NULL in BROADCAST_ON. Regards Preeti U Murthy > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/