Thomas, 2013/2/23 Thomas Gleixner <t...@linutronix.de>: > On Fri, 22 Feb 2013, Lorenzo Pieralisi wrote: >> On Fri, Feb 22, 2013 at 03:03:02PM +0000, Thomas Gleixner wrote: >> > On Fri, 22 Feb 2013, Lorenzo Pieralisi wrote: >> > > On Fri, Feb 22, 2013 at 12:07:30PM +0000, Thomas Gleixner wrote: >> > > > Now we could make use of that and avoid going deep idle just to come >> > > > back right away via the IPI. Unfortunately the notification thingy has >> > > > no return value, but we can fix that. >> > > > >> > > > To confirm that theory, could you please try the hack below and add >> > > > some instrumentation (trace_printk)? >> > > >> > > Applied, and it looks like that's exactly why the warning triggers, at >> > > least >> > > on the platform I am testing on which is a dual-cluster ARM testchip. >> > > >> > > There is a still time window though where the CPU (the IPI target) can >> > > get >> > > back to idle (tick_broadcast_pending still not set) before the CPU >> > > target of >> > > the broadcast has a chance to run tick_handle_oneshot_broadcast (and set >> > > tick_broadcast_pending), or am I missing something ? >> > >> > Well, the tick_broadcast_pending bit is uninteresting if the >> > force_broadcast bit is set. Because if that bit is set we know for >> > sure, that we got woken with the cpu which gets the broadcast timer >> > and raced back to idle before the broadcast handler managed to >> > send the IPI. >> >> Gah, my bad sorry, I mixed things up. I thought >> >> tick_check_broadcast_pending() >> >> was checking against the tick_broadcast_pending mask not >> >> tick_force_broadcast_mask > > Yep, that's a misnomer. I just wanted to make sure that my theory is > correct. I need to think about the real solution some more.
I have applied your patch and tested, there is NO warning at all then. I think your theory is correct. > > We have two alternatives: > > 1) Make the clockevents_notify function have a return value. > > 2) Add something like the hack I gave you with a proper name. > > The latter has the beauty, that we just need to modify the platform > independent idle code instead of going down to every callsite of the > clockevents_notify thing. I prefer the solution 2). > > Thanks, > > tglx -- 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/
