On Wed, 2012-09-12 at 14:41 +0200, Peter Zijlstra wrote: > We could of course mandate that all remote wakeups to special nohz cpus > get queued. That would just leave us with RCU and it would simply not > send resched IPIs to extended quiescent CPUs anyway, right? > > So at that point all return to user schedule() calls have nr_running > 1 > and the tick is running and RCU is not in extended quiescent state. > Since either we had nr_running > 1 and pre and post state are the same, > or we had nr_running == 1 and we just got a fresh wakeup pushing it to > 2, the wakeup will have executed on our cpu and have re-started the tick > and kicked RCU into active gear again. > > We cannot hit return to user schedule() with nr_running == 0, simply > because in that case there's no userspace to return to, only the idle > thread and that's very much not userspace :-) > > Hmm ?
Crap.. this will screw over -rt, since the wakeups batch the IPI can take forever so we had to disable this. Bugger it.. I so detest this patch. -- 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/
