* H. Peter Anvin <hpa@xxxxxxxxx> wrote: > On 12/19/2013 09:07 AM, Ingo Molnar wrote: > > > > Likewise, having a barrier before the MONITOR looks sensible as > > well. Having it _after_ monitor looks weird and is probably wrong. > > [It might have been the effects of someone seeing the spurious > > wakeup problems with realizing the true source, or so.] > > Does anyone know the history of this barrier after the monitor? I > know Len is looking for a minimal patchset that can go into -stable, > and it seems prudent to not preturb the code more than necessary, > but going forward it would be nice to know... For the minimal fix I don't think we should change it - but for v3.14 it looks like a speedup for the from-idle codepath, which is performance sensitive. ( It would also be nice to know whether MONITOR loads that cacheline into the CPUs cache, and in what state it loads it. ) Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html