On Mon, Nov 11, 2013 at 05:07:22PM +0100, Stephane Eranian wrote: > On Mon, Nov 11, 2013 at 4:59 PM, Peter Zijlstra <[email protected]> wrote: > > On Fri, Nov 08, 2013 at 08:46:02PM +0100, Stephane Eranian wrote: > > > > > >> +static DEFINE_SPINLOCK(rapl_hotplug_lock); > > > > What is this thing protecting? > > > > Like last time it appears to be used only from hotplug notifier > > callbacks and those are already fully serialized. > > > I thought you or somebody else had said, that hotplug in now parallel.
There's a little something about hotplug here I think: http://marc.info/?l=linux-kernel&m=138118235612441 But I'm not entirely sure that's the origin of this lock. Andi seems worried about the IPI vs hotplug/migrate. I'm not entrely sure the lock as proposed actually fixes that. The 'easy' way would be to put a synchronize_sched() right after the migrate code, that forces all CPUs to have scheduled once and thus also ensures all pending/running interrupts are serviced. But I don't think that's strictly required as I seem to recall hotplug actually already does something like this -- it pretty much has to. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
