On Thursday 08 November 2007 01:20, Matt Mackall wrote: > On Wed, Nov 07, 2007 at 12:30:45PM -0800, Andrew Morton wrote: > > Ow. Yes, from my reading delay_tsc() can return early (or after > > heat-death-of-the-universe) if the TSCs are offset and if preemption > > migrates the calling task between CPUs. > > > > I suppose a lameo fix would be to disable preemption in delay_tsc(). > > preempt_disable is lousy documentation here. This and other cases > (lots of per_cpu users, IIRC) actually want a migrate_disable() which > is a proper subset. We can simply implement migrate_disable() as > preempt_disable() for now and come back later and implement a proper > migrate_disable() that still allows preemption (and thus avoids the > latency).
We could actually do this right now. migrate_disable() can be just changing the cpu affinity of the current thread to current cpu and then restoring it afterwards. That should even work from interrupt context. get_cpu() etc. could be changed to use this then too. -Andi - 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/
