On Wed, Feb 18, 2009 at 08:09:21AM -0800, Linus Torvalds wrote: > > > On Wed, 18 Feb 2009, Nick Piggin wrote: > > > > I agree with you both that we *should* make arch interrupt code > > do the ordering, but given the subtle lockups on some architectures > > in this new code, I didn't want to make it significantly weaker... > > > > Though perhaps it appears that I have, if I have removed an smp_mb > > that x86 was relying on to emit an mfence to serialise the apic. > > The thing is, if the architecture doesn't order IPI wrt cache coherency, > then the "smp_mb()" doesn't really do so _either_. Oh yes agreed three, which is why I'm saying it is just a hack and should be removed at some point. > It might hide some architecture-specific implementation issue, of course, > so random amounts of "smp_mb()"s sprinkled around might well make some > architecture "work", but it's in no way guaranteed. A smp_mb() does not > guarantee that some separate IPI network is ordered - that may well take > some random machine-specific IO cycle. Yes, but I didn't want to pull out that smp_mb() at least until arch maintainers can ack it. Just because there might indeed be some random issue hidden by it. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
