On Wed, 2018-03-28 at 10:09 +0100, Will Deacon wrote: > On Wed, Mar 28, 2018 at 09:00:01AM +0000, David Laight wrote: > > From: Will Deacon > > > Sent: 28 March 2018 09:54 > > > > ... > > > > > I don't think so. My reading of memory-barriers.txt says that writeX might > > > > > expand to outX, and outX is not ordered with respect to other types of > > > > > memory. > > > > > > > > Ugh ? > > > > > > > > My understanding of HW at least is the exact opposite. outX is *more* > > > > ordered if anything, than any other accessors. IO space is completely > > > > synchronous, non posted and ordered afaik. > > > > > > I'm just going by memory-barriers.txt: > > > > > > > > > (*) inX(), outX(): > > > > > > [...] > > > > > > They are guaranteed to be fully ordered with respect to each other. > > > > > > They are not guaranteed to be fully ordered with respect to other types of > > > memory and I/O operation. > > > > A long time ago there was a document from Intel that said that inb/outb weren't > > necessarily synchronised wrt memory accesses. > > (Might be P-pro era). > > However no processors actually behaved that way and more recent docs > > say that inb/outb are fully ordered. > > Thank you, David! I'll write another patch fixing this up and hopefully > we'll soon have one making writeX/readX much clearer. Thanks for doing the grunt work Will ! :-) Cheers, Ben. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
