> > Yeah, they keep threatening to use this instead, but I'm not sure > > how easy it would be. Also they may have more devices/drivers to > > worry about than sn2, so maybe changing over would mean too much > > driver debugging (well auditing really since it's not that hard to > > know where to put them). Irix actually had an io_unlock() routine > > that did this implicitly, but iirc that was shot down for Linux... > > Why was it shot down? Seems like a pretty good idea to me ;)
Well, like Linus said, it had some significant downsides (though I think Irix had fewer lock types, so the multiplicative effect wasn't so bad there). > I'm clueless when it comes to drivers, but I see a lot of mmiowb() > that are not paired with spin_unlock. How are these obvious? (ie. > what is the pattern?) It looks like some might be lockless FIFOs (or > maybe I'm just not aware of where the locks are). Can you just > quickly illustrate the problem being solved? Wow, it certainly has proliferated since it was added to the tree. :) I didn't audit all the uses, but it seems like many of them get it right, i.e. mmiowb() before spin_unlock() where PIO has been done. I'd have to look carefully to see whether lockless usages are correct, it's likely they're not. Jesse _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
