On Sat, Dec 30, 2017 at 10:40:41AM -0500, Theodore Ts'o wrote: > On Fri, Dec 29, 2017 at 10:16:24PM -0800, Matthew Wilcox wrote: > > > The problems come from wrong classification. Waiters either classfied > > > well or invalidated properly won't bitrot. > > > > I disagree here. As Ted says, it's the interactions between the > > subsystems that leads to problems. Everything's goig to work great > > until somebody does something in a way that's never been tried before. > > The question what is classified *well* mean? At the extreme, we could > put the locks for every single TCP connection into their own lockdep > class. But that would blow the limits in terms of the number of locks > out of the water super-quickly --- and it would destroy the ability > for lockdep to learn what the proper locking order should be. Yet > given Lockdep's current implementation, the only way to guarantee that > there won't be any interactions between subsystems that cause false > positives would be to categorizes locks for each TCP connection into > their own class. I'm not sure I agree with this part. What if we add a new TCP lock class for connections which are used for filesystems/network block devices/...? Yes, it'll be up to each user to set the lockdep classification correctly, but that's a relatively small number of places to add annotations, and I don't see why it wouldn't work.
