On Thu, Dec 29, 2022 at 05:10:28PM +0000, Lorenzo Stoakes wrote: > On Thu, Dec 29, 2022 at 04:51:37PM +0000, Matthew Wilcox wrote: > > The mmap_lock is taken for many, many things. [snip] > > I am currently describing the use of this lock (for 6.0) in the book and it is > striking just how broadly it's used. I'm diagramming it out for 'core' users, > i.e. non-driver and non-some other things, but even constraining that leaves a > HUGE number of users. I fear this would be overwhelming. I don't think anybody would disagree that the mmap_lock needs to be split up like the BKL was, but we didn't do that by diagramming it out. Instead, we introduced new smaller locks that protected much better-defined things until eventually we were able to kill the BKL entirely. That's what I'm trying to do here -- there is one well-defined thing that the maple tree lock will protect, and that's the structure of the maple tree. It doesn't protect the data pointed to by the pointers stored in the tree, just the maple tree itself. > I've also documented the 'unexpected' uses of the > page_table_lock, which seems to have been significantly improved over time but > still a few cases remain! Now, I think this is useful. There's probably few enough abuses of the PTL that my brain can wrap itself around which ones are legitimate and then deal with the inappropriate ones. > Am happy to give you (+ anybody else on MAINTAINERS list) an early copy of the > relevant bit (once I've finished the diagrams anyway) if that'd be helpful! I'm definitely interested in the PTL. Thank you for the offer! > Now if you guys could stop obsoleting my work that'd be great ;) Never! How else will you get interest in the Second Edition Covering Linux 7.0? ;-)
