On Fri, 17 Jun 2011, Linus Torvalds wrote: > On Fri, Jun 17, 2011 at 11:32 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote: > > > > something like so I guess, completely untested etc.. > > Having gone over it a bit more, I actually think I prefer to just > special-case the allocation instead. > > We already have to drop the anon_vma lock for the "out of memory" > case, and a slight re-organization of clone_anon_vma() makes it easy > to just first try a NOIO allocation with the lock still held, and then > if that fails do the "drop lock, retry, and hard-fail" case. > > IOW, something like the attached (on top of the patches already posted > except for your memory reclaim thing) > > Hugh, does this fix the lockdep issue? Yes, that fixed the lockdep issue, and ran nicely under load for an hour. I agree that it's better to do this GFP_NOWAIT and fallback, than trylock the anon_vma. And I'm happy that you've still got that WARN_ON_ONCE(root) in: I do not have a fluid mental model of the anon_vma_chains, get lost there; and though it's obvious that we must have the same anon_vma->root going down the same_anon_vma list, I could not put my finger on a killer demonstration for why the same has to be true of the same_vma list. But I've not seen your WARN_ON_ONCE fire, and it's hard to imagine how there could be more than one root in the whole bundle of lists. Hugh -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>