On 09/17/2012 09:21 PM, Tejun Heo wrote: > Hello, Glauber. > > On Mon, Sep 17, 2012 at 12:50:47PM +0400, Glauber Costa wrote: >>> Can you be a bit more specific? >> >> What I mean is that if some operation needs to operate locked, they will >> have to lock. Whether or not the locking is called from cgroup core or >> not. If the lock is not available outside, people will end up calling a >> core function that locks. > > I was asking whether you have certain specific operations on mind. > >>>> And the problem is that people need to lock. cgroup_lock is needed >>>> because the data you are accessing is protected by it. The way I see it, >>>> it is incredible how we were able to revive the BKL in the form of >>>> cgroup_lock after we finally manage to successfully get rid of it! >>> >>> I wouldn't go as far as comparing it to BKL. >> >> Of course not, since it is not system-wide. But I think the comparison >> still holds in spirit... > > Subsystem-wide locks covering non-hot paths aren't evil things. We > have a lot of them and they work fine. BKL was a completely different > beast initially with implicit locking on kernel entry and unlocking on > sleeping and then got morphed into some chimera inbetween afterwards. > > Simple locking is a good thing. If finer-grained locking is > necessary, we sure do that but please stop throwing over-generalized > half-arguments at it. It doesn't help anything. > >> you seem to hear "comount", and think of unified vision, and that is the >> reason for this discussion to still be going on. Mounting is all about >> the root. And if you comount, hierarchies have the same root. >> >> In your example, the different controllers are comounted. They have not >> the same view, but the possible views are restricted to be a subset of >> the underlying tree - because they are mounted in the same place, forced >> or not. > > Heh, I can't really tell whether you understand it or not. Here and > in the previous thread too. You seem to understand that there are > different views upto this point. > >> In a situation like this, it makes all the sense in the world to use the >> css_id as a primary identifier, because it will be guaranteed to be the > > And then you say something like this (or that this would remove > walking different hierarchies in the previous thread - yes, to a > certain point but not completely). css_id is a per-css attribute. > How can that be the "primariy" identifier when there can be multiple > views? For each userland-visible cgroup, there must be a css_set > which points to the css's belonging to it, which may not be at the > same level - multiple nodes in the userland visible tree may point to > the same css. > > If you mean that css_id would be the primary identifier for that > specific controller's css, why even say that? That's true now and > won't ever change. > >> same. What makes the tree overly flexible, is that you can have multiple >> roots, starting in multiple places, with arbitrary topologies downwards. > > And now you seem to be on the same page again. But then again, you're > asserting that incorporating forced co-mounts *now* is a gradual step > towards the goal, which is utterly bonkers. I don't know. I just > can't understand what you're thinking at all. > > Thanks. > I will just stop, because i am not trying to convince you to do anything different than you are proposing now. I am just trying to convince you what I have been saying has the exact same effects of this. So let us focus our energies in the actual work _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
