On Tue, 2020-07-14 at 15:03 +1000, Aleksa Sarai wrote: > On 2020-07-13, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote: > > Matt Bennett <Matt.Bennett@xxxxxxxxxxxxxxxxxxx> writes: > > > > > On Thu, 2020-07-02 at 21:10 +0200, Christian Brauner wrote: > > > > On Thu, Jul 02, 2020 at 08:17:38AM -0500, Eric W. Biederman wrote: > > > > > Matt Bennett <matt.bennett@xxxxxxxxxxxxxxxxxxx> writes: > > > > > > > > > > > Previously the connector functionality could only be used by processes running in the > > > > > > default network namespace. This meant that any process that uses the connector functionality > > > > > > could not operate correctly when run inside a container. This is a draft patch series that > > > > > > attempts to now allow this functionality outside of the default network namespace. > > > > > > > > > > > > I see this has been discussed previously [1], but am not sure how my changes relate to all > > > > > > of the topics discussed there and/or if there are any unintended side effects from my draft > > > > > > changes. > > > > > > > > > > Is there a piece of software that uses connector that you want to get > > > > > working in containers? > > > > > > We have an IPC system [1] where processes can register their socket > > > details (unix, tcp, tipc, ...) to a 'monitor' process. Processes can > > > then get notified when other processes they are interested in > > > start/stop their servers and use the registered details to connect to > > > them. Everything works unless a process crashes, in which case the > > > monitoring process never removes their details. Therefore the > > > monitoring process uses the connector functionality with > > > PROC_EVENT_EXIT to detect when a process crashes and removes the > > > details if it is a previously registered PID. > > > > > > This was working for us until we tried to run our system in a container. > > > > > > > > > > > > > I am curious what the motivation is because up until now there has been > > > > > nothing very interesting using this functionality. So it hasn't been > > > > > worth anyone's time to make the necessary changes to the code. > > > > > > > > Imho, we should just state once and for all that the proc connector will > > > > not be namespaced. This is such a corner-case thing and has been > > > > non-namespaced for such a long time without consistent push for it to be > > > > namespaced combined with the fact that this needs quite some code to > > > > make it work correctly that I fear we end up buying more bugs than we're > > > > selling features. And realistically, you and I will end up maintaining > > > > this and I feel this is not worth the time(?). Maybe I'm being too > > > > pessimistic though. > > > > > > > > > > Fair enough. I can certainly look for another way to detect process > > > crashes. Interestingly I found a patch set [2] on the mailing list > > > that attempts to solve the problem I wish to solve, but it doesn't > > > look like the patches were ever developed further. From reading the > > > discussion thread on that patch set it appears that I should be doing > > > some form of polling on the /proc files. > > > > Recently Christian Brauner implemented pidfd complete with a poll > > operation that reports when a process terminates. > > > > If you are willing to change your userspace code switching to pidfd > > should be all that you need. > > While this does solve the problem of getting exit notifications in > general, you cannot get the exit code. But if they don't care about that > then we can solve that problem another time. :D > >From first glance using pidfd will do exactly what we need. Not being able to get the exit code will not be an issue. In fact I think it will be an improvement over the connector as the listener will now only be waiting for the PIDs we actually care about - rather than getting woken up on every single process exit and having to check if it cares about the PID. Many thanks Eric and others, Matt _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
