> pidlist is hanlding is quite elaborate. Because the pidlist files - > "tasks" and "cgroup.pids" - guarantee that the result is sorted and a > task can be associated with different pids, with no inherent order > among them, depending on namespaces, it is impossible to give a > certain order to tasks of a cgroup and then just iterate through them. > > Instead, we end up creating tables of the relevant ids and then sort > them before serving them out for reads. As those tables can be huge, > we also implement logic to share those tables if the id type and > namespace match, which in turn involves reference counting those > tables and synchronizing accesses to them. > > What could have been a simple iteration through the member tasks > became this unnecessary hunk of complexity because it, for some > reason, wanted to guarantee sorted output, which is extremely unusual > for this type of interface. > > The refcnting is done from open() and release() callbacks, which > kernfs doesn't expose. This patchset updates pidlist handling so that > pidlists are managed from seq_file operations proper. As the duration > between the paired start and stop denotes a single read invocation and > we don't want to reload pidlist for each instance of consecutive read > calls, pidlist is released with time delay. This also bounds the > stale the output of read calls can be. This makes refcnting > unnecessary - locking is simplified and refcnting is dropped. > > In the long term, we want to do away with pidlist and make this a > simple iteration over member tasks. The last patch scrambles the sort > order of "cgroup.pids" if sane_behavior, so that the sorted > expectation is broken in the new interface and we can eventually drop > pidlist logic. > > This patchset contains the following nine patches. > > 0001-cgroup-don-t-skip-seq_open-on-write-only-opens-on-pi.patch > 0002-cgroup-remove-cftype-release.patch > 0003-cgroup-implement-delayed-destruction-for-cgroup_pidl.patch > 0004-cgroup-introduce-struct-cgroup_pidlist_open_file.patch > 0005-cgroup-refactor-cgroup_pidlist_find.patch > 0006-cgroup-remove-cgroup_pidlist-rwsem.patch > 0007-cgroup-load-and-release-pidlists-from-seq_file-start.patch > 0008-cgroup-remove-cgroup_pidlist-use_count.patch > 0009-cgroup-don-t-guarantee-cgroup.procs-is-sorted-if-san.patch > Acked-by: Li Zefan <lizefan@xxxxxxxxxx> _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
