cgroups: ignore unused controllers

Someone might have created a name=<controller> controller after the
container has started and so the container doesn't make use of this
controller.

Link: https://github.com/lxc/lxd/issues/8577
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>

diff --git a/src/lxc/cgroups/cgfsng.c b/src/lxc/cgroups/cgfsng.c
index 46ed69714f6d2e31afc074763afc047292a6a6c3..f66790a4df2e61661ef87cce4c3c37902378c27b 100644 (file)
--- a/src/lxc/cgroups/cgfsng.c
+++ b/src/lxc/cgroups/cgfsng.c
@@ -2363,9 +2363,17 @@ __cgfsng_ops static bool cgfsng_attach(struct cgroup_ops *ops,
                }
 
                path = lxc_cmd_get_cgroup_path(name, lxcpath, h->controllers[0]);
-               /* not running */
-               if (!path)
-                       return false;
+               if (!path) {
+                       /*
+                        * Someone might have created a name=<controller>
+                        * controller after the container has started and so
+                        * the container doesn't make use of this controller.
+                        *
+                        * Link: https://github.com/lxc/lxd/issues/8577
+                        */
+                       TRACE("Skipping unused %s controller", maybe_empty(h->controllers[0]));
+                       continue;
+               }
 
                fullpath = build_full_cgpath_from_monitorpath(h, path, "cgroup.procs");
                ret = lxc_write_to_file(fullpath, pidstr, len, false, 0666);