diff options
| -rw-r--r-- | Documentation/cgroups/cgroups.txt | 14 | ||||
| -rw-r--r-- | include/linux/cgroup.h | 1 | ||||
| -rw-r--r-- | kernel/cgroup.c | 16 |
3 files changed, 27 insertions, 4 deletions
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt index 821de56d1580..10c949b293e4 100644 --- a/Documentation/cgroups/cgroups.txt +++ b/Documentation/cgroups/cgroups.txt @@ -599,6 +599,20 @@ fork. If this method returns 0 (success) then this should remain valid while the caller holds cgroup_mutex and it is ensured that either attach() or cancel_attach() will be called in future. +void css_reset(struct cgroup_subsys_state *css) +(cgroup_mutex held by caller) + +An optional operation which should restore @css's configuration to the +initial state. This is currently only used on the unified hierarchy +when a subsystem is disabled on a cgroup through +"cgroup.subtree_control" but should remain enabled because other +subsystems depend on it. cgroup core makes such a css invisible by +removing the associated interface files and invokes this callback so +that the hidden subsystem can return to the initial neutral state. +This prevents unexpected resource control from a hidden css and +ensures that the configuration is in the initial state when it is made +visible again later. + void cancel_attach(struct cgroup *cgrp, struct cgroup_taskset *tset) (cgroup_mutex held by caller) diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h index 5287f931680a..db99e3b923b1 100644 --- a/include/linux/cgroup.h +++ b/include/linux/cgroup.h @@ -642,6 +642,7 @@ struct cgroup_subsys { int (*css_online)(struct cgroup_subsys_state *css); void (*css_offline)(struct cgroup_subsys_state *css); void (*css_free)(struct cgroup_subsys_state *css); + void (*css_reset)(struct cgroup_subsys_state *css); int (*can_attach)(struct cgroup_subsys_state *css, struct cgroup_taskset *tset); diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 331fa296c7e0..3a6b77d7ba4a 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -2740,17 +2740,25 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of, /* * All tasks are migrated out of disabled csses. Kill or hide * them. A css is hidden when the userland requests it to be - * disabled while other subsystems are still depending on it. + * disabled while other subsystems are still depending on it. The + * css must not actively control resources and be in the vanilla + * state if it's made visible again later. Controllers which may + * be depended upon should provide ->css_reset() for this purpose. */ for_each_subsys(ss, ssid) { if (!(disable & (1 << ssid))) continue; cgroup_for_each_live_child(child, cgrp) { - if (css_disable & (1 << ssid)) - kill_css(cgroup_css(child, ss)); - else + struct cgroup_subsys_state *css = cgroup_css(child, ss); + + if (css_disable & (1 << ssid)) { + kill_css(css); + } else { cgroup_clear_dir(child, 1 << ssid); + if (ss->css_reset) + ss->css_reset(css); + } } } |