cgroup: add cgroup_subsys->free() method and use it to fix pids controller
pids controller is completely broken in that it uncharges when a task
exits allowing zombies to escape resource control. With the recent
updates, cgroup core now maintains cgroup association till task free
and pids controller can be fixed by uncharging on free instead of
exit.
This patch adds cgroup_subsys->free() method and update pids
controller to use it instead of ->exit() for uncharging.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Aleksa Sarai <cyphar@cyphar.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 9186584..8673843 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -206,6 +206,7 @@
*/
static unsigned long have_fork_callback __read_mostly;
static unsigned long have_exit_callback __read_mostly;
+static unsigned long have_free_callback __read_mostly;
/* Ditto for the can_fork callback. */
static unsigned long have_canfork_callback __read_mostly;
@@ -5180,6 +5181,7 @@
have_fork_callback |= (bool)ss->fork << ss->id;
have_exit_callback |= (bool)ss->exit << ss->id;
+ have_free_callback |= (bool)ss->free << ss->id;
have_canfork_callback |= (bool)ss->can_fork << ss->id;
/* At system boot, before all subsystems have been
@@ -5637,6 +5639,11 @@
void cgroup_free(struct task_struct *task)
{
struct css_set *cset = task_css_set(task);
+ struct cgroup_subsys *ss;
+ int ssid;
+
+ for_each_subsys_which(ss, ssid, &have_free_callback)
+ ss->free(task);
put_css_set(cset);
}