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>

1 files changed, 2 insertions, 2 deletions

diff --git a/kernel/cgroup_pids.c b/kernel/cgroup_pids.c
index 45f0856a61fe..cdd8df4e991c 100644
--- a/kernel/cgroup_pids.c
+++ b/kernel/cgroup_pids.c
@@ -266,7 +266,7 @@ static void pids_fork(struct task_struct *task, void *priv)
 	css_put(old_css);
 }
 
-static void pids_exit(struct task_struct *task)
+static void pids_free(struct task_struct *task)
 {
 	struct pids_cgroup *pids = css_pids(task_css(task, pids_cgrp_id));
 
@@ -347,7 +347,7 @@ struct cgroup_subsys pids_cgrp_subsys = {
 	.can_fork	= pids_can_fork,
 	.cancel_fork	= pids_cancel_fork,
 	.fork		= pids_fork,
-	.exit		= pids_exit,
+	.free		= pids_free,
 	.legacy_cftypes	= pids_files,
 	.dfl_cftypes	= pids_files,
 };