The pids.events file should honor the hierarchy, so make the events
propagate from their origin up to the root on the unified hierarchy. The
legacy behavior remains non-hierarchical.
Signed-off-by: Michal Koutný <mkoutny@xxxxxxxx>
---
Documentation/admin-guide/cgroup-v2.rst | 9 +++--
kernel/cgroup/pids.c | 46 ++++++++++++++++---------
2 files changed, 36 insertions(+), 19 deletions(-)
diff --git a/Documentation/admin-guide/cgroup-v2.rst b/Documentation/admin-guide/cgroup-v2.rst
index 945ff743a3c9..0b5f77104e8b 100644
--- a/Documentation/admin-guide/cgroup-v2.rst
+++ b/Documentation/admin-guide/cgroup-v2.rst
@@ -240,8 +240,11 @@ cgroup v2 currently supports the following mount options.
v2 is remounted later on).
pids_localevents
- Represent fork failures inside cgroup's pids.events:max (v1 behavior),
- not its limit being hit (v2 behavior).
+ The option restores v1-like behavior of pids.events:max, that is only
+ local (inside cgroup proper) fork failures are counted. Without this
+ option pids.events.max represents any pids.max enforcemnt across
+ cgroup's subtree.
+
Organizing Processes and Threads
@@ -2205,7 +2208,7 @@ PID Interface Files
modified event. The following entries are defined.
max
- The number of times the cgroup's number of processes hit the
+ The number of times the cgroup's total number of processes hit the pids.max
limit (see also pids_localevents).
Organisational operations are not blocked by cgroup policies, so it is
diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c
index a557f5c8300b..c09b744d548c 100644
--- a/kernel/cgroup/pids.c
+++ b/kernel/cgroup/pids.c
@@ -238,6 +238,34 @@ static void pids_cancel_attach(struct cgroup_taskset *tset)
}
}
+static void pids_event(struct pids_cgroup *pids_forking,
+ struct pids_cgroup *pids_over_limit)
+{
+ struct pids_cgroup *p = pids_forking;
+ bool limit = false;
+
+ for (; parent_pids(p); p = parent_pids(p)) {
+ /* Only log the first time limit is hit. */
+ if (atomic64_inc_return(&p->events[PIDCG_FORKFAIL]) == 1) {
+ pr_info("cgroup: fork rejected by pids controller in ");
+ pr_cont_cgroup_path(p->css.cgroup);
+ pr_cont("\n");
+ }
+ cgroup_file_notify(&p->events_file);
+
+ if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
+ cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
+ break;
+
+ if (p == pids_over_limit)
+ limit = true;
+ if (limit)
+ atomic64_inc(&p->events[PIDCG_MAX]);
+
+ cgroup_file_notify(&p->events_file);
+ }
+}
+
/*
* task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
* on cgroup_threadgroup_change_begin() held by the copy_process().
@@ -254,23 +282,9 @@ static int pids_can_fork(struct task_struct *task, struct css_set *cset)
css = task_css_check(current, pids_cgrp_id, true);
pids = css_pids(css);
err = pids_try_charge(pids, 1, &pids_over_limit);
- if (err) {
- /* compatibility on v1 where events were notified in leaves. */
- if (!cgroup_subsys_on_dfl(pids_cgrp_subsys))
- pids_over_limit = pids;
-
- /* Only log the first time limit is hit. */
- if (atomic64_inc_return(&pids->events[PIDCG_FORKFAIL]) == 1) {
- pr_info("cgroup: fork rejected by pids controller in ");
- pr_cont_cgroup_path(pids->css.cgroup);
- pr_cont("\n");
- }
- atomic64_inc(&pids_over_limit->events[PIDCG_MAX]);
+ if (err)
+ pids_event(pids, pids_over_limit);
- cgroup_file_notify(&pids->events_file);
- if (pids_over_limit != pids)
- cgroup_file_notify(&pids_over_limit->events_file);
- }
return err;
}
--
2.44.0
