From: Xiu Jianfeng <xiujianfeng@xxxxxxxxxx>
Currently when a process in a group forks and fails due to it's
parent's max restriction, all the cgroups from 'pids_forking' to root
will generate event notifications but only the cgroups from
'pids_over_limit' to root will increase the counter of PIDCG_MAX.
Consider this scenario: there are 4 groups A, B, C,and D, the
relationships are as follows, and user is watching on C.pids.events.
root->A->B->C->D
When a process in D forks and fails due to B.max restriction, the
user will get a spurious event notification because when he wakes up
and reads C.pids.events, he will find that the content has not changed.
To address this issue, only the cgroups from 'pids_over_limit' to root
will have their PIDCG_MAX counters increased and event notifications
generated.
Fixes: 385a635cacfe ("cgroup/pids: Make event counters hierarchical")
Signed-off-by: Xiu Jianfeng <xiujianfeng@xxxxxxxxxx>
---
v2: add Fixes tag and fix a extra notification
---
kernel/cgroup/pids.c | 18 +++++++-----------
1 file changed, 7 insertions(+), 11 deletions(-)
diff --git a/kernel/cgroup/pids.c b/kernel/cgroup/pids.c
index f5cb0ec45b9d..34aa63d7c9c6 100644
--- a/kernel/cgroup/pids.c
+++ b/kernel/cgroup/pids.c
@@ -244,7 +244,6 @@ static void pids_event(struct pids_cgroup *pids_forking,
struct pids_cgroup *pids_over_limit)
{
struct pids_cgroup *p = pids_forking;
- bool limit = false;
/* Only log the first time limit is hit. */
if (atomic64_inc_return(&p->events_local[PIDCG_FORKFAIL]) == 1) {
@@ -252,20 +251,17 @@ static void pids_event(struct pids_cgroup *pids_forking,
pr_cont_cgroup_path(p->css.cgroup);
pr_cont("\n");
}
- cgroup_file_notify(&p->events_local_file);
if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
- cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS)
+ cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
+ cgroup_file_notify(&p->events_local_file);
return;
+ }
- for (; parent_pids(p); p = parent_pids(p)) {
- if (p == pids_over_limit) {
- limit = true;
- atomic64_inc(&p->events_local[PIDCG_MAX]);
- cgroup_file_notify(&p->events_local_file);
- }
- if (limit)
- atomic64_inc(&p->events[PIDCG_MAX]);
+ atomic64_inc(&pids_over_limit->events_local[PIDCG_MAX]);
+ cgroup_file_notify(&pids_over_limit->events_local_file);
+ for (p = pids_over_limit; parent_pids(p); p = parent_pids(p)) {
+ atomic64_inc(&p->events[PIDCG_MAX]);
cgroup_file_notify(&p->events_file);
}
}
--
2.34.1
