diff options
| -rw-r--r-- | kernel/cgroup/rstat.c | 42 |
1 files changed, 33 insertions, 9 deletions
diff --git a/kernel/cgroup/rstat.c b/kernel/cgroup/rstat.c index 4d5fd8d12bdd..357c538d14da 100644 --- a/kernel/cgroup/rstat.c +++ b/kernel/cgroup/rstat.c @@ -144,30 +144,54 @@ __bpf_kfunc void css_rstat_updated(struct cgroup_subsys_state *css, int cpu) * @head: current head of the list (= subtree root) * @child: first child of the root * @cpu: target cpu - * Return: A new singly linked list of cgroups to be flush + * Return: A new singly linked list of cgroups to be flushed * * Iteratively traverse down the cgroup_rstat_cpu updated tree level by * level and push all the parents first before their next level children - * into a singly linked list built from the tail backward like "pushing" - * cgroups into a stack. The root is pushed by the caller. + * into a singly linked list via the rstat_flush_next pointer built from the + * tail backward like "pushing" cgroups into a stack. The root is pushed by + * the caller. */ static struct cgroup *cgroup_rstat_push_children(struct cgroup *head, struct cgroup *child, int cpu) { - struct cgroup *chead = child; /* Head of child cgroup level */ + struct cgroup *cnext = child; /* Next head of child cgroup level */ struct cgroup *ghead = NULL; /* Head of grandchild cgroup level */ struct cgroup *parent, *grandchild; struct cgroup_rstat_cpu *crstatc; child->rstat_flush_next = NULL; + /* + * The cgroup_rstat_lock must be held for the whole duration from + * here as the rstat_flush_next list is being constructed to when + * it is consumed later in css_rstat_flush(). + */ + lockdep_assert_held(&cgroup_rstat_lock); + + /* + * Notation: -> updated_next pointer + * => rstat_flush_next pointer + * + * Assuming the following sample updated_children lists: + * P: C1 -> C2 -> P + * C1: G11 -> G12 -> C1 + * C2: G21 -> G22 -> C2 + * + * After 1st iteration: + * head => C2 => C1 => NULL + * ghead => G21 => G11 => NULL + * + * After 2nd iteration: + * head => G12 => G11 => G22 => G21 => C2 => C1 => NULL + */ next_level: - while (chead) { - child = chead; - chead = child->rstat_flush_next; + while (cnext) { + child = cnext; + cnext = child->rstat_flush_next; parent = cgroup_parent(child); - /* updated_next is parent cgroup terminated */ + /* updated_next is parent cgroup terminated if !NULL */ while (child != parent) { child->rstat_flush_next = head; head = child; @@ -185,7 +209,7 @@ next_level: } if (ghead) { - chead = ghead; + cnext = ghead; ghead = NULL; goto next_level; } |