}
/**
- * cgroup_rstat_cpu_pop_updated - iterate and dismantle rstat_cpu updated tree
- * @pos: current position
- * @root: root of the tree to traversal
+ * cgroup_rstat_push_children - push children cgroups into the given list
+ * @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
*
- * Walks the updated rstat_cpu tree on @cpu from @root. %NULL @pos starts
- * the traversal and %NULL return indicates the end. During traversal,
- * each returned cgroup is unlinked from the tree. Must be called with the
- * matching cgroup_rstat_cpu_lock held.
+ * 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.
+ */
+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 *ghead = NULL; /* Head of grandchild cgroup level */
+ struct cgroup *parent, *grandchild;
+ struct cgroup_rstat_cpu *crstatc;
+
+ child->rstat_flush_next = NULL;
+
+next_level:
+ while (chead) {
+ child = chead;
+ chead = child->rstat_flush_next;
+ parent = cgroup_parent(child);
+
+ /* updated_next is parent cgroup terminated */
+ while (child != parent) {
+ child->rstat_flush_next = head;
+ head = child;
+ crstatc = cgroup_rstat_cpu(child, cpu);
+ grandchild = crstatc->updated_children;
+ if (grandchild != child) {
+ /* Push the grand child to the next level */
+ crstatc->updated_children = child;
+ grandchild->rstat_flush_next = ghead;
+ ghead = grandchild;
+ }
+ child = crstatc->updated_next;
+ crstatc->updated_next = NULL;
+ }
+ }
+
+ if (ghead) {
+ chead = ghead;
+ ghead = NULL;
+ goto next_level;
+ }
+ return head;
+}
+
+/**
+ * cgroup_rstat_updated_list - return a list of updated cgroups to be flushed
+ * @root: root of the cgroup subtree to traverse
+ * @cpu: target cpu
+ * Return: A singly linked list of cgroups to be flushed
+ *
+ * Walks the updated rstat_cpu tree on @cpu from @root. During traversal,
+ * each returned cgroup is unlinked from the updated tree.
*
* The only ordering guarantee is that, for a parent and a child pair
- * covered by a given traversal, if a child is visited, its parent is
- * guaranteed to be visited afterwards.
+ * covered by a given traversal, the child is before its parent in
+ * the list.
+ *
+ * Note that updated_children is self terminated and points to a list of
+ * child cgroups if not empty. Whereas updated_next is like a sibling link
+ * within the children list and terminated by the parent cgroup. An exception
+ * here is the cgroup root whose updated_next can be self terminated.
*/
-static struct cgroup *cgroup_rstat_cpu_pop_updated(struct cgroup *pos,
- struct cgroup *root, int cpu)
+static struct cgroup *cgroup_rstat_updated_list(struct cgroup *root, int cpu)
{
- struct cgroup_rstat_cpu *rstatc;
- struct cgroup *parent;
-
- if (pos == root)
- return NULL;
+ raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock, cpu);
+ struct cgroup_rstat_cpu *rstatc = cgroup_rstat_cpu(root, cpu);
+ struct cgroup *head = NULL, *parent, *child;
+ unsigned long flags;
/*
- * We're gonna walk down to the first leaf and visit/remove it. We
- * can pick whatever unvisited node as the starting point.
+ * The _irqsave() is needed because cgroup_rstat_lock is
+ * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring
+ * this lock with the _irq() suffix only disables interrupts on
+ * a non-PREEMPT_RT kernel. The raw_spinlock_t below disables
+ * interrupts on both configurations. The _irqsave() ensures
+ * that interrupts are always disabled and later restored.
*/
- if (!pos) {
- pos = root;
- /* return NULL if this subtree is not on-list */
- if (!cgroup_rstat_cpu(pos, cpu)->updated_next)
- return NULL;
- } else {
- pos = cgroup_parent(pos);
- }
+ raw_spin_lock_irqsave(cpu_lock, flags);
- /* walk down to the first leaf */
- while (true) {
- rstatc = cgroup_rstat_cpu(pos, cpu);
- if (rstatc->updated_children == pos)
- break;
- pos = rstatc->updated_children;
- }
+ /* Return NULL if this subtree is not on-list */
+ if (!rstatc->updated_next)
+ goto unlock_ret;
/*
- * Unlink @pos from the tree. As the updated_children list is
+ * Unlink @root from its parent. As the updated_children list is
* singly linked, we have to walk it to find the removal point.
- * However, due to the way we traverse, @pos will be the first
- * child in most cases. The only exception is @root.
*/
- parent = cgroup_parent(pos);
+ parent = cgroup_parent(root);
if (parent) {
struct cgroup_rstat_cpu *prstatc;
struct cgroup **nextp;
prstatc = cgroup_rstat_cpu(parent, cpu);
nextp = &prstatc->updated_children;
- while (*nextp != pos) {
+ while (*nextp != root) {
struct cgroup_rstat_cpu *nrstatc;
nrstatc = cgroup_rstat_cpu(*nextp, cpu);
}
rstatc->updated_next = NULL;
- return pos;
+
+ /* Push @root to the list first before pushing the children */
+ head = root;
+ root->rstat_flush_next = NULL;
+ child = rstatc->updated_children;
+ rstatc->updated_children = root;
+ if (child != root)
+ head = cgroup_rstat_push_children(head, child, cpu);
+unlock_ret:
+ raw_spin_unlock_irqrestore(cpu_lock, flags);
+ return head;
}
/*
lockdep_assert_held(&cgroup_rstat_lock);
for_each_possible_cpu(cpu) {
- raw_spinlock_t *cpu_lock = per_cpu_ptr(&cgroup_rstat_cpu_lock,
- cpu);
- struct cgroup *pos = NULL;
- unsigned long flags;
+ struct cgroup *pos = cgroup_rstat_updated_list(cgrp, cpu);
- /*
- * The _irqsave() is needed because cgroup_rstat_lock is
- * spinlock_t which is a sleeping lock on PREEMPT_RT. Acquiring
- * this lock with the _irq() suffix only disables interrupts on
- * a non-PREEMPT_RT kernel. The raw_spinlock_t below disables
- * interrupts on both configurations. The _irqsave() ensures
- * that interrupts are always disabled and later restored.
- */
- raw_spin_lock_irqsave(cpu_lock, flags);
- while ((pos = cgroup_rstat_cpu_pop_updated(pos, cgrp, cpu))) {
+ for (; pos; pos = pos->rstat_flush_next) {
struct cgroup_subsys_state *css;
cgroup_base_stat_flush(pos, cpu);
css->ss->css_rstat_flush(css, cpu);
rcu_read_unlock();
}
- raw_spin_unlock_irqrestore(cpu_lock, flags);
/* play nice and yield if necessary */
if (need_resched() || spin_needbreak(&cgroup_rstat_lock)) {
projects / linux-2.6-microblaze.git / blobdiff