linux/arch/s390/numa/toptree.c

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/*
* NUMA support for s390
*
* A tree structure used for machine topology mangling
*
* Copyright IBM Corp. 2015
*/
#include <linux/kernel.h>
#include <linux/cpumask.h>
#include <linux/list.h>
#include <linux/list_sort.h>
#include <linux/slab.h>
#include <asm/numa.h>
#include "toptree.h"
/**
* toptree_alloc - Allocate and initialize a new tree node.
* @level: The node's vertical level; level 0 contains the leaves.
* @id: ID number, explicitly not unique beyond scope of node's siblings
*
* Allocate a new tree node and initialize it.
*
* RETURNS:
* Pointer to the new tree node or NULL on error
*/
struct toptree *toptree_alloc(int level, int id)
{
struct toptree *res = kzalloc(sizeof(struct toptree), GFP_KERNEL);
if (!res)
return res;
INIT_LIST_HEAD(&res->children);
INIT_LIST_HEAD(&res->sibling);
cpumask_clear(&res->mask);
res->level = level;
res->id = id;
return res;
}
/**
* toptree_remove - Remove a tree node from a tree
* @cand: Pointer to the node to remove
*
* The node is detached from its parent node. The parent node's
* masks will be updated to reflect the loss of the child.
*/
static void toptree_remove(struct toptree *cand)
{
struct toptree *oldparent;
list_del_init(&cand->sibling);
oldparent = cand->parent;
cand->parent = NULL;
toptree_update_mask(oldparent);
}
/**
* toptree_free - discard a tree node
* @cand: Pointer to the tree node to discard
*
* Checks if @cand is attached to a parent node. Detaches it
* cleanly using toptree_remove. Possible children are freed
* recursively. In the end @cand itself is freed.
*/
void toptree_free(struct toptree *cand)
{
struct toptree *child, *tmp;
if (cand->parent)
toptree_remove(cand);
toptree_for_each_child_safe(child, tmp, cand)
toptree_free(child);
kfree(cand);
}
/**
* toptree_update_mask - Update node bitmasks
* @cand: Pointer to a tree node
*
* The node's cpumask will be updated by combining all children's
* masks. Then toptree_update_mask is called recursively for the
* parent if applicable.
*
* NOTE:
* This must not be called on leaves. If called on a leaf, its
* CPU mask is cleared and lost.
*/
void toptree_update_mask(struct toptree *cand)
{
struct toptree *child;
cpumask_clear(&cand->mask);
list_for_each_entry(child, &cand->children, sibling)
cpumask_or(&cand->mask, &cand->mask, &child->mask);
if (cand->parent)
toptree_update_mask(cand->parent);
}
/**
* toptree_insert - Insert a tree node into tree
* @cand: Pointer to the node to insert
* @target: Pointer to the node to which @cand will added as a child
*
* Insert a tree node into a tree. Masks will be updated automatically.
*
* RETURNS:
* 0 on success, -1 if NULL is passed as argument or the node levels
* don't fit.
*/
static int toptree_insert(struct toptree *cand, struct toptree *target)
{
if (!cand || !target)
return -1;
if (target->level != (cand->level + 1))
return -1;
list_add_tail(&cand->sibling, &target->children);
cand->parent = target;
toptree_update_mask(target);
return 0;
}
/**
* toptree_move_children - Move all child nodes of a node to a new place
* @cand: Pointer to the node whose children are to be moved
* @target: Pointer to the node to which @cand's children will be attached
*
* Take all child nodes of @cand and move them using toptree_move.
*/
static void toptree_move_children(struct toptree *cand, struct toptree *target)
{
struct toptree *child, *tmp;
toptree_for_each_child_safe(child, tmp, cand)
toptree_move(child, target);
}
/**
* toptree_unify - Merge children with same ID
* @cand: Pointer to node whose direct children should be made unique
*
* When mangling the tree it is possible that a node has two or more children
* which have the same ID. This routine merges these children into one and
* moves all children of the merged nodes into the unified node.
*/
void toptree_unify(struct toptree *cand)
{
struct toptree *child, *tmp, *cand_copy;
/* Threads cannot be split, cores are not split */
if (cand->level < 2)
return;
cand_copy = toptree_alloc(cand->level, 0);
toptree_for_each_child_safe(child, tmp, cand) {
struct toptree *tmpchild;
if (!cpumask_empty(&child->mask)) {
tmpchild = toptree_get_child(cand_copy, child->id);
toptree_move_children(child, tmpchild);
}
toptree_free(child);
}
toptree_move_children(cand_copy, cand);
toptree_free(cand_copy);
toptree_for_each_child(child, cand)
toptree_unify(child);
}
/**
* toptree_move - Move a node to another context
* @cand: Pointer to the node to move
* @target: Pointer to the node where @cand should go
*
* In the easiest case @cand is exactly on the level below @target
* and will be immediately moved to the target.
*
* If @target's level is not the direct parent level of @cand,
* nodes for the missing levels are created and put between
* @cand and @target. The "stacking" nodes' IDs are taken from
* @cand's parents.
*
* After this it is likely to have redundant nodes in the tree
* which are addressed by means of toptree_unify.
*/
void toptree_move(struct toptree *cand, struct toptree *target)
{
struct toptree *stack_target, *real_insert_point, *ptr, *tmp;
if (cand->level + 1 == target->level) {
toptree_remove(cand);
toptree_insert(cand, target);
return;
}
real_insert_point = NULL;
ptr = cand;
stack_target = NULL;
do {
tmp = stack_target;
stack_target = toptree_alloc(ptr->level + 1,
ptr->parent->id);
toptree_insert(tmp, stack_target);
if (!real_insert_point)
real_insert_point = stack_target;
ptr = ptr->parent;
} while (stack_target->level < (target->level - 1));
toptree_remove(cand);
toptree_insert(cand, real_insert_point);
toptree_insert(stack_target, target);
}
/**
* toptree_get_child - Access a tree node's child by its ID
* @cand: Pointer to tree node whose child is to access
* @id: The desired child's ID
*
* @cand's children are searched for a child with matching ID.
* If no match can be found, a new child with the desired ID
* is created and returned.
*/
struct toptree *toptree_get_child(struct toptree *cand, int id)
{
struct toptree *child;
toptree_for_each_child(child, cand)
if (child->id == id)
return child;
child = toptree_alloc(cand->level-1, id);
toptree_insert(child, cand);
return child;
}
/**
* toptree_first - Find the first descendant on specified level
* @context: Pointer to tree node whose descendants are to be used
* @level: The level of interest
*
* RETURNS:
* @context's first descendant on the specified level, or NULL
* if there is no matching descendant
*/
struct toptree *toptree_first(struct toptree *context, int level)
{
struct toptree *child, *tmp;
if (context->level == level)
return context;
if (!list_empty(&context->children)) {
list_for_each_entry(child, &context->children, sibling) {
tmp = toptree_first(child, level);
if (tmp)
return tmp;
}
}
return NULL;
}
/**
* toptree_next_sibling - Return next sibling
* @cur: Pointer to a tree node
*
* RETURNS:
* If @cur has a parent and is not the last in the parent's children list,
* the next sibling is returned. Or NULL when there are no siblings left.
*/
static struct toptree *toptree_next_sibling(struct toptree *cur)
{
if (cur->parent == NULL)
return NULL;
if (cur == list_last_entry(&cur->parent->children,
struct toptree, sibling))
return NULL;
return (struct toptree *) list_next_entry(cur, sibling);
}
/**
* toptree_next - Tree traversal function
* @cur: Pointer to current element
* @context: Pointer to the root node of the tree or subtree to
* be traversed.
* @level: The level of interest.
*
* RETURNS:
* Pointer to the next node on level @level
* or NULL when there is no next node.
*/
struct toptree *toptree_next(struct toptree *cur, struct toptree *context,
int level)
{
struct toptree *cur_context, *tmp;
if (!cur)
return NULL;
if (context->level == level)
return NULL;
tmp = toptree_next_sibling(cur);
if (tmp != NULL)
return tmp;
cur_context = cur;
while (cur_context->level < context->level - 1) {
/* Step up */
cur_context = cur_context->parent;
/* Step aside */
tmp = toptree_next_sibling(cur_context);
if (tmp != NULL) {
/* Step down */
tmp = toptree_first(tmp, level);
if (tmp != NULL)
return tmp;
}
}
return NULL;
}
/**
* toptree_count - Count descendants on specified level
* @context: Pointer to node whose descendants are to be considered
* @level: Only descendants on the specified level will be counted
*
* RETURNS:
* Number of descendants on the specified level
*/
int toptree_count(struct toptree *context, int level)
{
struct toptree *cur;
int cnt = 0;
toptree_for_each(cur, context, level)
cnt++;
return cnt;
}