1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * NUMA support for s390
4 *
5 * A tree structure used for machine topology mangling
6 *
7 * Copyright IBM Corp. 2015
8 */
9
10 #include <linux/kernel.h>
11 #include <linux/memblock.h>
12 #include <linux/cpumask.h>
13 #include <linux/list.h>
14 #include <linux/list_sort.h>
15 #include <linux/slab.h>
16 #include <asm/numa.h>
17
18 #include "toptree.h"
19
20 /**
21 * toptree_alloc - Allocate and initialize a new tree node.
22 * @level: The node's vertical level; level 0 contains the leaves.
23 * @id: ID number, explicitly not unique beyond scope of node's siblings
24 *
25 * Allocate a new tree node and initialize it.
26 *
27 * RETURNS:
28 * Pointer to the new tree node or NULL on error
29 */
30 struct toptree __ref *toptree_alloc(int level, int id)
31 {
32 struct toptree *res;
33
34 if (slab_is_available())
35 res = kzalloc(sizeof(*res), GFP_KERNEL);
36 else
37 res = memblock_alloc(sizeof(*res), 8);
38 if (!res)
39 return res;
40
41 INIT_LIST_HEAD(&res->children);
42 INIT_LIST_HEAD(&res->sibling);
43 cpumask_clear(&res->mask);
44 res->level = level;
45 res->id = id;
46 return res;
47 }
48
49 /**
50 * toptree_remove - Remove a tree node from a tree
51 * @cand: Pointer to the node to remove
52 *
53 * The node is detached from its parent node. The parent node's
54 * masks will be updated to reflect the loss of the child.
55 */
56 static void toptree_remove(struct toptree *cand)
57 {
58 struct toptree *oldparent;
59
60 list_del_init(&cand->sibling);
61 oldparent = cand->parent;
62 cand->parent = NULL;
63 toptree_update_mask(oldparent);
64 }
65
66 /**
67 * toptree_free - discard a tree node
68 * @cand: Pointer to the tree node to discard
69 *
70 * Checks if @cand is attached to a parent node. Detaches it
71 * cleanly using toptree_remove. Possible children are freed
72 * recursively. In the end @cand itself is freed.
73 */
74 void __ref toptree_free(struct toptree *cand)
75 {
76 struct toptree *child, *tmp;
77
78 if (cand->parent)
79 toptree_remove(cand);
80 toptree_for_each_child_safe(child, tmp, cand)
81 toptree_free(child);
82 if (slab_is_available())
83 kfree(cand);
84 else
85 memblock_free_early((unsigned long)cand, sizeof(*cand));
86 }
87
88 /**
89 * toptree_update_mask - Update node bitmasks
90 * @cand: Pointer to a tree node
91 *
92 * The node's cpumask will be updated by combining all children's
93 * masks. Then toptree_update_mask is called recursively for the
94 * parent if applicable.
95 *
96 * NOTE:
97 * This must not be called on leaves. If called on a leaf, its
98 * CPU mask is cleared and lost.
99 */
100 void toptree_update_mask(struct toptree *cand)
101 {
102 struct toptree *child;
103
104 cpumask_clear(&cand->mask);
105 list_for_each_entry(child, &cand->children, sibling)
106 cpumask_or(&cand->mask, &cand->mask, &child->mask);
107 if (cand->parent)
108 toptree_update_mask(cand->parent);
109 }
110
111 /**
112 * toptree_insert - Insert a tree node into tree
113 * @cand: Pointer to the node to insert
114 * @target: Pointer to the node to which @cand will added as a child
115 *
116 * Insert a tree node into a tree. Masks will be updated automatically.
117 *
118 * RETURNS:
119 * 0 on success, -1 if NULL is passed as argument or the node levels
120 * don't fit.
121 */
122 static int toptree_insert(struct toptree *cand, struct toptree *target)
123 {
124 if (!cand || !target)
125 return -1;
126 if (target->level != (cand->level + 1))
127 return -1;
128 list_add_tail(&cand->sibling, &target->children);
129 cand->parent = target;
130 toptree_update_mask(target);
131 return 0;
132 }
133
134 /**
135 * toptree_move_children - Move all child nodes of a node to a new place
136 * @cand: Pointer to the node whose children are to be moved
137 * @target: Pointer to the node to which @cand's children will be attached
138 *
139 * Take all child nodes of @cand and move them using toptree_move.
140 */
141 static void toptree_move_children(struct toptree *cand, struct toptree *target)
142 {
143 struct toptree *child, *tmp;
144
145 toptree_for_each_child_safe(child, tmp, cand)
146 toptree_move(child, target);
147 }
148
149 /**
150 * toptree_unify - Merge children with same ID
151 * @cand: Pointer to node whose direct children should be made unique
152 *
153 * When mangling the tree it is possible that a node has two or more children
154 * which have the same ID. This routine merges these children into one and
155 * moves all children of the merged nodes into the unified node.
156 */
157 void toptree_unify(struct toptree *cand)
158 {
159 struct toptree *child, *tmp, *cand_copy;
160
161 /* Threads cannot be split, cores are not split */
162 if (cand->level < 2)
163 return;
164
165 cand_copy = toptree_alloc(cand->level, 0);
166 toptree_for_each_child_safe(child, tmp, cand) {
167 struct toptree *tmpchild;
168
169 if (!cpumask_empty(&child->mask)) {
170 tmpchild = toptree_get_child(cand_copy, child->id);
171 toptree_move_children(child, tmpchild);
172 }
173 toptree_free(child);
174 }
175 toptree_move_children(cand_copy, cand);
176 toptree_free(cand_copy);
177
178 toptree_for_each_child(child, cand)
179 toptree_unify(child);
180 }
181
182 /**
183 * toptree_move - Move a node to another context
184 * @cand: Pointer to the node to move
185 * @target: Pointer to the node where @cand should go
186 *
187 * In the easiest case @cand is exactly on the level below @target
188 * and will be immediately moved to the target.
189 *
190 * If @target's level is not the direct parent level of @cand,
191 * nodes for the missing levels are created and put between
192 * @cand and @target. The "stacking" nodes' IDs are taken from
193 * @cand's parents.
194 *
195 * After this it is likely to have redundant nodes in the tree
196 * which are addressed by means of toptree_unify.
197 */
198 void toptree_move(struct toptree *cand, struct toptree *target)
199 {
200 struct toptree *stack_target, *real_insert_point, *ptr, *tmp;
201
202 if (cand->level + 1 == target->level) {
203 toptree_remove(cand);
204 toptree_insert(cand, target);
205 return;
206 }
207
208 real_insert_point = NULL;
209 ptr = cand;
210 stack_target = NULL;
211
212 do {
213 tmp = stack_target;
214 stack_target = toptree_alloc(ptr->level + 1,
215 ptr->parent->id);
216 toptree_insert(tmp, stack_target);
217 if (!real_insert_point)
218 real_insert_point = stack_target;
219 ptr = ptr->parent;
220 } while (stack_target->level < (target->level - 1));
221
222 toptree_remove(cand);
223 toptree_insert(cand, real_insert_point);
224 toptree_insert(stack_target, target);
225 }
226
227 /**
228 * toptree_get_child - Access a tree node's child by its ID
229 * @cand: Pointer to tree node whose child is to access
230 * @id: The desired child's ID
231 *
232 * @cand's children are searched for a child with matching ID.
233 * If no match can be found, a new child with the desired ID
234 * is created and returned.
235 */
236 struct toptree *toptree_get_child(struct toptree *cand, int id)
237 {
238 struct toptree *child;
239
240 toptree_for_each_child(child, cand)
241 if (child->id == id)
242 return child;
243 child = toptree_alloc(cand->level-1, id);
244 toptree_insert(child, cand);
245 return child;
246 }
247
248 /**
249 * toptree_first - Find the first descendant on specified level
250 * @context: Pointer to tree node whose descendants are to be used
251 * @level: The level of interest
252 *
253 * RETURNS:
254 * @context's first descendant on the specified level, or NULL
255 * if there is no matching descendant
256 */
257 struct toptree *toptree_first(struct toptree *context, int level)
258 {
259 struct toptree *child, *tmp;
260
261 if (context->level == level)
262 return context;
263
264 if (!list_empty(&context->children)) {
265 list_for_each_entry(child, &context->children, sibling) {
266 tmp = toptree_first(child, level);
267 if (tmp)
268 return tmp;
269 }
270 }
271 return NULL;
272 }
273
274 /**
275 * toptree_next_sibling - Return next sibling
276 * @cur: Pointer to a tree node
277 *
278 * RETURNS:
279 * If @cur has a parent and is not the last in the parent's children list,
280 * the next sibling is returned. Or NULL when there are no siblings left.
281 */
282 static struct toptree *toptree_next_sibling(struct toptree *cur)
283 {
284 if (cur->parent == NULL)
285 return NULL;
286
287 if (cur == list_last_entry(&cur->parent->children,
288 struct toptree, sibling))
289 return NULL;
290 return (struct toptree *) list_next_entry(cur, sibling);
291 }
292
293 /**
294 * toptree_next - Tree traversal function
295 * @cur: Pointer to current element
296 * @context: Pointer to the root node of the tree or subtree to
297 * be traversed.
298 * @level: The level of interest.
299 *
300 * RETURNS:
301 * Pointer to the next node on level @level
302 * or NULL when there is no next node.
303 */
304 struct toptree *toptree_next(struct toptree *cur, struct toptree *context,
305 int level)
306 {
307 struct toptree *cur_context, *tmp;
308
309 if (!cur)
310 return NULL;
311
312 if (context->level == level)
313 return NULL;
314
315 tmp = toptree_next_sibling(cur);
316 if (tmp != NULL)
317 return tmp;
318
319 cur_context = cur;
320 while (cur_context->level < context->level - 1) {
321 /* Step up */
322 cur_context = cur_context->parent;
323 /* Step aside */
324 tmp = toptree_next_sibling(cur_context);
325 if (tmp != NULL) {
326 /* Step down */
327 tmp = toptree_first(tmp, level);
328 if (tmp != NULL)
329 return tmp;
330 }
331 }
332 return NULL;
333 }
334
335 /**
336 * toptree_count - Count descendants on specified level
337 * @context: Pointer to node whose descendants are to be considered
338 * @level: Only descendants on the specified level will be counted
339 *
340 * RETURNS:
341 * Number of descendants on the specified level
342 */
343 int toptree_count(struct toptree *context, int level)
344 {
345 struct toptree *cur;
346 int cnt = 0;
347
348 toptree_for_each(cur, context, level)
349 cnt++;
350 return cnt;
351 }