1 /* Copyright (C) 2015-2023 Free Software Foundation, Inc.
2 Contributed by Aldy Hernandez <aldyh@redhat.com>.
3
4 This file is part of the GNU Offloading and Multi Processing Library
5 (libgomp).
6
7 Libgomp is free software; you can redistribute it and/or modify it
8 under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3, or (at your option)
10 any later version.
11
12 Libgomp is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
14 FOR A PARTICULAR PURPOSE. See the GNU General Public License for
15 more details.
16
17 Under Section 7 of GPL version 3, you are granted additional
18 permissions described in the GCC Runtime Library Exception, version
19 3.1, as published by the Free Software Foundation.
20
21 You should have received a copy of the GNU General Public License and
22 a copy of the GCC Runtime Library Exception along with this program;
23 see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 <http://www.gnu.org/licenses/>. */
25
26 /* Priority queue implementation of GOMP tasks. */
27
28 #include "libgomp.h"
29
30 #if _LIBGOMP_CHECKING_
31 #include <stdio.h>
32
33 /* Sanity check to verify whether a TASK is in LIST. Return TRUE if
34 found, FALSE otherwise.
35
36 TYPE is the type of priority queue this task resides in. */
37
38 static inline bool
39 priority_queue_task_in_list_p (enum priority_queue_type type,
40 struct priority_list *list,
41 struct gomp_task *task)
42 {
43 struct priority_node *p = list->tasks;
44 do
45 {
46 if (priority_node_to_task (type, p) == task)
47 return true;
48 p = p->next;
49 }
50 while (p != list->tasks);
51 return false;
52 }
53
54 /* Tree version of priority_queue_task_in_list_p. */
55
56 static inline bool
57 priority_queue_task_in_tree_p (enum priority_queue_type type,
58 struct priority_queue *head,
59 struct gomp_task *task)
60 {
61 struct priority_list *list
62 = priority_queue_lookup_priority (head, task->priority);
63 if (!list)
64 return false;
65 return priority_queue_task_in_list_p (type, list, task);
66 }
67
68 /* Generic version of priority_queue_task_in_list_p that works for
69 trees or lists. */
70
71 bool
72 priority_queue_task_in_queue_p (enum priority_queue_type type,
73 struct priority_queue *head,
74 struct gomp_task *task)
75 {
76 if (priority_queue_empty_p (head, MEMMODEL_RELAXED))
77 return false;
78 if (priority_queue_multi_p (head))
79 return priority_queue_task_in_tree_p (type, head, task);
80 else
81 return priority_queue_task_in_list_p (type, &head->l, task);
82 }
83
84 /* Sanity check LIST to make sure the tasks therein are in the right
85 order. LIST is a priority list of type TYPE.
86
87 The expected order is that GOMP_TASK_WAITING tasks come before
88 GOMP_TASK_TIED/GOMP_TASK_ASYNC_RUNNING ones.
89
90 If CHECK_DEPS is TRUE, we also check that parent_depends_on WAITING
91 tasks come before !parent_depends_on WAITING tasks. This is only
92 applicable to the children queue, and the caller is expected to
93 ensure that we are verifying the children queue. */
94
95 static void
96 priority_list_verify (enum priority_queue_type type,
97 struct priority_list *list, bool check_deps)
98 {
99 bool seen_tied = false;
100 bool seen_plain_waiting = false;
101 struct priority_node *p = list->tasks;
102 while (1)
103 {
104 struct gomp_task *t = priority_node_to_task (type, p);
105 if (seen_tied && t->kind == GOMP_TASK_WAITING)
106 gomp_fatal ("priority_queue_verify: WAITING task after TIED");
107 if (t->kind >= GOMP_TASK_TIED)
108 seen_tied = true;
109 else if (check_deps && t->kind == GOMP_TASK_WAITING)
110 {
111 if (t->parent_depends_on)
112 {
113 if (seen_plain_waiting)
114 gomp_fatal ("priority_queue_verify: "
115 "parent_depends_on after !parent_depends_on");
116 }
117 else
118 seen_plain_waiting = true;
119 }
120 p = p->next;
121 if (p == list->tasks)
122 break;
123 }
124 }
125
126 /* Callback type for priority_tree_verify_callback. */
127 struct cbtype
128 {
129 enum priority_queue_type type;
130 bool check_deps;
131 };
132
133 /* Verify every task in NODE.
134
135 Callback for splay_tree_foreach. */
136
137 static void
138 priority_tree_verify_callback (prio_splay_tree_key key, void *data)
139 {
140 struct cbtype *cb = (struct cbtype *) data;
141 priority_list_verify (cb->type, &key->l, cb->check_deps);
142 }
143
144 /* Generic version of priority_list_verify.
145
146 Sanity check HEAD to make sure the tasks therein are in the right
147 order. The priority_queue holds tasks of type TYPE.
148
149 If CHECK_DEPS is TRUE, we also check that parent_depends_on WAITING
150 tasks come before !parent_depends_on WAITING tasks. This is only
151 applicable to the children queue, and the caller is expected to
152 ensure that we are verifying the children queue. */
153
154 void
155 priority_queue_verify (enum priority_queue_type type,
156 struct priority_queue *head, bool check_deps)
157 {
158 if (priority_queue_empty_p (head, MEMMODEL_RELAXED))
159 return;
160 if (priority_queue_multi_p (head))
161 {
162 struct cbtype cb = { type, check_deps };
163 prio_splay_tree_foreach (&head->t,
164 priority_tree_verify_callback, &cb);
165 }
166 else
167 priority_list_verify (type, &head->l, check_deps);
168 }
169 #endif /* _LIBGOMP_CHECKING_ */
170
171 /* Tree version of priority_queue_find. */
172
173 static struct gomp_task *
174 priority_tree_find (enum priority_queue_type type,
175 prio_splay_tree_node node,
176 priority_queue_predicate pred)
177 {
178 again:
179 if (!node)
180 return NULL;
181 struct gomp_task *task = priority_tree_find (type, node->right, pred);
182 if (task)
183 return task;
184 task = priority_node_to_task (type, node->key.l.tasks);
185 if (pred (task))
186 return task;
187 node = node->left;
188 goto again;
189 }
190
191 /* List version of priority_queue_find. */
192
193 static struct gomp_task *
194 priority_list_find (enum priority_queue_type type,
195 struct priority_list *list,
196 priority_queue_predicate pred)
197 {
198 struct priority_node *node = list->tasks;
199 if (!node)
200 return NULL;
201
202 do
203 {
204 struct gomp_task *task = priority_node_to_task (type, node);
205 if (pred (task))
206 return task;
207 node = node->next;
208 }
209 while (node != list->tasks);
210
211 return NULL;
212 }
213
214 /* Return the highest priority task in the priority queue HEAD that
215 satisfies the predicate PRED. HEAD contains tasks of type TYPE. */
216
217 struct gomp_task *
218 priority_queue_find (enum priority_queue_type type,
219 struct priority_queue *head,
220 priority_queue_predicate pred)
221 {
222 if (priority_queue_multi_p (head))
223 return priority_tree_find (type, head->t.root, pred);
224 else
225 return priority_list_find (type, &head->l, pred);
226 }
227
228 /* Remove NODE from priority queue HEAD, wherever it may be inside the
229 tree. HEAD contains tasks of type TYPE. */
230
231 void
232 priority_tree_remove (enum priority_queue_type type,
233 struct priority_queue *head,
234 struct priority_node *node)
235 {
236 /* ?? The only reason this function is not inlined is because we
237 need to find the priority within gomp_task (which has not been
238 completely defined in the header file). If the lack of inlining
239 is a concern, we could pass the priority number as a
240 parameter, or we could move this to libgomp.h. */
241 int priority = priority_node_to_task (type, node)->priority;
242
243 /* ?? We could avoid this lookup by keeping a pointer to the key in
244 the priority_node. */
245 struct priority_list *list
246 = priority_queue_lookup_priority (head, priority);
247 #if _LIBGOMP_CHECKING_
248 if (!list)
249 gomp_fatal ("Unable to find priority %d", priority);
250 #endif
251 /* If NODE was the last in its priority, clean up the priority. */
252 if (priority_list_remove (list, node, MEMMODEL_RELAXED))
253 {
254 prio_splay_tree_remove (&head->t, (prio_splay_tree_key) list);
255 list->tasks = NULL;
256 #if _LIBGOMP_CHECKING_
257 memset (list, 0xaf, sizeof (*list));
258 #endif
259 free (list);
260 }
261 }
262
263 /* Return the highest priority WAITING task in a splay tree NODE. If
264 there are no WAITING tasks available, return NULL.
265
266 NODE is a priority list containing tasks of type TYPE.
267
268 The right most node in a tree contains the highest priority.
269 Recurse down to find such a node. If the task at that max node is
270 not WAITING, bubble back up and look at the remaining tasks
271 in-order. */
272
273 static struct gomp_task *
274 priority_tree_next_task_1 (enum priority_queue_type type,
275 prio_splay_tree_node node)
276 {
277 again:
278 if (!node)
279 return NULL;
280 struct gomp_task *ret = priority_tree_next_task_1 (type, node->right);
281 if (ret)
282 return ret;
283 ret = priority_node_to_task (type, node->key.l.tasks);
284 if (ret->kind == GOMP_TASK_WAITING)
285 return ret;
286 node = node->left;
287 goto again;
288 }
289
290 /* Return the highest priority WAITING task from within Q1 and Q2,
291 while giving preference to tasks from Q1. Q1 is a queue containing
292 items of type TYPE1. Q2 is a queue containing items of type TYPE2.
293
294 Since we are mostly interested in Q1, if there are no WAITING tasks
295 in Q1, we don't bother checking Q2, and just return NULL.
296
297 As a special case, Q2 can be NULL, in which case, we just choose
298 the highest priority WAITING task in Q1. This is an optimization
299 to speed up looking through only one queue.
300
301 If the returned task is chosen from Q1, *Q1_CHOSEN_P is set to
302 TRUE, otherwise it is set to FALSE. */
303
304 struct gomp_task *
305 priority_tree_next_task (enum priority_queue_type type1,
306 struct priority_queue *q1,
307 enum priority_queue_type type2,
308 struct priority_queue *q2,
309 bool *q1_chosen_p)
310 {
311 struct gomp_task *t1 = priority_tree_next_task_1 (type1, q1->t.root);
312 if (!t1
313 /* Special optimization when only searching through one queue. */
314 || !q2)
315 {
316 *q1_chosen_p = true;
317 return t1;
318 }
319 struct gomp_task *t2 = priority_tree_next_task_1 (type2, q2->t.root);
320 if (!t2 || t1->priority > t2->priority)
321 {
322 *q1_chosen_p = true;
323 return t1;
324 }
325 if (t2->priority > t1->priority)
326 {
327 *q1_chosen_p = false;
328 return t2;
329 }
330 /* If we get here, the priorities are the same, so we must look at
331 parent_depends_on to make our decision. */
332 #if _LIBGOMP_CHECKING_
333 if (t1 != t2)
334 gomp_fatal ("priority_tree_next_task: t1 != t2");
335 #endif
336 if (t2->parent_depends_on && !t1->parent_depends_on)
337 {
338 *q1_chosen_p = false;
339 return t2;
340 }
341 *q1_chosen_p = true;
342 return t1;
343 }
344
345 /* Priority splay trees comparison function. */
346 static inline int
347 prio_splay_compare (prio_splay_tree_key x, prio_splay_tree_key y)
348 {
349 if (x->l.priority == y->l.priority)
350 return 0;
351 return x->l.priority < y->l.priority ? -1 : 1;
352 }
353
354 /* Define another splay tree instantiation, for priority_list's. */
355 #define splay_tree_prefix prio
356 #define splay_tree_c
357 #include "splay-tree.h"