libgomp/priority_queue.c

   1 /* Copyright (C) 2015-2019 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 /* Remove NODE from priority queue HEAD, wherever it may be inside the
 172    tree.  HEAD contains tasks of type TYPE.  */
 173
 174 void
 175 priority_tree_remove (enum priority_queue_type type,
 176                       struct priority_queue *head,
 177                       struct priority_node *node)
 178 {
 179   /* ?? The only reason this function is not inlined is because we
 180      need to find the priority within gomp_task (which has not been
 181      completely defined in the header file).  If the lack of inlining
 182      is a concern, we could pass the priority number as a
 183      parameter, or we could move this to libgomp.h.  */
 184   int priority = priority_node_to_task (type, node)->priority;
 185
 186   /* ?? We could avoid this lookup by keeping a pointer to the key in
 187      the priority_node.  */
 188   struct priority_list *list
 189     = priority_queue_lookup_priority (head, priority);
 190 #if _LIBGOMP_CHECKING_
 191   if (!list)
 192     gomp_fatal ("Unable to find priority %d", priority);
 193 #endif
 194   /* If NODE was the last in its priority, clean up the priority.  */
 195   if (priority_list_remove (list, node, MEMMODEL_RELAXED))
 196     {
 197       prio_splay_tree_remove (&head->t, (prio_splay_tree_key) list);
 198       list->tasks = NULL;
 199 #if _LIBGOMP_CHECKING_
 200       memset (list, 0xaf, sizeof (*list));
 201 #endif
 202       free (list);
 203     }
 204 }
 205
 206 /* Return the highest priority WAITING task in a splay tree NODE.  If
 207    there are no WAITING tasks available, return NULL.
 208
 209    NODE is a priority list containing tasks of type TYPE.
 210
 211    The right most node in a tree contains the highest priority.
 212    Recurse down to find such a node.  If the task at that max node is
 213    not WAITING, bubble back up and look at the remaining tasks
 214    in-order.  */
 215
 216 static struct gomp_task *
 217 priority_tree_next_task_1 (enum priority_queue_type type,
 218                            prio_splay_tree_node node)
 219 {
 220  again:
 221   if (!node)
 222     return NULL;
 223   struct gomp_task *ret = priority_tree_next_task_1 (type, node->right);
 224   if (ret)
 225     return ret;
 226   ret = priority_node_to_task (type, node->key.l.tasks);
 227   if (ret->kind == GOMP_TASK_WAITING)
 228     return ret;
 229   node = node->left;
 230   goto again;
 231 }
 232
 233 /* Return the highest priority WAITING task from within Q1 and Q2,
 234    while giving preference to tasks from Q1.  Q1 is a queue containing
 235    items of type TYPE1.  Q2 is a queue containing items of type TYPE2.
 236
 237    Since we are mostly interested in Q1, if there are no WAITING tasks
 238    in Q1, we don't bother checking Q2, and just return NULL.
 239
 240    As a special case, Q2 can be NULL, in which case, we just choose
 241    the highest priority WAITING task in Q1.  This is an optimization
 242    to speed up looking through only one queue.
 243
 244    If the returned task is chosen from Q1, *Q1_CHOSEN_P is set to
 245    TRUE, otherwise it is set to FALSE.  */
 246
 247 struct gomp_task *
 248 priority_tree_next_task (enum priority_queue_type type1,
 249                          struct priority_queue *q1,
 250                          enum priority_queue_type type2,
 251                          struct priority_queue *q2,
 252                          bool *q1_chosen_p)
 253 {
 254   struct gomp_task *t1 = priority_tree_next_task_1 (type1, q1->t.root);
 255   if (!t1
 256       /* Special optimization when only searching through one queue.  */
 257       || !q2)
 258     {
 259       *q1_chosen_p = true;
 260       return t1;
 261     }
 262   struct gomp_task *t2 = priority_tree_next_task_1 (type2, q2->t.root);
 263   if (!t2 || t1->priority > t2->priority)
 264     {
 265       *q1_chosen_p = true;
 266       return t1;
 267     }
 268   if (t2->priority > t1->priority)
 269     {
 270       *q1_chosen_p = false;
 271       return t2;
 272     }
 273   /* If we get here, the priorities are the same, so we must look at
 274      parent_depends_on to make our decision.  */
 275 #if _LIBGOMP_CHECKING_
 276   if (t1 != t2)
 277     gomp_fatal ("priority_tree_next_task: t1 != t2");
 278 #endif
 279   if (t2->parent_depends_on && !t1->parent_depends_on)
 280     {
 281       *q1_chosen_p = false;
 282       return t2;
 283     }
 284   *q1_chosen_p = true;
 285   return t1;
 286 }
 287
 288 /* Priority splay trees comparison function.  */
 289 static inline int
 290 prio_splay_compare (prio_splay_tree_key x, prio_splay_tree_key y)
 291 {
 292   if (x->l.priority == y->l.priority)
 293     return 0;
 294   return x->l.priority < y->l.priority ? -1 : 1;
 295 }
 296
 297 /* Define another splay tree instantiation, for priority_list's.  */
 298 #define splay_tree_prefix prio
 299 #define splay_tree_c
 300 #include "splay-tree.h"