src/lib/object.h

   1 #ifndef BABELTRACE_OBJECT_INTERNAL_H
   2 #define BABELTRACE_OBJECT_INTERNAL_H
   3
   4 /*
   5  * Copyright 2017-2018 Philippe Proulx <pproulx@efficios.com>
   6  * Copyright 2015 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   7  *
   8  * Permission is hereby granted, free of charge, to any person obtaining a copy
   9  * of this software and associated documentation files (the "Software"), to deal
  10  * in the Software without restriction, including without limitation the rights
  11  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  12  * copies of the Software, and to permit persons to whom the Software is
  13  * furnished to do so, subject to the following conditions:
  14  *
  15  * The above copyright notice and this permission notice shall be included in
  16  * all copies or substantial portions of the Software.
  17  *
  18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  19  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  21  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  22  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  23  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  24  * SOFTWARE.
  25  */
  26
  27 #include "common/macros.h"
  28 #include "common/assert.h"
  29 #include <stdbool.h>
  30
  31 /*
  32  * Some parts of the Babeltrace project use this internal library header
  33  * for internal reference counting. Until we make this header generic
  34  * for the whole project, make it possible to disable logging in this
  35  * file by defining `BT_OBJECT_DONT_LOG` because it's possible that the
  36  * BT_LOGT() statements here won't find the log level
  37  * (`BT_LOG_OUTPUT_LEVEL`).
  38  */
  39 #if defined(BT_LOGT) && !defined(BT_OBJECT_DONT_LOG)
  40 # define _BT_OBJECT_LOGGING_ENABLED
  41 #endif
  42
  43 struct bt_object;
  44
  45 typedef void (*bt_object_release_func)(struct bt_object *);
  46 typedef void (*bt_object_parent_is_owner_listener_func)(
  47                 struct bt_object *);
  48
  49 static inline
  50 void bt_object_get_no_null_check(const void *obj);
  51
  52 static inline
  53 void bt_object_put_no_null_check(const void *obj);
  54
  55 /*
  56  * Babeltrace object base.
  57  *
  58  * All objects publicly exposed by Babeltrace APIs must contain this
  59  * object as their first member.
  60  */
  61 struct bt_object {
  62         /*
  63          * True if this object is shared, that is, it has a reference
  64          * count.
  65          */
  66         bool is_shared;
  67
  68         /*
  69          * Current reference count.
  70          */
  71         unsigned long long ref_count;
  72
  73         /*
  74          * Release function called when the object's reference count
  75          * falls to zero. For an object with a parent, this function is
  76          * bt_object_with_parent_release_func(), which calls
  77          * `spec_release_func` below if there's no current parent.
  78          */
  79         bt_object_release_func release_func;
  80
  81         /*
  82          * Specific release function called by
  83          * bt_object_with_parent_release_func() or directly by a
  84          * parent object.
  85          */
  86         bt_object_release_func spec_release_func;
  87
  88         /*
  89          * Optional callback for an object with a parent, called by
  90          * bt_object_with_parent_release_func() to indicate to the
  91          * object that its parent is its owner.
  92          */
  93         bt_object_parent_is_owner_listener_func
  94                 parent_is_owner_listener_func;
  95
  96         /*
  97          * Optional parent object.
  98          */
  99         struct bt_object *parent;
 100 };
 101
 102 static inline
 103 unsigned long long bt_object_get_ref_count(const struct bt_object *c_obj)
 104 {
 105         struct bt_object *obj = (void *) c_obj;
 106
 107         BT_ASSERT(obj);
 108         BT_ASSERT(obj->is_shared);
 109         return obj->ref_count;
 110 }
 111
 112 static inline
 113 struct bt_object *bt_object_borrow_parent(const struct bt_object *c_obj)
 114 {
 115         struct bt_object *obj = (void *) c_obj;
 116
 117         BT_ASSERT(obj);
 118         BT_ASSERT(obj->is_shared);
 119         return obj->parent;
 120 }
 121
 122 static inline
 123 struct bt_object *bt_object_get_parent(const struct bt_object *c_obj)
 124 {
 125         struct bt_object *obj = (void *) c_obj;
 126         struct bt_object *parent = bt_object_borrow_parent(obj);
 127
 128         if (parent) {
 129                 bt_object_get_no_null_check(parent);
 130         }
 131
 132         return parent;
 133 }
 134
 135 static inline
 136 void bt_object_set_parent(struct bt_object *child, struct bt_object *parent)
 137 {
 138         BT_ASSERT(child);
 139         BT_ASSERT(child->is_shared);
 140
 141 #ifdef _BT_OBJECT_LOGGING_ENABLED
 142         BT_LOGT("Setting object's parent: addr=%p, parent-addr=%p",
 143                 child, parent);
 144 #endif
 145
 146         /*
 147          * It is assumed that a "child" having a parent is publicly
 148          * reachable. Therefore, a reference to its parent must be
 149          * taken. The reference to the parent will be released once the
 150          * object's reference count falls to zero.
 151          */
 152         if (parent) {
 153                 BT_ASSERT(!child->parent);
 154                 child->parent = parent;
 155                 bt_object_get_no_null_check(parent);
 156         } else {
 157                 if (child->parent) {
 158                         bt_object_put_no_null_check(child->parent);
 159                 }
 160
 161                 child->parent = NULL;
 162         }
 163 }
 164
 165 static inline
 166 void bt_object_try_spec_release(struct bt_object *obj)
 167 {
 168         BT_ASSERT(obj);
 169         BT_ASSERT(obj->is_shared);
 170         BT_ASSERT(obj->spec_release_func);
 171
 172         if (bt_object_get_ref_count(obj) == 0) {
 173                 obj->spec_release_func(obj);
 174         }
 175 }
 176
 177 static inline
 178 void bt_object_with_parent_release_func(struct bt_object *obj)
 179 {
 180         if (obj->parent) {
 181                 /*
 182                  * Keep our own copy of the parent address because `obj`
 183                  * could be destroyed in
 184                  * obj->parent_is_owner_listener_func().
 185                  */
 186                 struct bt_object *parent = obj->parent;
 187
 188 #ifdef _BT_OBJECT_LOGGING_ENABLED
 189                 BT_LOGT("Releasing parented object: addr=%p, ref-count=%llu, "
 190                         "parent-addr=%p, parent-ref-count=%llu",
 191                         obj, obj->ref_count,
 192                         parent, parent->ref_count);
 193 #endif
 194
 195                 if (obj->parent_is_owner_listener_func) {
 196                         /*
 197                          * Object has a chance to destroy itself here
 198                          * under certain conditions and notify its
 199                          * parent. At this point the parent is
 200                          * guaranteed to exist because it's not put yet.
 201                          */
 202                         obj->parent_is_owner_listener_func(obj);
 203                 }
 204
 205                 /* The release function will be invoked by the parent. */
 206                 bt_object_put_no_null_check(parent);
 207         } else {
 208                 bt_object_try_spec_release(obj);
 209         }
 210 }
 211
 212 static inline
 213 void bt_object_init(struct bt_object *obj, bool is_shared,
 214                 bt_object_release_func release_func)
 215 {
 216         BT_ASSERT(obj);
 217         BT_ASSERT(!is_shared || release_func);
 218         obj->is_shared = is_shared;
 219         obj->release_func = release_func;
 220         obj->parent_is_owner_listener_func = NULL;
 221         obj->spec_release_func = NULL;
 222         obj->parent = NULL;
 223         obj->ref_count = 1;
 224 }
 225
 226 static inline
 227 void bt_object_init_shared(struct bt_object *obj,
 228                 bt_object_release_func release_func)
 229 {
 230         bt_object_init(obj, true, release_func);
 231 }
 232
 233 static inline
 234 void bt_object_init_unique(struct bt_object *obj)
 235 {
 236         bt_object_init(obj, false, NULL);
 237 }
 238
 239 static inline
 240 void bt_object_init_shared_with_parent(struct bt_object *obj,
 241                 bt_object_release_func spec_release_func)
 242 {
 243         BT_ASSERT(obj);
 244         BT_ASSERT(spec_release_func);
 245         bt_object_init_shared(obj, bt_object_with_parent_release_func);
 246         obj->spec_release_func = spec_release_func;
 247 }
 248
 249 static inline
 250 void bt_object_set_parent_is_owner_listener_func(struct bt_object *obj,
 251                 bt_object_parent_is_owner_listener_func func)
 252 {
 253         BT_ASSERT(obj);
 254         BT_ASSERT(obj->is_shared);
 255         BT_ASSERT(obj->spec_release_func);
 256         ((struct bt_object *) obj)->parent_is_owner_listener_func = func;
 257 }
 258
 259 static inline
 260 void bt_object_inc_ref_count(const struct bt_object *c_obj)
 261 {
 262         struct bt_object *obj = (void *) c_obj;
 263
 264         BT_ASSERT(obj);
 265         BT_ASSERT(obj->is_shared);
 266         obj->ref_count++;
 267         BT_ASSERT(obj->ref_count != 0);
 268 }
 269
 270 static inline
 271 void bt_object_get_no_null_check_no_parent_check(const struct bt_object *c_obj)
 272 {
 273         struct bt_object *obj = (void *) c_obj;
 274
 275         BT_ASSERT(obj);
 276         BT_ASSERT(obj->is_shared);
 277
 278 #ifdef _BT_OBJECT_LOGGING_ENABLED
 279         BT_LOGT("Incrementing object's reference count: %llu -> %llu: "
 280                 "addr=%p, cur-count=%llu, new-count=%llu",
 281                 obj->ref_count, obj->ref_count + 1,
 282                 obj, obj->ref_count, obj->ref_count + 1);
 283 #endif
 284
 285         bt_object_inc_ref_count(obj);
 286 }
 287
 288 static inline
 289 void bt_object_get_no_null_check(const void *c_obj)
 290 {
 291         struct bt_object *obj = (void *) c_obj;
 292
 293         BT_ASSERT(obj);
 294         BT_ASSERT(obj->is_shared);
 295
 296         if (G_UNLIKELY(obj->parent && bt_object_get_ref_count(obj) == 0)) {
 297 #ifdef _BT_OBJECT_LOGGING_ENABLED
 298                 BT_LOGT("Incrementing object's parent's reference count: "
 299                         "addr=%p, parent-addr=%p", obj, obj->parent);
 300 #endif
 301
 302                 bt_object_get_no_null_check(obj->parent);
 303         }
 304
 305 #ifdef _BT_OBJECT_LOGGING_ENABLED
 306         BT_LOGT("Incrementing object's reference count: %llu -> %llu: "
 307                 "addr=%p, cur-count=%llu, new-count=%llu",
 308                 obj->ref_count, obj->ref_count + 1,
 309                 obj, obj->ref_count, obj->ref_count + 1);
 310 #endif
 311
 312         bt_object_inc_ref_count(obj);
 313 }
 314
 315 static inline
 316 void bt_object_put_no_null_check(const void *c_obj)
 317 {
 318         struct bt_object *obj = (void *) c_obj;
 319
 320         BT_ASSERT(obj);
 321         BT_ASSERT(obj->is_shared);
 322         BT_ASSERT(obj->ref_count > 0);
 323
 324 #ifdef _BT_OBJECT_LOGGING_ENABLED
 325         BT_LOGT("Decrementing object's reference count: %llu -> %llu: "
 326                 "addr=%p, cur-count=%llu, new-count=%llu",
 327                 obj->ref_count, obj->ref_count - 1,
 328                 obj, obj->ref_count, obj->ref_count - 1);
 329 #endif
 330
 331         obj->ref_count--;
 332
 333         if (obj->ref_count == 0) {
 334                 BT_ASSERT(obj->release_func);
 335                 obj->release_func(obj);
 336         }
 337 }
 338
 339 static inline
 340 void bt_object_get_ref(const void *ptr)
 341 {
 342         struct bt_object *obj = (void *) ptr;
 343
 344         if (G_UNLIKELY(!obj)) {
 345                 return;
 346         }
 347
 348 #ifdef BT_ASSERT_PRE
 349         BT_ASSERT_PRE(obj->is_shared, "Object is not shared: %!+O", obj);
 350 #endif
 351
 352         bt_object_get_no_null_check(obj);
 353 }
 354
 355 static inline
 356 void bt_object_put_ref(const void *ptr)
 357 {
 358         struct bt_object *obj = (void *) ptr;
 359
 360         if (G_UNLIKELY(!obj)) {
 361                 return;
 362         }
 363
 364 #ifdef BT_ASSERT_PRE
 365         BT_ASSERT_PRE(obj->is_shared, "Object is not shared: %!+O", obj);
 366         BT_ASSERT_PRE(bt_object_get_ref_count(obj) > 0,
 367                 "Decrementing a reference count set to 0: %!+O", ptr);
 368 #endif
 369
 370         bt_object_put_no_null_check(obj);
 371 }
 372
 373 #define BT_OBJECT_PUT_REF_AND_RESET(_var)       \
 374         do {                                    \
 375                 bt_object_put_ref(_var);        \
 376                 (_var) = NULL;                  \
 377         } while (0)
 378
 379 #define BT_OBJECT_MOVE_REF(_var_dst, _var_src)  \
 380         do {                                    \
 381                 bt_object_put_ref(_var_dst);    \
 382                 (_var_dst) = (_var_src);        \
 383                 (_var_src) = NULL;              \
 384         } while (0)
 385
 386 #endif /* BABELTRACE_OBJECT_INTERNAL_H */