src/queue_internal.h

   1 /*
   2  * Copyright (c) 2008-2013 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_APACHE_LICENSE_HEADER_START@
   5  *
   6  * Licensed under the Apache License, Version 2.0 (the "License");
   7  * you may not use this file except in compliance with the License.
   8  * You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  *
  18  * @APPLE_APACHE_LICENSE_HEADER_END@
  19  */
  20
  21 /*
  22  * IMPORTANT: This header file describes INTERNAL interfaces to libdispatch
  23  * which are subject to change in future releases of Mac OS X. Any applications
  24  * relying on these interfaces WILL break.
  25  */
  26
  27 #ifndef __DISPATCH_QUEUE_INTERNAL__
  28 #define __DISPATCH_QUEUE_INTERNAL__
  29
  30 #ifndef __DISPATCH_INDIRECT__
  31 #error "Please #include <dispatch/dispatch.h> instead of this file directly."
  32 #include <dispatch/base.h> // for HeaderDoc
  33 #endif
  34
  35 #if defined(__BLOCKS__) && !defined(DISPATCH_ENABLE_PTHREAD_ROOT_QUEUES)
  36 #define DISPATCH_ENABLE_PTHREAD_ROOT_QUEUES 1 // <rdar://problem/10719357>
  37 #endif
  38
  39 /* x86 & cortex-a8 have a 64 byte cacheline */
  40 #define DISPATCH_CACHELINE_SIZE 64u
  41 #define DISPATCH_CONTINUATION_SIZE DISPATCH_CACHELINE_SIZE
  42 #define ROUND_UP_TO_CACHELINE_SIZE(x) \
  43                 (((x) + (DISPATCH_CACHELINE_SIZE - 1u)) & \
  44                 ~(DISPATCH_CACHELINE_SIZE - 1u))
  45 #define ROUND_UP_TO_CONTINUATION_SIZE(x) \
  46                 (((x) + (DISPATCH_CONTINUATION_SIZE - 1u)) & \
  47                 ~(DISPATCH_CONTINUATION_SIZE - 1u))
  48 #define ROUND_UP_TO_VECTOR_SIZE(x) \
  49                 (((x) + 15u) & ~15u)
  50 #define DISPATCH_CACHELINE_ALIGN \
  51                 __attribute__((__aligned__(DISPATCH_CACHELINE_SIZE)))
  52
  53
  54 #define DISPATCH_QUEUE_CACHELINE_PADDING \
  55                 char _dq_pad[DISPATCH_QUEUE_CACHELINE_PAD]
  56 #ifdef __LP64__
  57 #define DISPATCH_QUEUE_CACHELINE_PAD (( \
  58                 (3*sizeof(void*) - DISPATCH_INTROSPECTION_QUEUE_LIST_SIZE) \
  59                 + DISPATCH_CACHELINE_SIZE) % DISPATCH_CACHELINE_SIZE)
  60 #else
  61 #define DISPATCH_QUEUE_CACHELINE_PAD (( \
  62                 (0*sizeof(void*) - DISPATCH_INTROSPECTION_QUEUE_LIST_SIZE) \
  63                 + DISPATCH_CACHELINE_SIZE) % DISPATCH_CACHELINE_SIZE)
  64 #if !DISPATCH_INTROSPECTION
  65 // No padding, DISPATCH_QUEUE_CACHELINE_PAD == 0
  66 #undef DISPATCH_QUEUE_CACHELINE_PADDING
  67 #define DISPATCH_QUEUE_CACHELINE_PADDING
  68 #endif
  69 #endif
  70
  71 // If dc_vtable is less than 127, then the object is a continuation.
  72 // Otherwise, the object has a private layout and memory management rules. The
  73 // layout until after 'do_next' must align with normal objects.
  74 #define DISPATCH_CONTINUATION_HEADER(x) \
  75         _OS_OBJECT_HEADER( \
  76         const void *do_vtable, \
  77         do_ref_cnt, \
  78         do_xref_cnt); \
  79         struct dispatch_##x##_s *volatile do_next; \
  80         dispatch_function_t dc_func; \
  81         void *dc_ctxt; \
  82         void *dc_data; \
  83         void *dc_other;
  84
  85 #define DISPATCH_OBJ_ASYNC_BIT          0x1
  86 #define DISPATCH_OBJ_BARRIER_BIT        0x2
  87 #define DISPATCH_OBJ_GROUP_BIT          0x4
  88 #define DISPATCH_OBJ_SYNC_SLOW_BIT      0x8
  89 // vtables are pointers far away from the low page in memory
  90 #define DISPATCH_OBJ_IS_VTABLE(x) ((unsigned long)(x)->do_vtable > 127ul)
  91
  92 struct dispatch_continuation_s {
  93         DISPATCH_CONTINUATION_HEADER(continuation);
  94 };
  95
  96 typedef struct dispatch_continuation_s *dispatch_continuation_t;
  97
  98 struct dispatch_apply_s {
  99         size_t volatile da_index, da_todo;
 100         size_t da_iterations, da_nested;
 101         dispatch_continuation_t da_dc;
 102         _dispatch_thread_semaphore_t da_sema;
 103         uint32_t da_thr_cnt;
 104 };
 105
 106 typedef struct dispatch_apply_s *dispatch_apply_t;
 107
 108 DISPATCH_CLASS_DECL(queue_attr);
 109 struct dispatch_queue_attr_s {
 110         DISPATCH_STRUCT_HEADER(queue_attr);
 111 };
 112
 113 #define DISPATCH_QUEUE_HEADER \
 114         uint32_t volatile dq_running; \
 115         struct dispatch_object_s *volatile dq_items_head; \
 116         /* LP64 global queue cacheline boundary */ \
 117         struct dispatch_object_s *volatile dq_items_tail; \
 118         dispatch_queue_t dq_specific_q; \
 119         uint32_t dq_width; \
 120         unsigned int dq_is_thread_bound:1; \
 121         unsigned long dq_serialnum; \
 122         const char *dq_label; \
 123         DISPATCH_INTROSPECTION_QUEUE_LIST;
 124
 125 DISPATCH_CLASS_DECL(queue);
 126 struct dispatch_queue_s {
 127         DISPATCH_STRUCT_HEADER(queue);
 128         DISPATCH_QUEUE_HEADER;
 129         DISPATCH_QUEUE_CACHELINE_PADDING; // for static queues only
 130 };
 131
 132 DISPATCH_INTERNAL_SUBCLASS_DECL(queue_root, queue);
 133 DISPATCH_INTERNAL_SUBCLASS_DECL(queue_runloop, queue);
 134 DISPATCH_INTERNAL_SUBCLASS_DECL(queue_mgr, queue);
 135
 136 DISPATCH_DECL_INTERNAL_SUBCLASS(dispatch_queue_specific_queue, dispatch_queue);
 137 DISPATCH_CLASS_DECL(queue_specific_queue);
 138
 139 extern struct dispatch_queue_s _dispatch_mgr_q;
 140
 141 void _dispatch_queue_destroy(dispatch_object_t dou);
 142 void _dispatch_queue_dispose(dispatch_queue_t dq);
 143 void _dispatch_queue_invoke(dispatch_queue_t dq);
 144 void _dispatch_queue_push_list_slow(dispatch_queue_t dq,
 145                 struct dispatch_object_s *obj, unsigned int n);
 146 void _dispatch_queue_push_slow(dispatch_queue_t dq,
 147                 struct dispatch_object_s *obj);
 148 unsigned long _dispatch_queue_probe(dispatch_queue_t dq);
 149 dispatch_queue_t _dispatch_wakeup(dispatch_object_t dou);
 150 _dispatch_thread_semaphore_t _dispatch_queue_drain(dispatch_object_t dou);
 151 void _dispatch_queue_specific_queue_dispose(dispatch_queue_specific_queue_t
 152                 dqsq);
 153 unsigned long _dispatch_root_queue_probe(dispatch_queue_t dq);
 154 void _dispatch_pthread_root_queue_dispose(dispatch_queue_t dq);
 155 unsigned long _dispatch_runloop_queue_probe(dispatch_queue_t dq);
 156 void _dispatch_runloop_queue_xref_dispose(dispatch_queue_t dq);
 157 void _dispatch_runloop_queue_dispose(dispatch_queue_t dq);
 158 void _dispatch_mgr_queue_drain(void);
 159 unsigned long _dispatch_mgr_queue_probe(dispatch_queue_t dq);
 160 #if DISPATCH_ENABLE_PTHREAD_ROOT_QUEUES
 161 void _dispatch_mgr_priority_init(void);
 162 #else
 163 static inline void _dispatch_mgr_priority_init(void) {}
 164 #endif
 165 void _dispatch_after_timer_callback(void *ctxt);
 166 void _dispatch_async_redirect_invoke(void *ctxt);
 167 void _dispatch_sync_recurse_invoke(void *ctxt);
 168 void _dispatch_apply_invoke(void *ctxt);
 169 void _dispatch_apply_redirect_invoke(void *ctxt);
 170 void _dispatch_barrier_trysync_f(dispatch_queue_t dq, void *ctxt,
 171                 dispatch_function_t func);
 172
 173 #if DISPATCH_DEBUG
 174 void dispatch_debug_queue(dispatch_queue_t dq, const char* str);
 175 #else
 176 static inline void dispatch_debug_queue(dispatch_queue_t dq DISPATCH_UNUSED,
 177                 const char* str DISPATCH_UNUSED) {}
 178 #endif
 179
 180 size_t dispatch_queue_debug(dispatch_queue_t dq, char* buf, size_t bufsiz);
 181 size_t _dispatch_queue_debug_attr(dispatch_queue_t dq, char* buf,
 182                 size_t bufsiz);
 183
 184 #define DISPATCH_QUEUE_PRIORITY_COUNT 4
 185 #define DISPATCH_ROOT_QUEUE_COUNT (DISPATCH_QUEUE_PRIORITY_COUNT * 2)
 186
 187 // overcommit priority index values need bit 1 set
 188 enum {
 189         DISPATCH_ROOT_QUEUE_IDX_LOW_PRIORITY = 0,
 190         DISPATCH_ROOT_QUEUE_IDX_LOW_OVERCOMMIT_PRIORITY,
 191         DISPATCH_ROOT_QUEUE_IDX_DEFAULT_PRIORITY,
 192         DISPATCH_ROOT_QUEUE_IDX_DEFAULT_OVERCOMMIT_PRIORITY,
 193         DISPATCH_ROOT_QUEUE_IDX_HIGH_PRIORITY,
 194         DISPATCH_ROOT_QUEUE_IDX_HIGH_OVERCOMMIT_PRIORITY,
 195         DISPATCH_ROOT_QUEUE_IDX_BACKGROUND_PRIORITY,
 196         DISPATCH_ROOT_QUEUE_IDX_BACKGROUND_OVERCOMMIT_PRIORITY,
 197 };
 198
 199 extern unsigned long volatile _dispatch_queue_serial_numbers;
 200 extern struct dispatch_queue_s _dispatch_root_queues[];
 201
 202 #if !(USE_OBJC && __OBJC2__)
 203
 204 DISPATCH_ALWAYS_INLINE
 205 static inline bool
 206 _dispatch_queue_push_list2(dispatch_queue_t dq, struct dispatch_object_s *head,
 207                 struct dispatch_object_s *tail)
 208 {
 209         struct dispatch_object_s *prev;
 210         tail->do_next = NULL;
 211         prev = dispatch_atomic_xchg2o(dq, dq_items_tail, tail, release);
 212         if (fastpath(prev)) {
 213                 // if we crash here with a value less than 0x1000, then we are at a
 214                 // known bug in client code for example, see _dispatch_queue_dispose
 215                 // or _dispatch_atfork_child
 216                 prev->do_next = head;
 217         }
 218         return (prev != NULL);
 219 }
 220
 221 DISPATCH_ALWAYS_INLINE
 222 static inline void
 223 _dispatch_queue_push_list(dispatch_queue_t dq, dispatch_object_t _head,
 224                 dispatch_object_t _tail, unsigned int n)
 225 {
 226         struct dispatch_object_s *head = _head._do, *tail = _tail._do;
 227         if (!fastpath(_dispatch_queue_push_list2(dq, head, tail))) {
 228                 _dispatch_queue_push_list_slow(dq, head, n);
 229         }
 230 }
 231
 232 DISPATCH_ALWAYS_INLINE
 233 static inline void
 234 _dispatch_queue_push(dispatch_queue_t dq, dispatch_object_t _tail)
 235 {
 236         struct dispatch_object_s *tail = _tail._do;
 237         if (!fastpath(_dispatch_queue_push_list2(dq, tail, tail))) {
 238                 _dispatch_queue_push_slow(dq, tail);
 239         }
 240 }
 241
 242 DISPATCH_ALWAYS_INLINE
 243 static inline void
 244 _dispatch_queue_push_wakeup(dispatch_queue_t dq, dispatch_object_t _tail,
 245                 bool wakeup)
 246 {
 247         struct dispatch_object_s *tail = _tail._do;
 248         if (!fastpath(_dispatch_queue_push_list2(dq, tail, tail))) {
 249                 _dispatch_queue_push_slow(dq, tail);
 250         } else if (slowpath(wakeup)) {
 251                 _dispatch_wakeup(dq);
 252         }
 253 }
 254
 255 DISPATCH_ALWAYS_INLINE
 256 static inline void
 257 _dispatch_queue_class_invoke(dispatch_object_t dou,
 258                 dispatch_queue_t (*invoke)(dispatch_object_t,
 259                 _dispatch_thread_semaphore_t*))
 260 {
 261         dispatch_queue_t dq = dou._dq;
 262         if (!slowpath(DISPATCH_OBJECT_SUSPENDED(dq)) &&
 263                         fastpath(dispatch_atomic_cmpxchg2o(dq, dq_running, 0, 1, acquire))){
 264                 dispatch_queue_t tq = NULL;
 265                 _dispatch_thread_semaphore_t sema = 0;
 266                 tq = invoke(dq, &sema);
 267                 // We do not need to check the result.
 268                 // When the suspend-count lock is dropped, then the check will happen.
 269                 (void)dispatch_atomic_dec2o(dq, dq_running, release);
 270                 if (sema) {
 271                         _dispatch_thread_semaphore_signal(sema);
 272                 } else if (tq) {
 273                         return _dispatch_queue_push(tq, dq);
 274                 }
 275         }
 276         dq->do_next = DISPATCH_OBJECT_LISTLESS;
 277         if (!dispatch_atomic_sub2o(dq, do_suspend_cnt,
 278                         DISPATCH_OBJECT_SUSPEND_LOCK, release)) {
 279                 dispatch_atomic_barrier(seq_cst); // <rdar://problem/11915417>
 280                 if (dispatch_atomic_load2o(dq, dq_running, seq_cst) == 0) {
 281                         _dispatch_wakeup(dq); // verify that the queue is idle
 282                 }
 283         }
 284         _dispatch_release(dq); // added when the queue is put on the list
 285 }
 286
 287 DISPATCH_ALWAYS_INLINE
 288 static inline dispatch_queue_t
 289 _dispatch_queue_get_current(void)
 290 {
 291         return (dispatch_queue_t)_dispatch_thread_getspecific(dispatch_queue_key);
 292 }
 293
 294 DISPATCH_ALWAYS_INLINE DISPATCH_CONST
 295 static inline dispatch_queue_t
 296 _dispatch_get_root_queue(long priority, bool overcommit)
 297 {
 298         if (overcommit) switch (priority) {
 299         case DISPATCH_QUEUE_PRIORITY_BACKGROUND:
 300 #if !DISPATCH_NO_BG_PRIORITY
 301                 return &_dispatch_root_queues[
 302                                 DISPATCH_ROOT_QUEUE_IDX_BACKGROUND_OVERCOMMIT_PRIORITY];
 303 #endif
 304         case DISPATCH_QUEUE_PRIORITY_LOW:
 305         case DISPATCH_QUEUE_PRIORITY_NON_INTERACTIVE:
 306                 return &_dispatch_root_queues[
 307                                 DISPATCH_ROOT_QUEUE_IDX_LOW_OVERCOMMIT_PRIORITY];
 308         case DISPATCH_QUEUE_PRIORITY_DEFAULT:
 309                 return &_dispatch_root_queues[
 310                                 DISPATCH_ROOT_QUEUE_IDX_DEFAULT_OVERCOMMIT_PRIORITY];
 311         case DISPATCH_QUEUE_PRIORITY_HIGH:
 312                 return &_dispatch_root_queues[
 313                                 DISPATCH_ROOT_QUEUE_IDX_HIGH_OVERCOMMIT_PRIORITY];
 314         }
 315         switch (priority) {
 316         case DISPATCH_QUEUE_PRIORITY_BACKGROUND:
 317 #if !DISPATCH_NO_BG_PRIORITY
 318                 return &_dispatch_root_queues[
 319                                 DISPATCH_ROOT_QUEUE_IDX_BACKGROUND_PRIORITY];
 320 #endif
 321         case DISPATCH_QUEUE_PRIORITY_LOW:
 322         case DISPATCH_QUEUE_PRIORITY_NON_INTERACTIVE:
 323                 return &_dispatch_root_queues[DISPATCH_ROOT_QUEUE_IDX_LOW_PRIORITY];
 324         case DISPATCH_QUEUE_PRIORITY_DEFAULT:
 325                 return &_dispatch_root_queues[DISPATCH_ROOT_QUEUE_IDX_DEFAULT_PRIORITY];
 326         case DISPATCH_QUEUE_PRIORITY_HIGH:
 327                 return &_dispatch_root_queues[DISPATCH_ROOT_QUEUE_IDX_HIGH_PRIORITY];
 328         default:
 329                 return NULL;
 330         }
 331 }
 332
 333 // Note to later developers: ensure that any initialization changes are
 334 // made for statically allocated queues (i.e. _dispatch_main_q).
 335 static inline void
 336 _dispatch_queue_init(dispatch_queue_t dq)
 337 {
 338         dq->do_next = (struct dispatch_queue_s *)DISPATCH_OBJECT_LISTLESS;
 339
 340         dq->dq_running = 0;
 341         dq->dq_width = 1;
 342         dq->dq_serialnum = dispatch_atomic_inc_orig(&_dispatch_queue_serial_numbers,
 343                         relaxed);
 344 }
 345
 346 DISPATCH_ALWAYS_INLINE
 347 static inline void
 348 _dispatch_queue_set_bound_thread(dispatch_queue_t dq)
 349 {
 350         //Tag thread-bound queues with the owning thread
 351         dispatch_assert(dq->dq_is_thread_bound);
 352         dq->do_finalizer = (void*)_dispatch_thread_self();
 353 }
 354
 355 DISPATCH_ALWAYS_INLINE
 356 static inline void
 357 _dispatch_queue_clear_bound_thread(dispatch_queue_t dq)
 358 {
 359         dispatch_assert(dq->dq_is_thread_bound);
 360         dq->do_finalizer = NULL;
 361 }
 362
 363 DISPATCH_ALWAYS_INLINE
 364 static inline pthread_t
 365 _dispatch_queue_get_bound_thread(dispatch_queue_t dq)
 366 {
 367         dispatch_assert(dq->dq_is_thread_bound);
 368         return (pthread_t)dq->do_finalizer;
 369 }
 370
 371 #ifndef DISPATCH_CONTINUATION_CACHE_LIMIT
 372 #if TARGET_OS_EMBEDDED
 373 #define DISPATCH_CONTINUATION_CACHE_LIMIT 112 // one 256k heap for 64 threads
 374 #define DISPATCH_CONTINUATION_CACHE_LIMIT_MEMORYSTATUS_PRESSURE_WARN 16
 375 #else
 376 #define DISPATCH_CONTINUATION_CACHE_LIMIT 65536
 377 #define DISPATCH_CONTINUATION_CACHE_LIMIT_MEMORYSTATUS_PRESSURE_WARN 128
 378 #endif
 379 #endif
 380
 381 dispatch_continuation_t _dispatch_continuation_alloc_from_heap(void);
 382 void _dispatch_continuation_free_to_heap(dispatch_continuation_t c);
 383
 384 #if DISPATCH_USE_MEMORYSTATUS_SOURCE
 385 extern int _dispatch_continuation_cache_limit;
 386 void _dispatch_continuation_free_to_cache_limit(dispatch_continuation_t c);
 387 #else
 388 #define _dispatch_continuation_cache_limit DISPATCH_CONTINUATION_CACHE_LIMIT
 389 #define _dispatch_continuation_free_to_cache_limit(c) \
 390                 _dispatch_continuation_free_to_heap(c)
 391 #endif
 392
 393 DISPATCH_ALWAYS_INLINE
 394 static inline dispatch_continuation_t
 395 _dispatch_continuation_alloc_cacheonly(void)
 396 {
 397         dispatch_continuation_t dc = (dispatch_continuation_t)
 398                         fastpath(_dispatch_thread_getspecific(dispatch_cache_key));
 399         if (dc) {
 400                 _dispatch_thread_setspecific(dispatch_cache_key, dc->do_next);
 401         }
 402         return dc;
 403 }
 404
 405 DISPATCH_ALWAYS_INLINE
 406 static inline dispatch_continuation_t
 407 _dispatch_continuation_alloc(void)
 408 {
 409         dispatch_continuation_t dc =
 410                         fastpath(_dispatch_continuation_alloc_cacheonly());
 411         if(!dc) {
 412                 return _dispatch_continuation_alloc_from_heap();
 413         }
 414         return dc;
 415 }
 416
 417 DISPATCH_ALWAYS_INLINE
 418 static inline dispatch_continuation_t
 419 _dispatch_continuation_free_cacheonly(dispatch_continuation_t dc)
 420 {
 421         dispatch_continuation_t prev_dc = (dispatch_continuation_t)
 422                         fastpath(_dispatch_thread_getspecific(dispatch_cache_key));
 423         int cnt = prev_dc ? prev_dc->do_ref_cnt + 1 : 1;
 424         // Cap continuation cache
 425         if (slowpath(cnt > _dispatch_continuation_cache_limit)) {
 426                 return dc;
 427         }
 428         dc->do_next = prev_dc;
 429         dc->do_ref_cnt = cnt;
 430         _dispatch_thread_setspecific(dispatch_cache_key, dc);
 431         return NULL;
 432 }
 433
 434 DISPATCH_ALWAYS_INLINE
 435 static inline void
 436 _dispatch_continuation_free(dispatch_continuation_t dc)
 437 {
 438         dc = _dispatch_continuation_free_cacheonly(dc);
 439         if (slowpath(dc)) {
 440                 _dispatch_continuation_free_to_cache_limit(dc);
 441         }
 442 }
 443 #endif // !(USE_OBJC && __OBJC2__)
 444
 445 #endif