libobjc/thr.c

   1 /* GNU Objective C Runtime Thread Interface
   2    Copyright (C) 1996-2014 Free Software Foundation, Inc.
   3    Contributed by Galen C. Hunt (gchunt@cs.rochester.edu)
   4
   5 This file is part of GCC.
   6
   7 GCC is free software; you can redistribute it and/or modify it under the
   8 terms of the GNU General Public License as published by the Free Software
   9 Foundation; either version 3, or (at your option) any later version.
  10
  11 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
  12 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  13 FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
  14 details.
  15
  16 Under Section 7 of GPL version 3, you are granted additional
  17 permissions described in the GCC Runtime Library Exception, version
  18 3.1, as published by the Free Software Foundation.
  19
  20 You should have received a copy of the GNU General Public License and
  21 a copy of the GCC Runtime Library Exception along with this program;
  22 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 <http://www.gnu.org/licenses/>.  */
  24
  25 #include "objc-private/common.h"
  26 #include "objc-private/error.h"
  27 #define _LIBOBJC
  28 /* The line below is needed for declarations of functions such as
  29    pthread_mutexattr_settype, without which gthr-posix.h may fail to
  30    compile within libobjc.  */
  31 #define _XOPEN_SOURCE 500
  32 #include "config.h"
  33 #include "tconfig.h"
  34 #include "coretypes.h"
  35 #include "tm.h"
  36 #include "defaults.h"
  37 #include "objc/thr.h"
  38 #include "objc/message.h" /* For objc_msg_lookup().  */
  39 #include "objc/runtime.h"
  40 #include "objc-private/module-abi-8.h"
  41 #include "objc-private/runtime.h"
  42 #include <gthr.h>
  43
  44 #include <stdlib.h>
  45
  46 /* Global exit status. */
  47 int __objc_thread_exit_status = 0;
  48
  49 /* Flag which lets us know if we ever became multi threaded.  */
  50 int __objc_is_multi_threaded = 0;
  51
  52 /* The hook function called when the runtime becomes multi
  53    threaded.  */
  54 objc_thread_callback _objc_became_multi_threaded = NULL;
  55
  56 /* Use this to set the hook function that will be called when the
  57    runtime initially becomes multi threaded.  The hook function is
  58    only called once, meaning only when the 2nd thread is spawned, not
  59    for each and every thread.
  60
  61    It returns the previous hook function or NULL if there is none.
  62
  63    A program outside of the runtime could set this to some function so
  64    it can be informed; for example, the GNUstep Base Library sets it
  65    so it can implement the NSBecomingMultiThreaded notification.  */
  66 objc_thread_callback objc_set_thread_callback (objc_thread_callback func)
  67 {
  68   objc_thread_callback temp = _objc_became_multi_threaded;
  69   _objc_became_multi_threaded = func;
  70   return temp;
  71 }
  72
  73 /* Private functions.
  74
  75    These functions are utilized by the runtime, but they are not
  76    considered part of the public interface.  */
  77
  78 /* Initialize the threads subsystem.  */
  79 int
  80 __objc_init_thread_system(void)
  81 {
  82   return __gthread_objc_init_thread_system ();
  83 }
  84
  85 /* First function called in a thread, starts everything else.
  86
  87    This function is passed to the backend by objc_thread_detach as the
  88    starting function for a new thread.  */
  89 struct __objc_thread_start_state
  90 {
  91   SEL selector;
  92   id object;
  93   id argument;
  94 };
  95
  96 static void __attribute__((noreturn))
  97 __objc_thread_detach_function (struct __objc_thread_start_state *istate)
  98 {
  99   /* Valid state? */
 100   if (istate)
 101     {
 102       id (*imp) (id, SEL, id);
 103       SEL selector = istate->selector;
 104       id object   = istate->object;
 105       id argument = istate->argument;
 106
 107       /* Don't need anymore so free it.  */
 108       objc_free (istate);
 109
 110       /* Clear out the thread local storage.  */
 111       objc_thread_set_data (NULL);
 112
 113       /* Check to see if we just became multi threaded. */
 114       if (! __objc_is_multi_threaded)
 115         {
 116           __objc_is_multi_threaded = 1;
 117
 118           /* Call the hook function.  */
 119           if (_objc_became_multi_threaded != NULL)
 120             (*_objc_became_multi_threaded) ();
 121         }
 122
 123       /* Call the method.  */
 124       if ((imp = (id (*) (id, SEL, id))objc_msg_lookup (object, selector)))
 125         (*imp) (object, selector, argument);
 126       else
 127         {
 128           /* FIXME: Should we abort here ? */
 129           _objc_abort ("objc_thread_detach called with bad selector.\n");
 130         }
 131     }
 132   else
 133     {
 134       /* FIXME: Should we abort here ? */
 135       _objc_abort ("objc_thread_detach called with NULL state.\n");
 136     }
 137
 138   /* Exit the thread.  */
 139   objc_thread_exit ();
 140
 141   /* Make sure compiler detects no return.  */
 142   __builtin_trap ();
 143 }
 144
 145 /* Public functions.
 146
 147    These functions constitute the public interface to the Objective-C
 148    thread and mutex functionality.  */
 149
 150 /* Detach a new thread of execution and return its id.  Returns NULL
 151    if fails.  Thread is started by sending message with selector to
 152    object.  Message takes a single argument.  */
 153 objc_thread_t
 154 objc_thread_detach (SEL selector, id object, id argument)
 155 {
 156   struct __objc_thread_start_state *istate;
 157   objc_thread_t        thread_id = NULL;
 158
 159   /* Allocate the state structure.  */
 160   if (!(istate = (struct __objc_thread_start_state *)objc_malloc
 161         (sizeof (*istate))))
 162     return NULL;
 163
 164   /* Initialize the state structure.  */
 165   istate->selector = selector;
 166   istate->object = object;
 167   istate->argument = argument;
 168
 169   /* Lock access.  */
 170   objc_mutex_lock (__objc_runtime_mutex);
 171
 172   /* Call the backend to spawn the thread.  */
 173   if ((thread_id = __gthread_objc_thread_detach ((void *)__objc_thread_detach_function,
 174                                                  istate)) == NULL)
 175     {
 176       /* Failed!  */
 177       objc_mutex_unlock (__objc_runtime_mutex);
 178       objc_free (istate);
 179       return NULL;
 180     }
 181
 182   /* Increment our thread counter.  */
 183   __objc_runtime_threads_alive++;
 184   objc_mutex_unlock (__objc_runtime_mutex);
 185
 186   return thread_id;
 187 }
 188
 189 /* Set the current thread's priority.  */
 190 int
 191 objc_thread_set_priority (int priority)
 192 {
 193   return __gthread_objc_thread_set_priority (priority);
 194 }
 195
 196 /* Return the current thread's priority.  */
 197 int
 198 objc_thread_get_priority (void)
 199 {
 200   return __gthread_objc_thread_get_priority ();
 201 }
 202
 203 /* Yield our process time to another thread.  Any BUSY waiting that is
 204    done by a thread should use this function to make sure that other
 205    threads can make progress even on a lazy uniprocessor system.  */
 206 void
 207 objc_thread_yield (void)
 208 {
 209   __gthread_objc_thread_yield ();
 210 }
 211
 212 /* Terminate the current tread.  Doesn't return.  Actually, if it
 213    failed returns -1.  */
 214 int
 215 objc_thread_exit (void)
 216 {
 217   /* Decrement our counter of the number of threads alive.  */
 218   objc_mutex_lock (__objc_runtime_mutex);
 219   __objc_runtime_threads_alive--;
 220   objc_mutex_unlock (__objc_runtime_mutex);
 221
 222   /* Call the backend to terminate the thread.  */
 223   return __gthread_objc_thread_exit ();
 224 }
 225
 226 /* Returns an integer value which uniquely describes a thread.  Must
 227    not be NULL which is reserved as a marker for "no thread".  */
 228 objc_thread_t
 229 objc_thread_id (void)
 230 {
 231   return __gthread_objc_thread_id ();
 232 }
 233
 234 /* Sets the thread's local storage pointer.  Returns 0 if successful
 235    or -1 if failed.  */
 236 int
 237 objc_thread_set_data (void *value)
 238 {
 239   return __gthread_objc_thread_set_data (value);
 240 }
 241
 242 /* Returns the thread's local storage pointer.  Returns NULL on
 243    failure.  */
 244 void *
 245 objc_thread_get_data (void)
 246 {
 247   return __gthread_objc_thread_get_data ();
 248 }
 249
 250 /* Public mutex functions */
 251
 252 /* Allocate a mutex.  Return the mutex pointer if successful or NULL
 253    if the allocation failed for any reason.  */
 254 objc_mutex_t
 255 objc_mutex_allocate (void)
 256 {
 257   objc_mutex_t mutex;
 258
 259   /* Allocate the mutex structure.  */
 260   if (! (mutex = (objc_mutex_t)objc_malloc (sizeof (struct objc_mutex))))
 261     return NULL;
 262
 263   /* Call backend to create the mutex.  */
 264   if (__gthread_objc_mutex_allocate (mutex))
 265     {
 266       /* Failed!  */
 267       objc_free (mutex);
 268       return NULL;
 269     }
 270
 271   /* Initialize mutex.  */
 272   mutex->owner = NULL;
 273   mutex->depth = 0;
 274   return mutex;
 275 }
 276
 277 /* Deallocate a mutex.  Note that this includes an implicit mutex_lock
 278    to insure that no one else is using the lock.  It is legal to
 279    deallocate a lock if we have a lock on it, but illegal to
 280    deallocate a lock held by anyone else.  Returns the number of locks
 281    on the thread.  (1 for deallocate).  */
 282 int
 283 objc_mutex_deallocate (objc_mutex_t mutex)
 284 {
 285   int depth;
 286
 287   /* Valid mutex?  */
 288   if (! mutex)
 289     return -1;
 290
 291   /* Acquire lock on mutex.  */
 292   depth = objc_mutex_lock (mutex);
 293
 294   /* Call backend to destroy mutex.  */
 295   if (__gthread_objc_mutex_deallocate (mutex))
 296     return -1;
 297
 298   /* Free the mutex structure.  */
 299   objc_free (mutex);
 300
 301   /* Return last depth.  */
 302   return depth;
 303 }
 304
 305 /* Grab a lock on a mutex.  If this thread already has a lock on this
 306    mutex then we increment the lock count.  If another thread has a
 307    lock on the mutex we block and wait for the thread to release the
 308    lock.  Returns the lock count on the mutex held by this thread.  */
 309 int
 310 objc_mutex_lock (objc_mutex_t mutex)
 311 {
 312   objc_thread_t thread_id;
 313   int status;
 314
 315   /* Valid mutex?  */
 316   if (! mutex)
 317     return -1;
 318
 319   /* If we already own the lock then increment depth.  */
 320   thread_id = __gthread_objc_thread_id ();
 321   if (mutex->owner == thread_id)
 322     return ++mutex->depth;
 323
 324   /* Call the backend to lock the mutex.  */
 325   status = __gthread_objc_mutex_lock (mutex);
 326
 327   /* Failed?  */
 328   if (status)
 329     return status;
 330
 331   /* Successfully locked the thread.  */
 332   mutex->owner = thread_id;
 333   return mutex->depth = 1;
 334 }
 335
 336 /* Try to grab a lock on a mutex.  If this thread already has a lock
 337    on this mutex then we increment the lock count and return it.  If
 338    another thread has a lock on the mutex returns -1.  */
 339 int
 340 objc_mutex_trylock (objc_mutex_t mutex)
 341 {
 342   objc_thread_t thread_id;
 343   int status;
 344
 345   /* Valid mutex?  */
 346   if (! mutex)
 347     return -1;
 348
 349   /* If we already own the lock then increment depth.  */
 350   thread_id = __gthread_objc_thread_id ();
 351   if (mutex->owner == thread_id)
 352     return ++mutex->depth;
 353
 354   /* Call the backend to try to lock the mutex.  */
 355   status = __gthread_objc_mutex_trylock (mutex);
 356
 357   /* Failed?  */
 358   if (status)
 359     return status;
 360
 361   /* Successfully locked the thread.  */
 362   mutex->owner = thread_id;
 363   return mutex->depth = 1;
 364 }
 365
 366 /* Unlocks the mutex by one level.  Decrements the lock count on this
 367    mutex by one.  If the lock count reaches zero, release the lock on
 368    the mutex.  Returns the lock count on the mutex.  It is an error to
 369    attempt to unlock a mutex which this thread doesn't hold in which
 370    case return -1 and the mutex is unaffected.  */
 371 int
 372 objc_mutex_unlock (objc_mutex_t mutex)
 373 {
 374   objc_thread_t thread_id;
 375   int status;
 376
 377   /* Valid mutex?  */
 378   if (! mutex)
 379     return -1;
 380
 381   /* If another thread owns the lock then abort.  */
 382   thread_id = __gthread_objc_thread_id ();
 383   if (mutex->owner != thread_id)
 384     return -1;
 385
 386   /* Decrement depth and return.  */
 387   if (mutex->depth > 1)
 388     return --mutex->depth;
 389
 390   /* Depth down to zero so we are no longer the owner.  */
 391   mutex->depth = 0;
 392   mutex->owner = NULL;
 393
 394   /* Have the backend unlock the mutex.  */
 395   status = __gthread_objc_mutex_unlock (mutex);
 396
 397   /* Failed?  */
 398   if (status)
 399     return status;
 400
 401   return 0;
 402 }
 403
 404 /* Public condition mutex functions */
 405
 406 /* Allocate a condition.  Return the condition pointer if successful
 407    or NULL if the allocation failed for any reason.  */
 408 objc_condition_t
 409 objc_condition_allocate (void)
 410 {
 411   objc_condition_t condition;
 412
 413   /* Allocate the condition mutex structure.  */
 414   if (! (condition =
 415          (objc_condition_t) objc_malloc (sizeof (struct objc_condition))))
 416     return NULL;
 417
 418   /* Call the backend to create the condition mutex.  */
 419   if (__gthread_objc_condition_allocate (condition))
 420     {
 421       /* Failed!  */
 422       objc_free (condition);
 423       return NULL;
 424     }
 425
 426   /* Success!  */
 427   return condition;
 428 }
 429
 430 /* Deallocate a condition. Note that this includes an implicit
 431    condition_broadcast to insure that waiting threads have the
 432    opportunity to wake.  It is legal to dealloc a condition only if no
 433    other thread is/will be using it. Here we do NOT check for other
 434    threads waiting but just wake them up.  */
 435 int
 436 objc_condition_deallocate (objc_condition_t condition)
 437 {
 438   /* Broadcast the condition.  */
 439   if (objc_condition_broadcast (condition))
 440     return -1;
 441
 442   /* Call the backend to destroy.  */
 443   if (__gthread_objc_condition_deallocate (condition))
 444     return -1;
 445
 446   /* Free the condition mutex structure.  */
 447   objc_free (condition);
 448
 449   return 0;
 450 }
 451
 452 /* Wait on the condition unlocking the mutex until
 453    objc_condition_signal () or objc_condition_broadcast () are called
 454    for the same condition. The given mutex *must* have the depth set
 455    to 1 so that it can be unlocked here, so that someone else can lock
 456    it and signal/broadcast the condition.  The mutex is used to lock
 457    access to the shared data that make up the "condition"
 458    predicate.  */
 459 int
 460 objc_condition_wait (objc_condition_t condition, objc_mutex_t mutex)
 461 {
 462   objc_thread_t thread_id;
 463
 464   /* Valid arguments?  */
 465   if (! mutex || ! condition)
 466     return -1;
 467
 468   /* Make sure we are owner of mutex.  */
 469   thread_id = __gthread_objc_thread_id ();
 470   if (mutex->owner != thread_id)
 471     return -1;
 472
 473   /* Cannot be locked more than once.  */
 474   if (mutex->depth > 1)
 475     return -1;
 476
 477   /* Virtually unlock the mutex.  */
 478   mutex->depth = 0;
 479   mutex->owner = (objc_thread_t)NULL;
 480
 481   /* Call the backend to wait.  */
 482   __gthread_objc_condition_wait (condition, mutex);
 483
 484   /* Make ourselves owner of the mutex.  */
 485   mutex->owner = thread_id;
 486   mutex->depth = 1;
 487
 488   return 0;
 489 }
 490
 491 /* Wake up all threads waiting on this condition. It is recommended
 492    that the called would lock the same mutex as the threads in
 493    objc_condition_wait before changing the "condition predicate" and
 494    make this call and unlock it right away after this call.  */
 495 int
 496 objc_condition_broadcast (objc_condition_t condition)
 497 {
 498   /* Valid condition mutex?  */
 499   if (! condition)
 500     return -1;
 501
 502   return __gthread_objc_condition_broadcast (condition);
 503 }
 504
 505 /* Wake up one thread waiting on this condition. It is recommended
 506    that the called would lock the same mutex as the threads in
 507    objc_condition_wait before changing the "condition predicate" and
 508    make this call and unlock it right away after this call.  */
 509 int
 510 objc_condition_signal (objc_condition_t condition)
 511 {
 512   /* Valid condition mutex?  */
 513   if (! condition)
 514     return -1;
 515
 516   return __gthread_objc_condition_signal (condition);
 517 }
 518
 519 /* Make the objc thread system aware that a thread which is managed
 520    (started, stopped) by external code could access objc facilities
 521    from now on.  This is used when you are interfacing with some
 522    external non-objc-based environment/system - you must call
 523    objc_thread_add () before an alien thread makes any calls to
 524    Objective-C.  Do not cause the _objc_became_multi_threaded hook to
 525    be executed. */
 526 void
 527 objc_thread_add (void)
 528 {
 529   objc_mutex_lock (__objc_runtime_mutex);
 530   __objc_is_multi_threaded = 1;
 531   __objc_runtime_threads_alive++;
 532   objc_mutex_unlock (__objc_runtime_mutex);
 533 }
 534
 535 /* Make the objc thread system aware that a thread managed (started,
 536    stopped) by some external code will no longer access objc and thus
 537    can be forgotten by the objc thread system.  Call
 538    objc_thread_remove () when your alien thread is done with making
 539    calls to Objective-C. */
 540 void
 541 objc_thread_remove (void)
 542 {
 543   objc_mutex_lock (__objc_runtime_mutex);
 544   __objc_runtime_threads_alive--;
 545   objc_mutex_unlock (__objc_runtime_mutex);
 546 }
 547