libobjc/thr.c

   1 /* GNU Objective C Runtime Thread Interface
   2    Copyright (C) 1996, 1997, 2009 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
  26 #include <stdlib.h>
  27 #include "objc/runtime.h"
  28
  29 /* Global exit status. */
  30 int __objc_thread_exit_status = 0;
  31
  32 /* Flag which lets us know if we ever became multi threaded */
  33 int __objc_is_multi_threaded = 0;
  34
  35 /* The hook function called when the runtime becomes multi threaded */
  36 objc_thread_callback _objc_became_multi_threaded = NULL;
  37
  38 /*
  39   Use this to set the hook function that will be called when the
  40   runtime initially becomes multi threaded.
  41   The hook function is only called once, meaning only when the
  42   2nd thread is spawned, not for each and every thread.
  43
  44   It returns the previous hook function or NULL if there is none.
  45
  46   A program outside of the runtime could set this to some function so
  47   it can be informed; for example, the GNUstep Base Library sets it
  48   so it can implement the NSBecomingMultiThreaded notification.
  49   */
  50 objc_thread_callback objc_set_thread_callback (objc_thread_callback func)
  51 {
  52   objc_thread_callback temp = _objc_became_multi_threaded;
  53   _objc_became_multi_threaded = func;
  54   return temp;
  55 }
  56
  57 /*
  58   Private functions
  59
  60   These functions are utilized by the frontend, but they are not
  61   considered part of the public interface.
  62   */
  63
  64 /*
  65   First function called in a thread, starts everything else.
  66
  67   This function is passed to the backend by objc_thread_detach
  68   as the starting function for a new thread.
  69  */
  70 struct __objc_thread_start_state
  71 {
  72   SEL selector;
  73   id object;
  74   id argument;
  75 };
  76
  77 static void __attribute__((noreturn))
  78 __objc_thread_detach_function (struct __objc_thread_start_state *istate)
  79 {
  80   /* Valid state? */
  81   if (istate) {
  82     id (*imp) (id, SEL, id);
  83     SEL selector = istate->selector;
  84     id object   = istate->object;
  85     id argument = istate->argument;
  86
  87     /* Don't need anymore so free it */
  88     objc_free (istate);
  89
  90     /* Clear out the thread local storage */
  91     objc_thread_set_data (NULL);
  92
  93     /* Check to see if we just became multi threaded */
  94     if (! __objc_is_multi_threaded)
  95       {
  96         __objc_is_multi_threaded = 1;
  97
  98         /* Call the hook function */
  99         if (_objc_became_multi_threaded != NULL)
 100           (*_objc_became_multi_threaded) ();
 101       }
 102
 103     /* Call the method */
 104     if ((imp = (id (*) (id, SEL, id))objc_msg_lookup (object, selector)))
 105         (*imp) (object, selector, argument);
 106     else
 107       objc_error (object, OBJC_ERR_UNIMPLEMENTED,
 108                   "objc_thread_detach called with bad selector.\n");
 109   }
 110   else
 111     objc_error (nil, OBJC_ERR_BAD_STATE,
 112                 "objc_thread_detach called with NULL state.\n");
 113
 114   /* Exit the thread */
 115   objc_thread_exit ();
 116
 117   /* Make sure compiler detects no return.  */
 118   __builtin_trap ();
 119 }
 120
 121 /*
 122   Frontend functions
 123
 124   These functions constitute the public interface to the Objective-C thread
 125   and mutex functionality.
 126   */
 127
 128 /* Frontend thread functions */
 129
 130 /*
 131   Detach a new thread of execution and return its id.  Returns NULL if fails.
 132   Thread is started by sending message with selector to object.  Message
 133   takes a single argument.
 134   */
 135 objc_thread_t
 136 objc_thread_detach (SEL selector, id object, id argument)
 137 {
 138   struct __objc_thread_start_state *istate;
 139   objc_thread_t        thread_id = NULL;
 140
 141   /* Allocate the state structure */
 142   if (! (istate = (struct __objc_thread_start_state *)
 143          objc_malloc (sizeof (*istate))))
 144     return NULL;
 145
 146   /* Initialize the state structure */
 147   istate->selector = selector;
 148   istate->object = object;
 149   istate->argument = argument;
 150
 151   /* lock access */
 152   objc_mutex_lock (__objc_runtime_mutex);
 153
 154   /* Call the backend to spawn the thread */
 155   if ((thread_id = __objc_thread_detach ((void *)__objc_thread_detach_function,
 156                                          istate)) == NULL)
 157     {
 158       /* failed! */
 159       objc_mutex_unlock (__objc_runtime_mutex);
 160       objc_free (istate);
 161       return NULL;
 162     }
 163
 164   /* Increment our thread counter */
 165   __objc_runtime_threads_alive++;
 166   objc_mutex_unlock (__objc_runtime_mutex);
 167
 168   return thread_id;
 169 }
 170
 171 /* Set the current thread's priority. */
 172 int
 173 objc_thread_set_priority (int priority)
 174 {
 175   /* Call the backend */
 176   return __objc_thread_set_priority (priority);
 177 }
 178
 179 /* Return the current thread's priority. */
 180 int
 181 objc_thread_get_priority (void)
 182 {
 183   /* Call the backend */
 184   return __objc_thread_get_priority ();
 185 }
 186
 187 /*
 188   Yield our process time to another thread.  Any BUSY waiting that is done
 189   by a thread should use this function to make sure that other threads can
 190   make progress even on a lazy uniprocessor system.
 191   */
 192 void
 193 objc_thread_yield (void)
 194 {
 195   /* Call the backend */
 196   __objc_thread_yield ();
 197 }
 198
 199 /*
 200   Terminate the current tread.  Doesn't return.
 201   Actually, if it failed returns -1.
 202   */
 203 int
 204 objc_thread_exit (void)
 205 {
 206   /* Decrement our counter of the number of threads alive */
 207   objc_mutex_lock (__objc_runtime_mutex);
 208   __objc_runtime_threads_alive--;
 209   objc_mutex_unlock (__objc_runtime_mutex);
 210
 211   /* Call the backend to terminate the thread */
 212   return __objc_thread_exit ();
 213 }
 214
 215 /*
 216   Returns an integer value which uniquely describes a thread.  Must not be
 217   NULL which is reserved as a marker for "no thread".
 218   */
 219 objc_thread_t
 220 objc_thread_id (void)
 221 {
 222   /* Call the backend */
 223   return __objc_thread_id ();
 224 }
 225
 226 /*
 227   Sets the thread's local storage pointer.
 228   Returns 0 if successful or -1 if failed.
 229   */
 230 int
 231 objc_thread_set_data (void *value)
 232 {
 233   /* Call the backend */
 234   return __objc_thread_set_data (value);
 235 }
 236
 237 /*
 238   Returns the thread's local storage pointer.  Returns NULL on failure.
 239   */
 240 void *
 241 objc_thread_get_data (void)
 242 {
 243   /* Call the backend */
 244   return __objc_thread_get_data ();
 245 }
 246
 247 /* Frontend mutex functions */
 248
 249 /*
 250   Allocate a mutex.  Return the mutex pointer if successful or NULL if the
 251   allocation failed for any reason.
 252   */
 253 objc_mutex_t
 254 objc_mutex_allocate (void)
 255 {
 256   objc_mutex_t mutex;
 257
 258   /* Allocate the mutex structure */
 259   if (! (mutex = (objc_mutex_t)objc_malloc (sizeof (struct objc_mutex))))
 260     return NULL;
 261
 262   /* Call backend to create the mutex */
 263   if (__objc_mutex_allocate (mutex))
 264     {
 265       /* failed! */
 266       objc_free (mutex);
 267       return NULL;
 268     }
 269
 270   /* Initialize mutex */
 271   mutex->owner = NULL;
 272   mutex->depth = 0;
 273   return mutex;
 274 }
 275
 276 /*
 277   Deallocate a mutex.  Note that this includes an implicit mutex_lock to
 278   insure that no one else is using the lock.  It is legal to deallocate
 279   a lock if we have a lock on it, but illegal to deallocate a lock held
 280   by anyone else.
 281   Returns the number of locks on the thread.  (1 for deallocate).
 282   */
 283 int
 284 objc_mutex_deallocate (objc_mutex_t mutex)
 285 {
 286   int depth;
 287
 288   /* Valid mutex? */
 289   if (! mutex)
 290     return -1;
 291
 292   /* Acquire lock on mutex */
 293   depth = objc_mutex_lock (mutex);
 294
 295   /* Call backend to destroy mutex */
 296   if (__objc_mutex_deallocate (mutex))
 297     return -1;
 298
 299   /* Free the mutex structure */
 300   objc_free (mutex);
 301
 302   /* Return last depth */
 303   return depth;
 304 }
 305
 306 /*
 307   Grab a lock on a mutex.  If this thread already has a lock on this mutex
 308   then we increment the lock count.  If another thread has a lock on the
 309   mutex we block and wait for the thread to release the lock.
 310   Returns the lock count on the mutex held by this thread.
 311   */
 312 int
 313 objc_mutex_lock (objc_mutex_t mutex)
 314 {
 315   objc_thread_t thread_id;
 316   int status;
 317
 318   /* Valid mutex? */
 319   if (! mutex)
 320     return -1;
 321
 322   /* If we already own the lock then increment depth */
 323   thread_id = __objc_thread_id ();
 324   if (mutex->owner == thread_id)
 325     return ++mutex->depth;
 326
 327   /* Call the backend to lock the mutex */
 328   status = __objc_mutex_lock (mutex);
 329
 330   /* Failed? */
 331   if (status)
 332     return status;
 333
 334   /* Successfully locked the thread */
 335   mutex->owner = thread_id;
 336   return mutex->depth = 1;
 337 }
 338
 339 /*
 340   Try to grab a lock on a mutex.  If this thread already has a lock on
 341   this mutex then we increment the lock count and return it.  If another
 342   thread has a lock on the mutex returns -1.
 343   */
 344 int
 345 objc_mutex_trylock (objc_mutex_t mutex)
 346 {
 347   objc_thread_t thread_id;
 348   int status;
 349
 350   /* Valid mutex? */
 351   if (! mutex)
 352     return -1;
 353
 354   /* If we already own the lock then increment depth */
 355   thread_id = __objc_thread_id ();
 356   if (mutex->owner == thread_id)
 357     return ++mutex->depth;
 358
 359   /* Call the backend to try to lock the mutex */
 360   status = __objc_mutex_trylock (mutex);
 361
 362   /* Failed? */
 363   if (status)
 364     return status;
 365
 366   /* Successfully locked the thread */
 367   mutex->owner = thread_id;
 368   return mutex->depth = 1;
 369 }
 370
 371 /*
 372   Unlocks the mutex by one level.
 373   Decrements the lock count on this mutex by one.
 374   If the lock count reaches zero, release the lock on the mutex.
 375   Returns the lock count on the mutex.
 376   It is an error to attempt to unlock a mutex which this thread
 377   doesn't hold in which case return -1 and the mutex is unaffected.
 378   */
 379 int
 380 objc_mutex_unlock (objc_mutex_t mutex)
 381 {
 382   objc_thread_t thread_id;
 383   int status;
 384
 385   /* Valid mutex? */
 386   if (! mutex)
 387     return -1;
 388
 389   /* If another thread owns the lock then abort */
 390   thread_id = __objc_thread_id ();
 391   if (mutex->owner != thread_id)
 392     return -1;
 393
 394   /* Decrement depth and return */
 395   if (mutex->depth > 1)
 396     return --mutex->depth;
 397
 398   /* Depth down to zero so we are no longer the owner */
 399   mutex->depth = 0;
 400   mutex->owner = NULL;
 401
 402   /* Have the backend unlock the mutex */
 403   status = __objc_mutex_unlock (mutex);
 404
 405   /* Failed? */
 406   if (status)
 407     return status;
 408
 409   return 0;
 410 }
 411
 412 /* Frontend condition mutex functions */
 413
 414 /*
 415   Allocate a condition.  Return the condition pointer if successful or NULL
 416   if the allocation failed for any reason.
 417   */
 418 objc_condition_t
 419 objc_condition_allocate (void)
 420 {
 421   objc_condition_t condition;
 422
 423   /* Allocate the condition mutex structure */
 424   if (! (condition =
 425          (objc_condition_t) objc_malloc (sizeof (struct objc_condition))))
 426     return NULL;
 427
 428   /* Call the backend to create the condition mutex */
 429   if (__objc_condition_allocate (condition))
 430     {
 431       /* failed! */
 432       objc_free (condition);
 433       return NULL;
 434     }
 435
 436   /* Success! */
 437   return condition;
 438 }
 439
 440 /*
 441   Deallocate a condition. Note that this includes an implicit
 442   condition_broadcast to insure that waiting threads have the opportunity
 443   to wake.  It is legal to dealloc a condition only if no other
 444   thread is/will be using it. Here we do NOT check for other threads
 445   waiting but just wake them up.
 446   */
 447 int
 448 objc_condition_deallocate (objc_condition_t condition)
 449 {
 450   /* Broadcast the condition */
 451   if (objc_condition_broadcast (condition))
 452     return -1;
 453
 454   /* Call the backend to destroy */
 455   if (__objc_condition_deallocate (condition))
 456     return -1;
 457
 458   /* Free the condition mutex structure */
 459   objc_free (condition);
 460
 461   return 0;
 462 }
 463
 464 /*
 465   Wait on the condition unlocking the mutex until objc_condition_signal ()
 466   or objc_condition_broadcast () are called for the same condition. The
 467   given mutex *must* have the depth set to 1 so that it can be unlocked
 468   here, so that someone else can lock it and signal/broadcast the condition.
 469   The mutex is used to lock access to the shared data that make up the
 470   "condition" predicate.
 471   */
 472 int
 473 objc_condition_wait (objc_condition_t condition, objc_mutex_t mutex)
 474 {
 475   objc_thread_t thread_id;
 476
 477   /* Valid arguments? */
 478   if (! mutex || ! condition)
 479     return -1;
 480
 481   /* Make sure we are owner of mutex */
 482   thread_id = __objc_thread_id ();
 483   if (mutex->owner != thread_id)
 484     return -1;
 485
 486   /* Cannot be locked more than once */
 487   if (mutex->depth > 1)
 488     return -1;
 489
 490   /* Virtually unlock the mutex */
 491   mutex->depth = 0;
 492   mutex->owner = (objc_thread_t)NULL;
 493
 494   /* Call the backend to wait */
 495   __objc_condition_wait (condition, mutex);
 496
 497   /* Make ourselves owner of the mutex */
 498   mutex->owner = thread_id;
 499   mutex->depth = 1;
 500
 501   return 0;
 502 }
 503
 504 /*
 505   Wake up all threads waiting on this condition. It is recommended that
 506   the called would lock the same mutex as the threads in objc_condition_wait
 507   before changing the "condition predicate" and make this call and unlock it
 508   right away after this call.
 509   */
 510 int
 511 objc_condition_broadcast (objc_condition_t condition)
 512 {
 513   /* Valid condition mutex? */
 514   if (! condition)
 515     return -1;
 516
 517   return __objc_condition_broadcast (condition);
 518 }
 519
 520 /*
 521   Wake up one thread waiting on this condition. It is recommended that
 522   the called would lock the same mutex as the threads in objc_condition_wait
 523   before changing the "condition predicate" and make this call and unlock it
 524   right away after this call.
 525   */
 526 int
 527 objc_condition_signal (objc_condition_t condition)
 528 {
 529   /* Valid condition mutex? */
 530   if (! condition)
 531     return -1;
 532
 533   return __objc_condition_signal (condition);
 534 }
 535
 536 /* Make the objc thread system aware that a thread which is managed
 537    (started, stopped) by external code could access objc facilities
 538    from now on.  This is used when you are interfacing with some
 539    external non-objc-based environment/system - you must call
 540    objc_thread_add () before an alien thread makes any calls to
 541    Objective-C.  Do not cause the _objc_became_multi_threaded hook to
 542    be executed. */
 543 void
 544 objc_thread_add (void)
 545 {
 546   objc_mutex_lock (__objc_runtime_mutex);
 547   __objc_is_multi_threaded = 1;
 548   __objc_runtime_threads_alive++;
 549   objc_mutex_unlock (__objc_runtime_mutex);
 550 }
 551
 552 /* Make the objc thread system aware that a thread managed (started,
 553    stopped) by some external code will no longer access objc and thus
 554    can be forgotten by the objc thread system.  Call
 555    objc_thread_remove () when your alien thread is done with making
 556    calls to Objective-C. */
 557 void
 558 objc_thread_remove (void)
 559 {
 560   objc_mutex_lock (__objc_runtime_mutex);
 561   __objc_runtime_threads_alive--;
 562   objc_mutex_unlock (__objc_runtime_mutex);
 563 }
 564
 565 /* End of File */