libobjc/thr.c

   1 /* GNU Objective C Runtime Thread Interface
   2    Copyright (C) 1996, 1997, 2009, 2010 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.  Unfortunately, this breaks compilation on
  31    Tru64 UNIX V4.0F, so disable it there.  */
  32 #ifndef __osf__
  33 #define _XOPEN_SOURCE 500
  34 #endif
  35 #include "config.h"
  36 #include "tconfig.h"
  37 #include "coretypes.h"
  38 #include "tm.h"
  39 #include "defaults.h"
  40 #include "objc/thr.h"
  41 #include "objc/runtime.h"
  42 #include "objc-private/runtime.h"
  43 #include <gthr.h>
  44
  45 #include <stdlib.h>
  46
  47 /* Global exit status. */
  48 int __objc_thread_exit_status = 0;
  49
  50 /* Flag which lets us know if we ever became multi threaded */
  51 int __objc_is_multi_threaded = 0;
  52
  53 /* The hook function called when the runtime becomes multi threaded */
  54 objc_thread_callback _objc_became_multi_threaded = NULL;
  55
  56 /*
  57   Use this to set the hook function that will be called when the
  58   runtime initially becomes multi threaded.
  59   The hook function is only called once, meaning only when the
  60   2nd thread is spawned, not for each and every thread.
  61
  62   It returns the previous hook function or NULL if there is none.
  63
  64   A program outside of the runtime could set this to some function so
  65   it can be informed; for example, the GNUstep Base Library sets it
  66   so it can implement the NSBecomingMultiThreaded notification.
  67   */
  68 objc_thread_callback objc_set_thread_callback (objc_thread_callback func)
  69 {
  70   objc_thread_callback temp = _objc_became_multi_threaded;
  71   _objc_became_multi_threaded = func;
  72   return temp;
  73 }
  74
  75 /*
  76   Private functions
  77
  78   These functions are utilized by the frontend, but they are not
  79   considered part of the public interface.
  80   */
  81
  82 /* Initialize the threads subsystem. */
  83 int
  84 __objc_init_thread_system(void)
  85 {
  86   return __gthread_objc_init_thread_system ();
  87 }
  88
  89 /*
  90   First function called in a thread, starts everything else.
  91
  92   This function is passed to the backend by objc_thread_detach
  93   as the starting function for a new thread.
  94  */
  95 struct __objc_thread_start_state
  96 {
  97   SEL selector;
  98   id object;
  99   id argument;
 100 };
 101
 102 static void __attribute__((noreturn))
 103 __objc_thread_detach_function (struct __objc_thread_start_state *istate)
 104 {
 105   /* Valid state? */
 106   if (istate) {
 107     id (*imp) (id, SEL, id);
 108     SEL selector = istate->selector;
 109     id object   = istate->object;
 110     id argument = istate->argument;
 111
 112     /* Don't need anymore so free it */
 113     objc_free (istate);
 114
 115     /* Clear out the thread local storage */
 116     objc_thread_set_data (NULL);
 117
 118     /* Check to see if we just became multi threaded */
 119     if (! __objc_is_multi_threaded)
 120       {
 121         __objc_is_multi_threaded = 1;
 122
 123         /* Call the hook function */
 124         if (_objc_became_multi_threaded != NULL)
 125           (*_objc_became_multi_threaded) ();
 126       }
 127
 128     /* Call the method */
 129     if ((imp = (id (*) (id, SEL, id))objc_msg_lookup (object, selector)))
 130         (*imp) (object, selector, argument);
 131     else
 132       {
 133         /* FIXME: Should we abort here ? */
 134         _objc_abort ("objc_thread_detach called with bad selector.\n");
 135       }
 136   }
 137   else
 138     {
 139       /* FIXME: Should we abort here ? */
 140       _objc_abort ("objc_thread_detach called with NULL state.\n");
 141     }
 142
 143   /* Exit the thread */
 144   objc_thread_exit ();
 145
 146   /* Make sure compiler detects no return.  */
 147   __builtin_trap ();
 148 }
 149
 150 /*
 151   Frontend functions
 152
 153   These functions constitute the public interface to the Objective-C thread
 154   and mutex functionality.
 155   */
 156
 157 /* Frontend thread functions */
 158
 159 /*
 160   Detach a new thread of execution and return its id.  Returns NULL if fails.
 161   Thread is started by sending message with selector to object.  Message
 162   takes a single argument.
 163   */
 164 objc_thread_t
 165 objc_thread_detach (SEL selector, id object, id argument)
 166 {
 167   struct __objc_thread_start_state *istate;
 168   objc_thread_t        thread_id = NULL;
 169
 170   /* Allocate the state structure */
 171   if (! (istate = (struct __objc_thread_start_state *)
 172          objc_malloc (sizeof (*istate))))
 173     return NULL;
 174
 175   /* Initialize the state structure */
 176   istate->selector = selector;
 177   istate->object = object;
 178   istate->argument = argument;
 179
 180   /* lock access */
 181   objc_mutex_lock (__objc_runtime_mutex);
 182
 183   /* Call the backend to spawn the thread */
 184   if ((thread_id = __gthread_objc_thread_detach ((void *)__objc_thread_detach_function,
 185                                                  istate)) == NULL)
 186     {
 187       /* failed! */
 188       objc_mutex_unlock (__objc_runtime_mutex);
 189       objc_free (istate);
 190       return NULL;
 191     }
 192
 193   /* Increment our thread counter */
 194   __objc_runtime_threads_alive++;
 195   objc_mutex_unlock (__objc_runtime_mutex);
 196
 197   return thread_id;
 198 }
 199
 200 /* Set the current thread's priority. */
 201 int
 202 objc_thread_set_priority (int priority)
 203 {
 204   /* Call the backend */
 205   return __gthread_objc_thread_set_priority (priority);
 206 }
 207
 208 /* Return the current thread's priority. */
 209 int
 210 objc_thread_get_priority (void)
 211 {
 212   /* Call the backend */
 213   return __gthread_objc_thread_get_priority ();
 214 }
 215
 216 /*
 217   Yield our process time to another thread.  Any BUSY waiting that is done
 218   by a thread should use this function to make sure that other threads can
 219   make progress even on a lazy uniprocessor system.
 220   */
 221 void
 222 objc_thread_yield (void)
 223 {
 224   /* Call the backend */
 225   __gthread_objc_thread_yield ();
 226 }
 227
 228 /*
 229   Terminate the current tread.  Doesn't return.
 230   Actually, if it failed returns -1.
 231   */
 232 int
 233 objc_thread_exit (void)
 234 {
 235   /* Decrement our counter of the number of threads alive */
 236   objc_mutex_lock (__objc_runtime_mutex);
 237   __objc_runtime_threads_alive--;
 238   objc_mutex_unlock (__objc_runtime_mutex);
 239
 240   /* Call the backend to terminate the thread */
 241   return __gthread_objc_thread_exit ();
 242 }
 243
 244 /*
 245   Returns an integer value which uniquely describes a thread.  Must not be
 246   NULL which is reserved as a marker for "no thread".
 247   */
 248 objc_thread_t
 249 objc_thread_id (void)
 250 {
 251   /* Call the backend */
 252   return __gthread_objc_thread_id ();
 253 }
 254
 255 /*
 256   Sets the thread's local storage pointer.
 257   Returns 0 if successful or -1 if failed.
 258   */
 259 int
 260 objc_thread_set_data (void *value)
 261 {
 262   /* Call the backend */
 263   return __gthread_objc_thread_set_data (value);
 264 }
 265
 266 /*
 267   Returns the thread's local storage pointer.  Returns NULL on failure.
 268   */
 269 void *
 270 objc_thread_get_data (void)
 271 {
 272   /* Call the backend */
 273   return __gthread_objc_thread_get_data ();
 274 }
 275
 276 /* Frontend mutex functions */
 277
 278 /*
 279   Allocate a mutex.  Return the mutex pointer if successful or NULL if the
 280   allocation failed for any reason.
 281   */
 282 objc_mutex_t
 283 objc_mutex_allocate (void)
 284 {
 285   objc_mutex_t mutex;
 286
 287   /* Allocate the mutex structure */
 288   if (! (mutex = (objc_mutex_t)objc_malloc (sizeof (struct objc_mutex))))
 289     return NULL;
 290
 291   /* Call backend to create the mutex */
 292   if (__gthread_objc_mutex_allocate (mutex))
 293     {
 294       /* failed! */
 295       objc_free (mutex);
 296       return NULL;
 297     }
 298
 299   /* Initialize mutex */
 300   mutex->owner = NULL;
 301   mutex->depth = 0;
 302   return mutex;
 303 }
 304
 305 /*
 306   Deallocate a mutex.  Note that this includes an implicit mutex_lock to
 307   insure that no one else is using the lock.  It is legal to deallocate
 308   a lock if we have a lock on it, but illegal to deallocate a lock held
 309   by anyone else.
 310   Returns the number of locks on the thread.  (1 for deallocate).
 311   */
 312 int
 313 objc_mutex_deallocate (objc_mutex_t mutex)
 314 {
 315   int depth;
 316
 317   /* Valid mutex? */
 318   if (! mutex)
 319     return -1;
 320
 321   /* Acquire lock on mutex */
 322   depth = objc_mutex_lock (mutex);
 323
 324   /* Call backend to destroy mutex */
 325   if (__gthread_objc_mutex_deallocate (mutex))
 326     return -1;
 327
 328   /* Free the mutex structure */
 329   objc_free (mutex);
 330
 331   /* Return last depth */
 332   return depth;
 333 }
 334
 335 /*
 336   Grab a lock on a mutex.  If this thread already has a lock on this mutex
 337   then we increment the lock count.  If another thread has a lock on the
 338   mutex we block and wait for the thread to release the lock.
 339   Returns the lock count on the mutex held by this thread.
 340   */
 341 int
 342 objc_mutex_lock (objc_mutex_t mutex)
 343 {
 344   objc_thread_t thread_id;
 345   int status;
 346
 347   /* Valid mutex? */
 348   if (! mutex)
 349     return -1;
 350
 351   /* If we already own the lock then increment depth */
 352   thread_id = __gthread_objc_thread_id ();
 353   if (mutex->owner == thread_id)
 354     return ++mutex->depth;
 355
 356   /* Call the backend to lock the mutex */
 357   status = __gthread_objc_mutex_lock (mutex);
 358
 359   /* Failed? */
 360   if (status)
 361     return status;
 362
 363   /* Successfully locked the thread */
 364   mutex->owner = thread_id;
 365   return mutex->depth = 1;
 366 }
 367
 368 /*
 369   Try to grab a lock on a mutex.  If this thread already has a lock on
 370   this mutex then we increment the lock count and return it.  If another
 371   thread has a lock on the mutex returns -1.
 372   */
 373 int
 374 objc_mutex_trylock (objc_mutex_t mutex)
 375 {
 376   objc_thread_t thread_id;
 377   int status;
 378
 379   /* Valid mutex? */
 380   if (! mutex)
 381     return -1;
 382
 383   /* If we already own the lock then increment depth */
 384   thread_id = __gthread_objc_thread_id ();
 385   if (mutex->owner == thread_id)
 386     return ++mutex->depth;
 387
 388   /* Call the backend to try to lock the mutex */
 389   status = __gthread_objc_mutex_trylock (mutex);
 390
 391   /* Failed? */
 392   if (status)
 393     return status;
 394
 395   /* Successfully locked the thread */
 396   mutex->owner = thread_id;
 397   return mutex->depth = 1;
 398 }
 399
 400 /*
 401   Unlocks the mutex by one level.
 402   Decrements the lock count on this mutex by one.
 403   If the lock count reaches zero, release the lock on the mutex.
 404   Returns the lock count on the mutex.
 405   It is an error to attempt to unlock a mutex which this thread
 406   doesn't hold in which case return -1 and the mutex is unaffected.
 407   */
 408 int
 409 objc_mutex_unlock (objc_mutex_t mutex)
 410 {
 411   objc_thread_t thread_id;
 412   int status;
 413
 414   /* Valid mutex? */
 415   if (! mutex)
 416     return -1;
 417
 418   /* If another thread owns the lock then abort */
 419   thread_id = __gthread_objc_thread_id ();
 420   if (mutex->owner != thread_id)
 421     return -1;
 422
 423   /* Decrement depth and return */
 424   if (mutex->depth > 1)
 425     return --mutex->depth;
 426
 427   /* Depth down to zero so we are no longer the owner */
 428   mutex->depth = 0;
 429   mutex->owner = NULL;
 430
 431   /* Have the backend unlock the mutex */
 432   status = __gthread_objc_mutex_unlock (mutex);
 433
 434   /* Failed? */
 435   if (status)
 436     return status;
 437
 438   return 0;
 439 }
 440
 441 /* Frontend condition mutex functions */
 442
 443 /*
 444   Allocate a condition.  Return the condition pointer if successful or NULL
 445   if the allocation failed for any reason.
 446   */
 447 objc_condition_t
 448 objc_condition_allocate (void)
 449 {
 450   objc_condition_t condition;
 451
 452   /* Allocate the condition mutex structure */
 453   if (! (condition =
 454          (objc_condition_t) objc_malloc (sizeof (struct objc_condition))))
 455     return NULL;
 456
 457   /* Call the backend to create the condition mutex */
 458   if (__gthread_objc_condition_allocate (condition))
 459     {
 460       /* failed! */
 461       objc_free (condition);
 462       return NULL;
 463     }
 464
 465   /* Success! */
 466   return condition;
 467 }
 468
 469 /*
 470   Deallocate a condition. Note that this includes an implicit
 471   condition_broadcast to insure that waiting threads have the opportunity
 472   to wake.  It is legal to dealloc a condition only if no other
 473   thread is/will be using it. Here we do NOT check for other threads
 474   waiting but just wake them up.
 475   */
 476 int
 477 objc_condition_deallocate (objc_condition_t condition)
 478 {
 479   /* Broadcast the condition */
 480   if (objc_condition_broadcast (condition))
 481     return -1;
 482
 483   /* Call the backend to destroy */
 484   if (__gthread_objc_condition_deallocate (condition))
 485     return -1;
 486
 487   /* Free the condition mutex structure */
 488   objc_free (condition);
 489
 490   return 0;
 491 }
 492
 493 /*
 494   Wait on the condition unlocking the mutex until objc_condition_signal ()
 495   or objc_condition_broadcast () are called for the same condition. The
 496   given mutex *must* have the depth set to 1 so that it can be unlocked
 497   here, so that someone else can lock it and signal/broadcast the condition.
 498   The mutex is used to lock access to the shared data that make up the
 499   "condition" predicate.
 500   */
 501 int
 502 objc_condition_wait (objc_condition_t condition, objc_mutex_t mutex)
 503 {
 504   objc_thread_t thread_id;
 505
 506   /* Valid arguments? */
 507   if (! mutex || ! condition)
 508     return -1;
 509
 510   /* Make sure we are owner of mutex */
 511   thread_id = __gthread_objc_thread_id ();
 512   if (mutex->owner != thread_id)
 513     return -1;
 514
 515   /* Cannot be locked more than once */
 516   if (mutex->depth > 1)
 517     return -1;
 518
 519   /* Virtually unlock the mutex */
 520   mutex->depth = 0;
 521   mutex->owner = (objc_thread_t)NULL;
 522
 523   /* Call the backend to wait */
 524   __gthread_objc_condition_wait (condition, mutex);
 525
 526   /* Make ourselves owner of the mutex */
 527   mutex->owner = thread_id;
 528   mutex->depth = 1;
 529
 530   return 0;
 531 }
 532
 533 /*
 534   Wake up all threads waiting on this condition. It is recommended that
 535   the called would lock the same mutex as the threads in objc_condition_wait
 536   before changing the "condition predicate" and make this call and unlock it
 537   right away after this call.
 538   */
 539 int
 540 objc_condition_broadcast (objc_condition_t condition)
 541 {
 542   /* Valid condition mutex? */
 543   if (! condition)
 544     return -1;
 545
 546   return __gthread_objc_condition_broadcast (condition);
 547 }
 548
 549 /*
 550   Wake up one thread waiting on this condition. It is recommended that
 551   the called would lock the same mutex as the threads in objc_condition_wait
 552   before changing the "condition predicate" and make this call and unlock it
 553   right away after this call.
 554   */
 555 int
 556 objc_condition_signal (objc_condition_t condition)
 557 {
 558   /* Valid condition mutex? */
 559   if (! condition)
 560     return -1;
 561
 562   return __gthread_objc_condition_signal (condition);
 563 }
 564
 565 /* Make the objc thread system aware that a thread which is managed
 566    (started, stopped) by external code could access objc facilities
 567    from now on.  This is used when you are interfacing with some
 568    external non-objc-based environment/system - you must call
 569    objc_thread_add () before an alien thread makes any calls to
 570    Objective-C.  Do not cause the _objc_became_multi_threaded hook to
 571    be executed. */
 572 void
 573 objc_thread_add (void)
 574 {
 575   objc_mutex_lock (__objc_runtime_mutex);
 576   __objc_is_multi_threaded = 1;
 577   __objc_runtime_threads_alive++;
 578   objc_mutex_unlock (__objc_runtime_mutex);
 579 }
 580
 581 /* Make the objc thread system aware that a thread managed (started,
 582    stopped) by some external code will no longer access objc and thus
 583    can be forgotten by the objc thread system.  Call
 584    objc_thread_remove () when your alien thread is done with making
 585    calls to Objective-C. */
 586 void
 587 objc_thread_remove (void)
 588 {
 589   objc_mutex_lock (__objc_runtime_mutex);
 590   __objc_runtime_threads_alive--;
 591   objc_mutex_unlock (__objc_runtime_mutex);
 592 }
 593
 594 /* End of File */