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/message.h" /* For objc_msg_lookup().  */
  42 #include "objc/runtime.h"
  43 #include "objc-private/module-abi-8.h"
  44 #include "objc-private/runtime.h"
  45 #include <gthr.h>
  46
  47 #include <stdlib.h>
  48
  49 /* Global exit status. */
  50 int __objc_thread_exit_status = 0;
  51
  52 /* Flag which lets us know if we ever became multi threaded.  */
  53 int __objc_is_multi_threaded = 0;
  54
  55 /* The hook function called when the runtime becomes multi
  56    threaded.  */
  57 objc_thread_callback _objc_became_multi_threaded = NULL;
  58
  59 /* Use this to set the hook function that will be called when the
  60    runtime initially becomes multi threaded.  The hook function is
  61    only called once, meaning only when the 2nd thread is spawned, not
  62    for each and every thread.
  63
  64    It returns the previous hook function or NULL if there is none.
  65
  66    A program outside of the runtime could set this to some function so
  67    it can be informed; for example, the GNUstep Base Library sets it
  68    so it can implement the NSBecomingMultiThreaded notification.  */
  69 objc_thread_callback objc_set_thread_callback (objc_thread_callback func)
  70 {
  71   objc_thread_callback temp = _objc_became_multi_threaded;
  72   _objc_became_multi_threaded = func;
  73   return temp;
  74 }
  75
  76 /* Private functions.
  77
  78    These functions are utilized by the runtime, but they are not
  79    considered part of the public interface.  */
  80
  81 /* Initialize the threads subsystem.  */
  82 int
  83 __objc_init_thread_system(void)
  84 {
  85   return __gthread_objc_init_thread_system ();
  86 }
  87
  88 /* First function called in a thread, starts everything else.
  89
  90    This function is passed to the backend by objc_thread_detach as the
  91    starting function for a new thread.  */
  92 struct __objc_thread_start_state
  93 {
  94   SEL selector;
  95   id object;
  96   id argument;
  97 };
  98
  99 static void __attribute__((noreturn))
 100 __objc_thread_detach_function (struct __objc_thread_start_state *istate)
 101 {
 102   /* Valid state? */
 103   if (istate)
 104     {
 105       id (*imp) (id, SEL, id);
 106       SEL selector = istate->selector;
 107       id object   = istate->object;
 108       id argument = istate->argument;
 109
 110       /* Don't need anymore so free it.  */
 111       objc_free (istate);
 112
 113       /* Clear out the thread local storage.  */
 114       objc_thread_set_data (NULL);
 115
 116       /* Check to see if we just became multi threaded. */
 117       if (! __objc_is_multi_threaded)
 118         {
 119           __objc_is_multi_threaded = 1;
 120
 121           /* Call the hook function.  */
 122           if (_objc_became_multi_threaded != NULL)
 123             (*_objc_became_multi_threaded) ();
 124         }
 125
 126       /* Call the method.  */
 127       if ((imp = (id (*) (id, SEL, id))objc_msg_lookup (object, selector)))
 128         (*imp) (object, selector, argument);
 129       else
 130         {
 131           /* FIXME: Should we abort here ? */
 132           _objc_abort ("objc_thread_detach called with bad selector.\n");
 133         }
 134     }
 135   else
 136     {
 137       /* FIXME: Should we abort here ? */
 138       _objc_abort ("objc_thread_detach called with NULL state.\n");
 139     }
 140
 141   /* Exit the thread.  */
 142   objc_thread_exit ();
 143
 144   /* Make sure compiler detects no return.  */
 145   __builtin_trap ();
 146 }
 147
 148 /* Public functions.
 149
 150    These functions constitute the public interface to the Objective-C
 151    thread and mutex functionality.  */
 152
 153 /* Detach a new thread of execution and return its id.  Returns NULL
 154    if fails.  Thread is started by sending message with selector to
 155    object.  Message takes a single argument.  */
 156 objc_thread_t
 157 objc_thread_detach (SEL selector, id object, id argument)
 158 {
 159   struct __objc_thread_start_state *istate;
 160   objc_thread_t        thread_id = NULL;
 161
 162   /* Allocate the state structure.  */
 163   if (!(istate = (struct __objc_thread_start_state *)objc_malloc
 164         (sizeof (*istate))))
 165     return NULL;
 166
 167   /* Initialize the state structure.  */
 168   istate->selector = selector;
 169   istate->object = object;
 170   istate->argument = argument;
 171
 172   /* Lock access.  */
 173   objc_mutex_lock (__objc_runtime_mutex);
 174
 175   /* Call the backend to spawn the thread.  */
 176   if ((thread_id = __gthread_objc_thread_detach ((void *)__objc_thread_detach_function,
 177                                                  istate)) == NULL)
 178     {
 179       /* Failed!  */
 180       objc_mutex_unlock (__objc_runtime_mutex);
 181       objc_free (istate);
 182       return NULL;
 183     }
 184
 185   /* Increment our thread counter.  */
 186   __objc_runtime_threads_alive++;
 187   objc_mutex_unlock (__objc_runtime_mutex);
 188
 189   return thread_id;
 190 }
 191
 192 /* Set the current thread's priority.  */
 193 int
 194 objc_thread_set_priority (int priority)
 195 {
 196   return __gthread_objc_thread_set_priority (priority);
 197 }
 198
 199 /* Return the current thread's priority.  */
 200 int
 201 objc_thread_get_priority (void)
 202 {
 203   return __gthread_objc_thread_get_priority ();
 204 }
 205
 206 /* Yield our process time to another thread.  Any BUSY waiting that is
 207    done by a thread should use this function to make sure that other
 208    threads can make progress even on a lazy uniprocessor system.  */
 209 void
 210 objc_thread_yield (void)
 211 {
 212   __gthread_objc_thread_yield ();
 213 }
 214
 215 /* Terminate the current tread.  Doesn't return.  Actually, if it
 216    failed returns -1.  */
 217 int
 218 objc_thread_exit (void)
 219 {
 220   /* Decrement our counter of the number of threads alive.  */
 221   objc_mutex_lock (__objc_runtime_mutex);
 222   __objc_runtime_threads_alive--;
 223   objc_mutex_unlock (__objc_runtime_mutex);
 224
 225   /* Call the backend to terminate the thread.  */
 226   return __gthread_objc_thread_exit ();
 227 }
 228
 229 /* Returns an integer value which uniquely describes a thread.  Must
 230    not be NULL which is reserved as a marker for "no thread".  */
 231 objc_thread_t
 232 objc_thread_id (void)
 233 {
 234   return __gthread_objc_thread_id ();
 235 }
 236
 237 /* Sets the thread's local storage pointer.  Returns 0 if successful
 238    or -1 if failed.  */
 239 int
 240 objc_thread_set_data (void *value)
 241 {
 242   return __gthread_objc_thread_set_data (value);
 243 }
 244
 245 /* Returns the thread's local storage pointer.  Returns NULL on
 246    failure.  */
 247 void *
 248 objc_thread_get_data (void)
 249 {
 250   return __gthread_objc_thread_get_data ();
 251 }
 252
 253 /* Public mutex functions */
 254
 255 /* Allocate a mutex.  Return the mutex pointer if successful or NULL
 256    if the allocation failed for any reason.  */
 257 objc_mutex_t
 258 objc_mutex_allocate (void)
 259 {
 260   objc_mutex_t mutex;
 261
 262   /* Allocate the mutex structure.  */
 263   if (! (mutex = (objc_mutex_t)objc_malloc (sizeof (struct objc_mutex))))
 264     return NULL;
 265
 266   /* Call backend to create the mutex.  */
 267   if (__gthread_objc_mutex_allocate (mutex))
 268     {
 269       /* Failed!  */
 270       objc_free (mutex);
 271       return NULL;
 272     }
 273
 274   /* Initialize mutex.  */
 275   mutex->owner = NULL;
 276   mutex->depth = 0;
 277   return mutex;
 278 }
 279
 280 /* Deallocate a mutex.  Note that this includes an implicit mutex_lock
 281    to insure that no one else is using the lock.  It is legal to
 282    deallocate a lock if we have a lock on it, but illegal to
 283    deallocate a lock held by anyone else.  Returns the number of locks
 284    on the thread.  (1 for deallocate).  */
 285 int
 286 objc_mutex_deallocate (objc_mutex_t mutex)
 287 {
 288   int depth;
 289
 290   /* Valid mutex?  */
 291   if (! mutex)
 292     return -1;
 293
 294   /* Acquire lock on mutex.  */
 295   depth = objc_mutex_lock (mutex);
 296
 297   /* Call backend to destroy mutex.  */
 298   if (__gthread_objc_mutex_deallocate (mutex))
 299     return -1;
 300
 301   /* Free the mutex structure.  */
 302   objc_free (mutex);
 303
 304   /* Return last depth.  */
 305   return depth;
 306 }
 307
 308 /* Grab a lock on a mutex.  If this thread already has a lock on this
 309    mutex then we increment the lock count.  If another thread has a
 310    lock on the mutex we block and wait for the thread to release the
 311    lock.  Returns the lock count on the mutex held by this thread.  */
 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 = __gthread_objc_thread_id ();
 324   if (mutex->owner == thread_id)
 325     return ++mutex->depth;
 326
 327   /* Call the backend to lock the mutex.  */
 328   status = __gthread_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 /* Try to grab a lock on a mutex.  If this thread already has a lock
 340    on this mutex then we increment the lock count and return it.  If
 341    another thread has a lock on the mutex returns -1.  */
 342 int
 343 objc_mutex_trylock (objc_mutex_t mutex)
 344 {
 345   objc_thread_t thread_id;
 346   int status;
 347
 348   /* Valid mutex?  */
 349   if (! mutex)
 350     return -1;
 351
 352   /* If we already own the lock then increment depth.  */
 353   thread_id = __gthread_objc_thread_id ();
 354   if (mutex->owner == thread_id)
 355     return ++mutex->depth;
 356
 357   /* Call the backend to try to lock the mutex.  */
 358   status = __gthread_objc_mutex_trylock (mutex);
 359
 360   /* Failed?  */
 361   if (status)
 362     return status;
 363
 364   /* Successfully locked the thread.  */
 365   mutex->owner = thread_id;
 366   return mutex->depth = 1;
 367 }
 368
 369 /* Unlocks the mutex by one level.  Decrements the lock count on this
 370    mutex by one.  If the lock count reaches zero, release the lock on
 371    the mutex.  Returns the lock count on the mutex.  It is an error to
 372    attempt to unlock a mutex which this thread doesn't hold in which
 373    case return -1 and the mutex is unaffected.  */
 374 int
 375 objc_mutex_unlock (objc_mutex_t mutex)
 376 {
 377   objc_thread_t thread_id;
 378   int status;
 379
 380   /* Valid mutex?  */
 381   if (! mutex)
 382     return -1;
 383
 384   /* If another thread owns the lock then abort.  */
 385   thread_id = __gthread_objc_thread_id ();
 386   if (mutex->owner != thread_id)
 387     return -1;
 388
 389   /* Decrement depth and return.  */
 390   if (mutex->depth > 1)
 391     return --mutex->depth;
 392
 393   /* Depth down to zero so we are no longer the owner.  */
 394   mutex->depth = 0;
 395   mutex->owner = NULL;
 396
 397   /* Have the backend unlock the mutex.  */
 398   status = __gthread_objc_mutex_unlock (mutex);
 399
 400   /* Failed?  */
 401   if (status)
 402     return status;
 403
 404   return 0;
 405 }
 406
 407 /* Public condition mutex functions */
 408
 409 /* Allocate a condition.  Return the condition pointer if successful
 410    or NULL if the allocation failed for any reason.  */
 411 objc_condition_t
 412 objc_condition_allocate (void)
 413 {
 414   objc_condition_t condition;
 415
 416   /* Allocate the condition mutex structure.  */
 417   if (! (condition =
 418          (objc_condition_t) objc_malloc (sizeof (struct objc_condition))))
 419     return NULL;
 420
 421   /* Call the backend to create the condition mutex.  */
 422   if (__gthread_objc_condition_allocate (condition))
 423     {
 424       /* Failed!  */
 425       objc_free (condition);
 426       return NULL;
 427     }
 428
 429   /* Success!  */
 430   return condition;
 431 }
 432
 433 /* Deallocate a condition. Note that this includes an implicit
 434    condition_broadcast to insure that waiting threads have the
 435    opportunity to wake.  It is legal to dealloc a condition only if no
 436    other thread is/will be using it. Here we do NOT check for other
 437    threads waiting but just wake them up.  */
 438 int
 439 objc_condition_deallocate (objc_condition_t condition)
 440 {
 441   /* Broadcast the condition.  */
 442   if (objc_condition_broadcast (condition))
 443     return -1;
 444
 445   /* Call the backend to destroy.  */
 446   if (__gthread_objc_condition_deallocate (condition))
 447     return -1;
 448
 449   /* Free the condition mutex structure.  */
 450   objc_free (condition);
 451
 452   return 0;
 453 }
 454
 455 /* Wait on the condition unlocking the mutex until
 456    objc_condition_signal () or objc_condition_broadcast () are called
 457    for the same condition. The given mutex *must* have the depth set
 458    to 1 so that it can be unlocked here, so that someone else can lock
 459    it and signal/broadcast the condition.  The mutex is used to lock
 460    access to the shared data that make up the "condition"
 461    predicate.  */
 462 int
 463 objc_condition_wait (objc_condition_t condition, objc_mutex_t mutex)
 464 {
 465   objc_thread_t thread_id;
 466
 467   /* Valid arguments?  */
 468   if (! mutex || ! condition)
 469     return -1;
 470
 471   /* Make sure we are owner of mutex.  */
 472   thread_id = __gthread_objc_thread_id ();
 473   if (mutex->owner != thread_id)
 474     return -1;
 475
 476   /* Cannot be locked more than once.  */
 477   if (mutex->depth > 1)
 478     return -1;
 479
 480   /* Virtually unlock the mutex.  */
 481   mutex->depth = 0;
 482   mutex->owner = (objc_thread_t)NULL;
 483
 484   /* Call the backend to wait.  */
 485   __gthread_objc_condition_wait (condition, mutex);
 486
 487   /* Make ourselves owner of the mutex.  */
 488   mutex->owner = thread_id;
 489   mutex->depth = 1;
 490
 491   return 0;
 492 }
 493
 494 /* Wake up all threads waiting on this condition. It is recommended
 495    that the called would lock the same mutex as the threads in
 496    objc_condition_wait before changing the "condition predicate" and
 497    make this call and unlock it right away after this call.  */
 498 int
 499 objc_condition_broadcast (objc_condition_t condition)
 500 {
 501   /* Valid condition mutex?  */
 502   if (! condition)
 503     return -1;
 504
 505   return __gthread_objc_condition_broadcast (condition);
 506 }
 507
 508 /* Wake up one thread waiting on this condition. It is recommended
 509    that the called would lock the same mutex as the threads in
 510    objc_condition_wait before changing the "condition predicate" and
 511    make this call and unlock it right away after this call.  */
 512 int
 513 objc_condition_signal (objc_condition_t condition)
 514 {
 515   /* Valid condition mutex?  */
 516   if (! condition)
 517     return -1;
 518
 519   return __gthread_objc_condition_signal (condition);
 520 }
 521
 522 /* Make the objc thread system aware that a thread which is managed
 523    (started, stopped) by external code could access objc facilities
 524    from now on.  This is used when you are interfacing with some
 525    external non-objc-based environment/system - you must call
 526    objc_thread_add () before an alien thread makes any calls to
 527    Objective-C.  Do not cause the _objc_became_multi_threaded hook to
 528    be executed. */
 529 void
 530 objc_thread_add (void)
 531 {
 532   objc_mutex_lock (__objc_runtime_mutex);
 533   __objc_is_multi_threaded = 1;
 534   __objc_runtime_threads_alive++;
 535   objc_mutex_unlock (__objc_runtime_mutex);
 536 }
 537
 538 /* Make the objc thread system aware that a thread managed (started,
 539    stopped) by some external code will no longer access objc and thus
 540    can be forgotten by the objc thread system.  Call
 541    objc_thread_remove () when your alien thread is done with making
 542    calls to Objective-C. */
 543 void
 544 objc_thread_remove (void)
 545 {
 546   objc_mutex_lock (__objc_runtime_mutex);
 547   __objc_runtime_threads_alive--;
 548   objc_mutex_unlock (__objc_runtime_mutex);
 549 }
 550