libobjc/thr.c

   1 /* GNU Objective C Runtime Thread Interface
   2    Copyright (C) 1996-2021 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 #include "config.h"
  29 #include "tconfig.h"
  30 #include "coretypes.h"
  31 #include "tm.h"
  32 #include "defaults.h"
  33 #include "objc/thr.h"
  34 #include "objc/message.h" /* For objc_msg_lookup().  */
  35 #include "objc/runtime.h"
  36 #include "objc-private/module-abi-8.h"
  37 #include "objc-private/runtime.h"
  38 #include <gthr.h>
  39
  40 #include <stdlib.h>
  41
  42 /* Global exit status. */
  43 int __objc_thread_exit_status = 0;
  44
  45 /* Flag which lets us know if we ever became multi threaded.  */
  46 int __objc_is_multi_threaded = 0;
  47
  48 /* The hook function called when the runtime becomes multi
  49    threaded.  */
  50 objc_thread_callback _objc_became_multi_threaded = NULL;
  51
  52 /* Use this to set the hook function that will be called when the
  53    runtime initially becomes multi threaded.  The hook function is
  54    only called once, meaning only when the 2nd thread is spawned, not
  55    for each and every thread.
  56
  57    It returns the previous hook function or NULL if there is none.
  58
  59    A program outside of the runtime could set this to some function so
  60    it can be informed; for example, the GNUstep Base Library sets it
  61    so it can implement the NSBecomingMultiThreaded notification.  */
  62 objc_thread_callback objc_set_thread_callback (objc_thread_callback func)
  63 {
  64   objc_thread_callback temp = _objc_became_multi_threaded;
  65   _objc_became_multi_threaded = func;
  66   return temp;
  67 }
  68
  69 /* Private functions.
  70
  71    These functions are utilized by the runtime, but they are not
  72    considered part of the public interface.  */
  73
  74 /* Initialize the threads subsystem.  */
  75 int
  76 __objc_init_thread_system(void)
  77 {
  78   return __gthread_objc_init_thread_system ();
  79 }
  80
  81 /* First function called in a thread, starts everything else.
  82
  83    This function is passed to the backend by objc_thread_detach as the
  84    starting function for a new thread.  */
  85 struct __objc_thread_start_state
  86 {
  87   SEL selector;
  88   id object;
  89   id argument;
  90 };
  91
  92 static void __attribute__((noreturn))
  93 __objc_thread_detach_function (struct __objc_thread_start_state *istate)
  94 {
  95   /* Valid state? */
  96   if (istate)
  97     {
  98       id (*imp) (id, SEL, id);
  99       SEL selector = istate->selector;
 100       id object   = istate->object;
 101       id argument = istate->argument;
 102
 103       /* Don't need anymore so free it.  */
 104       objc_free (istate);
 105
 106       /* Clear out the thread local storage.  */
 107       objc_thread_set_data (NULL);
 108
 109       /* Check to see if we just became multi threaded. */
 110       if (! __objc_is_multi_threaded)
 111         {
 112           __objc_is_multi_threaded = 1;
 113
 114           /* Call the hook function.  */
 115           if (_objc_became_multi_threaded != NULL)
 116             (*_objc_became_multi_threaded) ();
 117         }
 118
 119       /* Call the method.  */
 120       if ((imp = (id (*) (id, SEL, id))objc_msg_lookup (object, selector)))
 121         (*imp) (object, selector, argument);
 122       else
 123         {
 124           /* FIXME: Should we abort here ? */
 125           _objc_abort ("objc_thread_detach called with bad selector.\n");
 126         }
 127     }
 128   else
 129     {
 130       /* FIXME: Should we abort here ? */
 131       _objc_abort ("objc_thread_detach called with NULL state.\n");
 132     }
 133
 134   /* Exit the thread.  */
 135   objc_thread_exit ();
 136
 137   /* Make sure compiler detects no return.  */
 138   __builtin_trap ();
 139 }
 140
 141 /* Public functions.
 142
 143    These functions constitute the public interface to the Objective-C
 144    thread and mutex functionality.  */
 145
 146 /* Detach a new thread of execution and return its id.  Returns NULL
 147    if fails.  Thread is started by sending message with selector to
 148    object.  Message takes a single argument.  */
 149 objc_thread_t
 150 objc_thread_detach (SEL selector, id object, id argument)
 151 {
 152   struct __objc_thread_start_state *istate;
 153   objc_thread_t        thread_id = NULL;
 154
 155   /* Allocate the state structure.  */
 156   if (!(istate = (struct __objc_thread_start_state *)objc_malloc
 157         (sizeof (*istate))))
 158     return NULL;
 159
 160   /* Initialize the state structure.  */
 161   istate->selector = selector;
 162   istate->object = object;
 163   istate->argument = argument;
 164
 165   /* Lock access.  */
 166   objc_mutex_lock (__objc_runtime_mutex);
 167
 168   /* Call the backend to spawn the thread.  */
 169   if ((thread_id = __gthread_objc_thread_detach ((void *)__objc_thread_detach_function,
 170                                                  istate)) == NULL)
 171     {
 172       /* Failed!  */
 173       objc_mutex_unlock (__objc_runtime_mutex);
 174       objc_free (istate);
 175       return NULL;
 176     }
 177
 178   /* Increment our thread counter.  */
 179   __objc_runtime_threads_alive++;
 180   objc_mutex_unlock (__objc_runtime_mutex);
 181
 182   return thread_id;
 183 }
 184
 185 /* Set the current thread's priority.  */
 186 int
 187 objc_thread_set_priority (int priority)
 188 {
 189   return __gthread_objc_thread_set_priority (priority);
 190 }
 191
 192 /* Return the current thread's priority.  */
 193 int
 194 objc_thread_get_priority (void)
 195 {
 196   return __gthread_objc_thread_get_priority ();
 197 }
 198
 199 /* Yield our process time to another thread.  Any BUSY waiting that is
 200    done by a thread should use this function to make sure that other
 201    threads can make progress even on a lazy uniprocessor system.  */
 202 void
 203 objc_thread_yield (void)
 204 {
 205   __gthread_objc_thread_yield ();
 206 }
 207
 208 /* Terminate the current tread.  Doesn't return.  Actually, if it
 209    failed returns -1.  */
 210 int
 211 objc_thread_exit (void)
 212 {
 213   /* Decrement our counter of the number of threads alive.  */
 214   objc_mutex_lock (__objc_runtime_mutex);
 215   __objc_runtime_threads_alive--;
 216   objc_mutex_unlock (__objc_runtime_mutex);
 217
 218   /* Call the backend to terminate the thread.  */
 219   return __gthread_objc_thread_exit ();
 220 }
 221
 222 /* Returns an integer value which uniquely describes a thread.  Must
 223    not be NULL which is reserved as a marker for "no thread".  */
 224 objc_thread_t
 225 objc_thread_id (void)
 226 {
 227   return __gthread_objc_thread_id ();
 228 }
 229
 230 /* Sets the thread's local storage pointer.  Returns 0 if successful
 231    or -1 if failed.  */
 232 int
 233 objc_thread_set_data (void *value)
 234 {
 235   return __gthread_objc_thread_set_data (value);
 236 }
 237
 238 /* Returns the thread's local storage pointer.  Returns NULL on
 239    failure.  */
 240 void *
 241 objc_thread_get_data (void)
 242 {
 243   return __gthread_objc_thread_get_data ();
 244 }
 245
 246 /* Public mutex functions */
 247
 248 /* Allocate a mutex.  Return the mutex pointer if successful or NULL
 249    if the allocation failed for any reason.  */
 250 objc_mutex_t
 251 objc_mutex_allocate (void)
 252 {
 253   objc_mutex_t mutex;
 254
 255   /* Allocate the mutex structure.  */
 256   if (! (mutex = (objc_mutex_t)objc_malloc (sizeof (struct objc_mutex))))
 257     return NULL;
 258
 259   /* Call backend to create the mutex.  */
 260   if (__gthread_objc_mutex_allocate (mutex))
 261     {
 262       /* Failed!  */
 263       objc_free (mutex);
 264       return NULL;
 265     }
 266
 267   /* Initialize mutex.  */
 268   mutex->owner = NULL;
 269   mutex->depth = 0;
 270   return mutex;
 271 }
 272
 273 /* Deallocate a mutex.  Note that this includes an implicit mutex_lock
 274    to insure that no one else is using the lock.  It is legal to
 275    deallocate a lock if we have a lock on it, but illegal to
 276    deallocate a lock held by anyone else.  Returns the number of locks
 277    on the thread.  (1 for deallocate).  */
 278 int
 279 objc_mutex_deallocate (objc_mutex_t mutex)
 280 {
 281   int depth;
 282
 283   /* Valid mutex?  */
 284   if (! mutex)
 285     return -1;
 286
 287   /* Acquire lock on mutex.  */
 288   depth = objc_mutex_lock (mutex);
 289
 290   /* Call backend to destroy mutex.  */
 291   if (__gthread_objc_mutex_deallocate (mutex))
 292     return -1;
 293
 294   /* Free the mutex structure.  */
 295   objc_free (mutex);
 296
 297   /* Return last depth.  */
 298   return depth;
 299 }
 300
 301 /* Grab a lock on a mutex.  If this thread already has a lock on this
 302    mutex then we increment the lock count.  If another thread has a
 303    lock on the mutex we block and wait for the thread to release the
 304    lock.  Returns the lock count on the mutex held by this thread.  */
 305 int
 306 objc_mutex_lock (objc_mutex_t mutex)
 307 {
 308   objc_thread_t thread_id;
 309   int status;
 310
 311   /* Valid mutex?  */
 312   if (! mutex)
 313     return -1;
 314
 315   /* If we already own the lock then increment depth.  */
 316   thread_id = __gthread_objc_thread_id ();
 317   if (mutex->owner == thread_id)
 318     return ++mutex->depth;
 319
 320   /* Call the backend to lock the mutex.  */
 321   status = __gthread_objc_mutex_lock (mutex);
 322
 323   /* Failed?  */
 324   if (status)
 325     return status;
 326
 327   /* Successfully locked the thread.  */
 328   mutex->owner = thread_id;
 329   return mutex->depth = 1;
 330 }
 331
 332 /* Try to grab a lock on a mutex.  If this thread already has a lock
 333    on this mutex then we increment the lock count and return it.  If
 334    another thread has a lock on the mutex returns -1.  */
 335 int
 336 objc_mutex_trylock (objc_mutex_t mutex)
 337 {
 338   objc_thread_t thread_id;
 339   int status;
 340
 341   /* Valid mutex?  */
 342   if (! mutex)
 343     return -1;
 344
 345   /* If we already own the lock then increment depth.  */
 346   thread_id = __gthread_objc_thread_id ();
 347   if (mutex->owner == thread_id)
 348     return ++mutex->depth;
 349
 350   /* Call the backend to try to lock the mutex.  */
 351   status = __gthread_objc_mutex_trylock (mutex);
 352
 353   /* Failed?  */
 354   if (status)
 355     return status;
 356
 357   /* Successfully locked the thread.  */
 358   mutex->owner = thread_id;
 359   return mutex->depth = 1;
 360 }
 361
 362 /* Unlocks the mutex by one level.  Decrements the lock count on this
 363    mutex by one.  If the lock count reaches zero, release the lock on
 364    the mutex.  Returns the lock count on the mutex.  It is an error to
 365    attempt to unlock a mutex which this thread doesn't hold in which
 366    case return -1 and the mutex is unaffected.  */
 367 int
 368 objc_mutex_unlock (objc_mutex_t mutex)
 369 {
 370   objc_thread_t thread_id;
 371   int status;
 372
 373   /* Valid mutex?  */
 374   if (! mutex)
 375     return -1;
 376
 377   /* If another thread owns the lock then abort.  */
 378   thread_id = __gthread_objc_thread_id ();
 379   if (mutex->owner != thread_id)
 380     return -1;
 381
 382   /* Decrement depth and return.  */
 383   if (mutex->depth > 1)
 384     return --mutex->depth;
 385
 386   /* Depth down to zero so we are no longer the owner.  */
 387   mutex->depth = 0;
 388   mutex->owner = NULL;
 389
 390   /* Have the backend unlock the mutex.  */
 391   status = __gthread_objc_mutex_unlock (mutex);
 392
 393   /* Failed?  */
 394   if (status)
 395     return status;
 396
 397   return 0;
 398 }
 399
 400 /* Public condition mutex functions */
 401
 402 /* Allocate a condition.  Return the condition pointer if successful
 403    or NULL if the allocation failed for any reason.  */
 404 objc_condition_t
 405 objc_condition_allocate (void)
 406 {
 407   objc_condition_t condition;
 408
 409   /* Allocate the condition mutex structure.  */
 410   if (! (condition =
 411          (objc_condition_t) objc_malloc (sizeof (struct objc_condition))))
 412     return NULL;
 413
 414   /* Call the backend to create the condition mutex.  */
 415   if (__gthread_objc_condition_allocate (condition))
 416     {
 417       /* Failed!  */
 418       objc_free (condition);
 419       return NULL;
 420     }
 421
 422   /* Success!  */
 423   return condition;
 424 }
 425
 426 /* Deallocate a condition. Note that this includes an implicit
 427    condition_broadcast to insure that waiting threads have the
 428    opportunity to wake.  It is legal to dealloc a condition only if no
 429    other thread is/will be using it. Here we do NOT check for other
 430    threads waiting but just wake them up.  */
 431 int
 432 objc_condition_deallocate (objc_condition_t condition)
 433 {
 434   /* Broadcast the condition.  */
 435   if (objc_condition_broadcast (condition))
 436     return -1;
 437
 438   /* Call the backend to destroy.  */
 439   if (__gthread_objc_condition_deallocate (condition))
 440     return -1;
 441
 442   /* Free the condition mutex structure.  */
 443   objc_free (condition);
 444
 445   return 0;
 446 }
 447
 448 /* Wait on the condition unlocking the mutex until
 449    objc_condition_signal () or objc_condition_broadcast () are called
 450    for the same condition. The given mutex *must* have the depth set
 451    to 1 so that it can be unlocked here, so that someone else can lock
 452    it and signal/broadcast the condition.  The mutex is used to lock
 453    access to the shared data that make up the "condition"
 454    predicate.  */
 455 int
 456 objc_condition_wait (objc_condition_t condition, objc_mutex_t mutex)
 457 {
 458   objc_thread_t thread_id;
 459
 460   /* Valid arguments?  */
 461   if (! mutex || ! condition)
 462     return -1;
 463
 464   /* Make sure we are owner of mutex.  */
 465   thread_id = __gthread_objc_thread_id ();
 466   if (mutex->owner != thread_id)
 467     return -1;
 468
 469   /* Cannot be locked more than once.  */
 470   if (mutex->depth > 1)
 471     return -1;
 472
 473   /* Virtually unlock the mutex.  */
 474   mutex->depth = 0;
 475   mutex->owner = (objc_thread_t)NULL;
 476
 477   /* Call the backend to wait.  */
 478   __gthread_objc_condition_wait (condition, mutex);
 479
 480   /* Make ourselves owner of the mutex.  */
 481   mutex->owner = thread_id;
 482   mutex->depth = 1;
 483
 484   return 0;
 485 }
 486
 487 /* Wake up all threads waiting on this condition. It is recommended
 488    that the called would lock the same mutex as the threads in
 489    objc_condition_wait before changing the "condition predicate" and
 490    make this call and unlock it right away after this call.  */
 491 int
 492 objc_condition_broadcast (objc_condition_t condition)
 493 {
 494   /* Valid condition mutex?  */
 495   if (! condition)
 496     return -1;
 497
 498   return __gthread_objc_condition_broadcast (condition);
 499 }
 500
 501 /* Wake up one thread waiting on this condition. It is recommended
 502    that the called would lock the same mutex as the threads in
 503    objc_condition_wait before changing the "condition predicate" and
 504    make this call and unlock it right away after this call.  */
 505 int
 506 objc_condition_signal (objc_condition_t condition)
 507 {
 508   /* Valid condition mutex?  */
 509   if (! condition)
 510     return -1;
 511
 512   return __gthread_objc_condition_signal (condition);
 513 }
 514
 515 /* Make the objc thread system aware that a thread which is managed
 516    (started, stopped) by external code could access objc facilities
 517    from now on.  This is used when you are interfacing with some
 518    external non-objc-based environment/system - you must call
 519    objc_thread_add () before an alien thread makes any calls to
 520    Objective-C.  Do not cause the _objc_became_multi_threaded hook to
 521    be executed. */
 522 void
 523 objc_thread_add (void)
 524 {
 525   objc_mutex_lock (__objc_runtime_mutex);
 526   __objc_is_multi_threaded = 1;
 527   __objc_runtime_threads_alive++;
 528   objc_mutex_unlock (__objc_runtime_mutex);
 529 }
 530
 531 /* Make the objc thread system aware that a thread managed (started,
 532    stopped) by some external code will no longer access objc and thus
 533    can be forgotten by the objc thread system.  Call
 534    objc_thread_remove () when your alien thread is done with making
 535    calls to Objective-C. */
 536 void
 537 objc_thread_remove (void)
 538 {
 539   objc_mutex_lock (__objc_runtime_mutex);
 540   __objc_runtime_threads_alive--;
 541   objc_mutex_unlock (__objc_runtime_mutex);
 542 }
 543