1 /* GNU Objective C Runtime Thread Implementation
2 Copyright (C) 1996, 1997 Free Software Foundation, Inc.
3 Contributed by Galen C. Hunt (gchunt@cs.rochester.edu)
5 This file is part of GNU CC.
7 GNU CC 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 2, or (at your option) any later version.
11 GNU CC 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
16 You should have received a copy of the GNU General Public License along with
17 GNU CC; see the file COPYING. If not, write to the Free Software
18 Foundation, 59 Temple Place - Suite 330,
19 Boston, MA 02111-1307, USA. */
21 /* As a special exception, if you link this library with files compiled with
22 GCC to produce an executable, this does not cause the resulting executable
23 to be covered by the GNU General Public License. This exception does not
24 however invalidate any other reasons why the executable file might be
25 covered by the GNU General Public License. */
31 * This structure represents a single mutual exclusion lock. Lock semantics
32 * are detailed with the subsequent functions. We use whatever lock is
33 * provided by the system. We augment it with depth and current owner id
34 * fields to implement and re-entrant lock.
38 volatile objc_thread_t owner; /* Id of thread that owns. */
39 volatile int depth; /* # of acquires. */
43 * Initialize the threads subsystem. Returns 0 if successful, or -1 if no
44 * thread support is available.
47 __objc_init_thread_system(void)
49 DEBUG_PRINTF("__objc_init_thread_system\n");
50 return -1; /* Failed. */
54 * Create a new thread of execution and return its id. Return NULL if fails.
55 * The new thread starts in "func" with the given argument.
58 objc_thread_create(void (*func)(void *arg), void *arg)
60 return NULL; /* We can't start threads. */
64 * Set the current thread's priority.
67 objc_thread_set_priority(int priority)
69 return -1; /* Failed. */
73 * Return the current thread's priority.
76 objc_thread_get_priority(void)
78 return OBJC_THREAD_INTERACTIVE_PRIORITY; /* Highest priority. */
82 * Yield our process time to another thread. Any BUSY waiting that is done
83 * by a thread should use this function to make sure that other threads can
84 * make progress even on a lazy uniprocessor system.
87 objc_thread_yield(void)
93 * Terminate the current tread. Doesn't return anything. Doesn't return.
94 * Actually, if it failed returns -1.
97 objc_thread_exit(void)
99 exit(__objc_thread_exit_status);
104 * Returns an integer value which uniquely describes a thread. Must not be
105 * NULL which is reserved as a marker for "no thread".
110 return (objc_thread_t)1; /* No thread support, use 1.*/
114 * Sets the thread's local storage pointer. Returns 0 if successful or -1
118 static void *thread_local_storage = NULL;
121 objc_thread_set_data(void *value)
123 thread_local_storage = value;
128 * Returns the thread's local storage pointer. Returns NULL on failure.
131 objc_thread_get_data(void)
133 return thread_local_storage;
137 * Allocate a mutex. Return the mutex pointer if successful or NULL if the
138 * allocation failed for any reason.
141 objc_mutex_allocate(void)
145 if (!(mutex = (objc_mutex_t)objc_malloc(sizeof(struct objc_mutex))))
146 return NULL; /* Abort if malloc failed. */
148 mutex->owner = NULL; /* No owner. */
149 mutex->depth = 0; /* No locks. */
150 return mutex; /* Return mutex handle. */
154 * Deallocate a mutex. Note that this includes an implicit mutex_lock to
155 * insure that no one else is using the lock. It is legal to deallocate
156 * a lock if we have a lock on it, but illegal to deallocate a lock held
158 * Returns the number of locks on the thread. (1 for deallocate).
161 objc_mutex_deallocate(objc_mutex_t mutex)
163 int depth; /* # of locks on mutex. */
165 if (!mutex) /* Is argument bad? */
166 return -1; /* Yes, abort. */
167 depth = objc_mutex_lock(mutex); /* Must have lock. */
169 objc_free(mutex); /* Free memory. */
170 return depth; /* Return last depth. */
174 * Grab a lock on a mutex. If this thread already has a lock on this mutex
175 * then we increment the lock count. If another thread has a lock on the
176 * mutex we block and wait for the thread to release the lock.
177 * Returns the lock count on the mutex held by this thread.
180 objc_mutex_lock(objc_mutex_t mutex)
182 objc_thread_t thread_id; /* Cache our thread id. */
184 if (!mutex) /* Is argument bad? */
185 return -1; /* Yes, abort. */
186 thread_id = objc_thread_id(); /* Get this thread's id. */
187 if (mutex->owner == thread_id) /* Already own lock? */
188 return ++mutex->depth; /* Yes, increment depth. */
190 mutex->owner = thread_id; /* Mark thread as owner. */
192 return mutex->depth = 1; /* Increment depth to end. */
196 * Try to grab a lock on a mutex. If this thread already has a lock on
197 * this mutex then we increment the lock count and return it. If another
198 * thread has a lock on the mutex returns -1.
201 objc_mutex_trylock(objc_mutex_t mutex)
203 objc_thread_t thread_id; /* Cache our thread id. */
205 if (!mutex) /* Is argument bad? */
206 return -1; /* Yes, abort. */
207 thread_id = objc_thread_id(); /* Get this thread's id. */
208 if (mutex->owner == thread_id) /* Already own lock? */
209 return ++mutex->depth; /* Yes, increment depth. */
211 mutex->owner = thread_id; /* Mark thread as owner. */
212 return mutex->depth = 1; /* Increment depth to end. */
216 * Decrements the lock count on this mutex by one. If the lock count reaches
217 * zero, release the lock on the mutex. Returns the lock count on the mutex.
218 * It is an error to attempt to unlock a mutex which this thread doesn't hold
219 * in which case return -1 and the mutex is unaffected.
220 * Will also return -1 if the mutex free fails.
223 objc_mutex_unlock(objc_mutex_t mutex)
225 objc_thread_t thread_id; /* Cache our thread id. */
227 if (!mutex) /* Is argument bad? */
228 return -1; /* Yes, abort. */
229 thread_id = objc_thread_id(); /* Get this thread's id. */
230 if (mutex->owner != thread_id) /* Does some else own lock? */
231 return -1; /* Yes, abort. */
232 if (mutex->depth > 1) /* Released last lock? */
233 return --mutex->depth; /* No, Decrement depth, end.*/
234 mutex->depth = 0; /* Yes, reset depth to 0. */
235 mutex->owner = NULL; /* Set owner to "no thread".*/
237 return 0; /* No, return success. */