1 /* GNU Objective C Runtime Thread Implementation
2 Copyright (C) 1996 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. */
28 * This structure represents a single mutual exclusion lock. Lock semantics
29 * are detailed with the subsequent functions. We use whatever lock is
30 * provided by the system. We augment it with depth and current owner id
31 * fields to implement and re-entrant lock.
35 volatile _objc_thread_t owner; /* Id of thread that owns. */
36 volatile int depth; /* # of acquires. */
40 * Initialize the threads subsystem. Returns 0 if successful, or -1 if no
41 * thread support is available.
44 __objc_init_thread_system(void)
46 DEBUG_PRINTF("__objc_init_thread_system\n");
47 return -1; /* Failed. */
51 * Create a new thread of execution and return its id. Return NULL if fails.
52 * The new thread starts in "func" with the given argument.
55 objc_thread_create(void (*func)(void *arg), void *arg)
57 return NULL; /* We can't start threads. */
61 * Set the current thread's priority.
64 objc_thread_set_priority(int priority)
66 return -1; /* Failed. */
70 * Return the current thread's priority.
73 objc_thread_get_priority(void)
75 return OBJC_THREAD_INTERACTIVE_PRIORITY; /* Highest priority. */
79 * Yield our process time to another thread. Any BUSY waiting that is done
80 * by a thread should use this function to make sure that other threads can
81 * make progress even on a lazy uniprocessor system.
84 objc_thread_yield(void)
90 * Terminate the current tread. Doesn't return anything. Doesn't return.
91 * Actually, if it failed returns -1.
94 objc_thread_exit(void)
96 exit(__objc_thread_exit_status);
101 * Returns an integer value which uniquely describes a thread. Must not be
102 * NULL which is reserved as a marker for "no thread".
107 return (_objc_thread_t)1; /* No thread support, use 1.*/
111 * Sets the thread's local storage pointer. Returns 0 if successful or -1
115 static void *thread_local_storage = NULL;
118 objc_thread_set_data(void *value)
120 thread_local_storage = value;
125 * Returns the thread's local storage pointer. Returns NULL on failure.
128 objc_thread_get_data(void)
130 return thread_local_storage;
134 * Allocate a mutex. Return the mutex pointer if successful or NULL if the
135 * allocation failed for any reason.
138 objc_mutex_allocate(void)
142 if (!(mutex = (_objc_mutex_t)__objc_xmalloc(sizeof(struct _objc_mutex))))
143 return NULL; /* Abort if malloc failed. */
145 mutex->owner = NULL; /* No owner. */
146 mutex->depth = 0; /* No locks. */
147 return mutex; /* Return mutex handle. */
151 * Deallocate a mutex. Note that this includes an implicit mutex_lock to
152 * insure that no one else is using the lock. It is legal to deallocate
153 * a lock if we have a lock on it, but illegal to deallocate a lock held
155 * Returns the number of locks on the thread. (1 for deallocate).
158 objc_mutex_deallocate(_objc_mutex_t mutex)
160 int depth; /* # of locks on mutex. */
162 if (!mutex) /* Is argument bad? */
163 return -1; /* Yes, abort. */
164 depth = objc_mutex_lock(mutex); /* Must have lock. */
166 free(mutex); /* Free memory. */
167 return depth; /* Return last depth. */
171 * Grab a lock on a mutex. If this thread already has a lock on this mutex
172 * then we increment the lock count. If another thread has a lock on the
173 * mutex we block and wait for the thread to release the lock.
174 * Returns the lock count on the mutex held by this thread.
177 objc_mutex_lock(_objc_mutex_t mutex)
179 _objc_thread_t thread_id; /* Cache our thread id. */
181 if (!mutex) /* Is argument bad? */
182 return -1; /* Yes, abort. */
183 thread_id = objc_thread_id(); /* Get this thread's id. */
184 if (mutex->owner == thread_id) /* Already own lock? */
185 return ++mutex->depth; /* Yes, increment depth. */
187 mutex->owner = thread_id; /* Mark thread as owner. */
189 return mutex->depth = 1; /* Increment depth to end. */
193 * Try to grab a lock on a mutex. If this thread already has a lock on
194 * this mutex then we increment the lock count and return it. If another
195 * thread has a lock on the mutex returns -1.
198 objc_mutex_trylock(_objc_mutex_t mutex)
200 _objc_thread_t thread_id; /* Cache our thread id. */
202 if (!mutex) /* Is argument bad? */
203 return -1; /* Yes, abort. */
204 thread_id = objc_thread_id(); /* Get this thread's id. */
205 if (mutex->owner == thread_id) /* Already own lock? */
206 return ++mutex->depth; /* Yes, increment depth. */
208 mutex->owner = thread_id; /* Mark thread as owner. */
209 return mutex->depth = 1; /* Increment depth to end. */
213 * Decrements the lock count on this mutex by one. If the lock count reaches
214 * zero, release the lock on the mutex. Returns the lock count on the mutex.
215 * It is an error to attempt to unlock a mutex which this thread doesn't hold
216 * in which case return -1 and the mutex is unaffected.
217 * Will also return -1 if the mutex free fails.
220 objc_mutex_unlock(_objc_mutex_t mutex)
222 _objc_thread_t thread_id; /* Cache our thread id. */
224 if (!mutex) /* Is argument bad? */
225 return -1; /* Yes, abort. */
226 thread_id = objc_thread_id(); /* Get this thread's id. */
227 if (mutex->owner != thread_id) /* Does some else own lock? */
228 return -1; /* Yes, abort. */
229 if (mutex->depth > 1) /* Released last lock? */
230 return --mutex->depth; /* No, Decrement depth, end.*/
231 mutex->depth = 0; /* Yes, reset depth to 0. */
232 mutex->owner = NULL; /* Set owner to "no thread".*/
234 return 0; /* No, return success. */