Unix/Linux/sheepthreads.c

/*
 *  sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
 *                   like nonstandard stacks)
 *
 *  SheepShaver (C) 1997-2002 Christian Bauer and Marc Hellwig
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

/*
 *  NOTES:
 *   - pthread_cancel() kills the thread immediately
 *   - Semaphores are VERY restricted: the only supported use is to have one
 *     thread sem_wait() on the semaphore while other threads sem_post() it
 *     (i.e. to use the semaphore as a signal)
 */

#include <sys/types.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <sched.h>
#include <pthread.h>
#include <semaphore.h>


/* Thread stack size */
#define STACK_SIZE 65536

/* From asm_linux.S */
extern int atomic_add(int *var, int add);
extern int atomic_and(int *var, int and);
extern int atomic_or(int *var, int or);
extern int test_and_set(int *var, int val);

/* Linux kernel calls */
extern int __clone(int (*fn)(void *), void *, int, void *);

/* struct sem_t */
#define status __status
#define spinlock __spinlock
#define sem_lock __sem_lock
#define sem_value __sem_value
#define sem_waiting __sem_waiting


/*
 *  Return pthread ID of self
 */

pthread_t pthread_self(void)
{
        return getpid();
}


/*
 *  Test whether two pthread IDs are equal
 */

int pthread_equal(pthread_t t1, pthread_t t2)
{
        return t1 == t2;
}


/*
 *  Send signal to thread
 */

int pthread_kill(pthread_t thread, int sig)
{
        if (kill(thread, sig) == -1)
                return errno;
        else
                return 0;
}


/*
 *  Create pthread
 */

struct new_thread {
        void *(*fn)(void *);
        void *arg;
};

static int start_thread(void *arg)
{
        struct new_thread *nt = (struct new_thread *)arg;
        nt->fn(nt->arg);
        return 0;
}

int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine)(void *), void *arg)
{
        struct new_thread *nt;
        void *stack;
        int pid;

        nt = (struct new_thread *)malloc(sizeof(struct new_thread));
        nt->fn = start_routine;
        nt->arg = arg;
        stack = malloc(STACK_SIZE);

        pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM | CLONE_FS | CLONE_FILES, nt);
        if (pid == -1) {
                free(stack);
                free(nt);
                return errno;
        } else {
                *thread = pid;
                return 0;
        }
}


/*
 *  Join pthread
 */

int pthread_join(pthread_t thread, void **ret)
{
        do {
                if (waitpid(thread, NULL, 0) >= 0)
                        break;
        } while (errno == EINTR);
        if (ret)
                *ret = NULL;
        return 0;
}


/*
 *  Cancel thread
 */

int pthread_cancel(pthread_t thread)
{
        kill(thread, SIGINT);
        return 0;
}


/*
 *  Test for cancellation
 */

void pthread_testcancel(void)
{
}


/*
 *  Spinlocks
 */

static int try_acquire_spinlock(int *lock)
{
        return test_and_set(lock, 1) == 0;
}

static void acquire_spinlock(volatile int *lock)
{
        do {
                while (*lock) ;
        } while (test_and_set((int *)lock, 1) != 0);
}

static void release_spinlock(int *lock)
{
        *lock = 0;
}


/*
 *  Initialize mutex
 */

int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *mutex_attr)
{
        // pthread_init_lock
        mutex->__m_lock.__status = 0;
        mutex->__m_lock.__spinlock = 0;

        mutex->__m_kind = mutex_attr ? mutex_attr->__mutexkind : PTHREAD_MUTEX_TIMED_NP;
        mutex->__m_count = 0;
        mutex->__m_owner = NULL;
        return 0;
}


/*
 *  Destroy mutex
 */

int pthread_mutex_destroy(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                return (mutex->__m_lock.__status != 0) ? EBUSY : 0;
        default:
                return EINVAL;
        }
}


/*
 *  Lock mutex
 */

int pthread_mutex_lock(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                acquire_spinlock(&mutex->__m_lock.__spinlock);
                return 0;
        default:
                return EINVAL;
        }
}


/*
 *  Try to lock mutex
 */

int pthread_mutex_trylock(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                if (!try_acquire_spinlock(&mutex->__m_lock.__spinlock))
                        return EBUSY;
                return 0;
        default:
                return EINVAL;
        }
}


/*
 *  Unlock mutex
 */

int pthread_mutex_unlock(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                release_spinlock(&mutex->__m_lock.__spinlock);
                return 0;
        default:
                return EINVAL;
        }
}


/*
 *  Create mutex attribute
 */

int pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
        attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
        return 0;
}


/*
 *  Destroy mutex attribute
 */

int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
{
        return 0;
}


/*
 *  Init semaphore
 */

int sem_init(sem_t *sem, int pshared, unsigned int value)
{
        sem->sem_lock.status = 0;
        sem->sem_lock.spinlock = 0;
        sem->sem_value = value;
        sem->sem_waiting = NULL;
        return 0;
}


/*
 *  Delete remaphore
 */

int sem_destroy(sem_t *sem)
{
        return 0;
}


/*
 *  Wait on semaphore
 */

void null_handler(int sig)
{
}

int sem_wait(sem_t *sem)
{
        acquire_spinlock(&sem->sem_lock.spinlock);
        if (atomic_add((int *)&sem->sem_value, -1) >= 0) {
                sigset_t mask;
                if (!sem->sem_lock.status) {
                        struct sigaction sa;
                        sem->sem_lock.status = SIGUSR2;
                        sa.sa_handler = null_handler;
                        sa.sa_flags = SA_RESTART;
                        sigemptyset(&sa.sa_mask);
                        sigaction(sem->sem_lock.status, &sa, NULL);
                }
                sem->sem_waiting = (struct _pthread_descr_struct *)getpid();
                sigemptyset(&mask);
                sigsuspend(&mask);
                sem->sem_waiting = NULL;
        }
        release_spinlock(&sem->sem_lock.spinlock);
        return 0;
}


/*
 *  Post semaphore
 */

int sem_post(sem_t *sem)
{
        acquire_spinlock(&sem->sem_lock.spinlock);
        atomic_add((int *)&sem->sem_value, 1);
        if (sem->sem_waiting)
                kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
        release_spinlock(&sem->sem_lock.spinlock);
        return 0;
}
Revision:	1.3
Committed:	2004-01-04T06:55:50Z (20 years, 10 months ago) by gbeauche
Content type:	text/plain
Branch:	MAIN
Changes since 1.2:	+107 -0 lines
Log Message:	Light implementation of pthread_mutexes
#	Content
1	/*
2	* sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
3	* like nonstandard stacks)
4	*
5	* SheepShaver (C) 1997-2002 Christian Bauer and Marc Hellwig
6	*
7	* This program is free software; you can redistribute it and/or modify
8	* it under the terms of the GNU General Public License as published by
9	* the Free Software Foundation; either version 2 of the License, or
10	* (at your option) any later version.
11	*
12	* This program is distributed in the hope that it will be useful,
13	* but WITHOUT ANY WARRANTY; without even the implied warranty of
14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15	* GNU General Public License for more details.
16	*
17	* You should have received a copy of the GNU General Public License
18	* along with this program; if not, write to the Free Software
19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
20	*/
21
22	/*
23	* NOTES:
24	* - pthread_cancel() kills the thread immediately
25	* - Semaphores are VERY restricted: the only supported use is to have one
26	* thread sem_wait() on the semaphore while other threads sem_post() it
27	* (i.e. to use the semaphore as a signal)
28	*/
29
30	#include <sys/types.h>
31	#include <sys/wait.h>
32	#include <stdlib.h>
33	#include <errno.h>
34	#include <unistd.h>
35	#include <signal.h>
36	#include <sched.h>
37	#include <pthread.h>
38	#include <semaphore.h>
39
40
41	/* Thread stack size */
42	#define STACK_SIZE 65536
43
44	/* From asm_linux.S */
45	extern int atomic_add(int *var, int add);
46	extern int atomic_and(int *var, int and);
47	extern int atomic_or(int *var, int or);
48	extern int test_and_set(int *var, int val);
49
50	/* Linux kernel calls */
51	extern int __clone(int (fn)(void ), void , int, void );
52
53	/* struct sem_t */
54	#define status __status
55	#define spinlock __spinlock
56	#define sem_lock __sem_lock
57	#define sem_value __sem_value
58	#define sem_waiting __sem_waiting
59
60
61	/*
62	* Return pthread ID of self
63	*/
64
65	pthread_t pthread_self(void)
66	{
67	return getpid();
68	}
69
70
71	/*
72	* Test whether two pthread IDs are equal
73	*/
74
75	int pthread_equal(pthread_t t1, pthread_t t2)
76	{
77	return t1 == t2;
78	}
79
80
81	/*
82	* Send signal to thread
83	*/
84
85	int pthread_kill(pthread_t thread, int sig)
86	{
87	if (kill(thread, sig) == -1)
88	return errno;
89	else
90	return 0;
91	}
92
93
94	/*
95	* Create pthread
96	*/
97
98	struct new_thread {
99	void (fn)(void *);
100	void *arg;
101	};
102
103	static int start_thread(void *arg)
104	{
105	struct new_thread nt = (struct new_thread )arg;
106	nt->fn(nt->arg);
107	return 0;
108	}
109
110	int pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg)
111	{
112	struct new_thread *nt;
113	void *stack;
114	int pid;
115
116	nt = (struct new_thread *)malloc(sizeof(struct new_thread));
117	nt->fn = start_routine;
118	nt->arg = arg;
119	stack = malloc(STACK_SIZE);
120
121	pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM \| CLONE_FS \| CLONE_FILES, nt);
122	if (pid == -1) {
123	free(stack);
124	free(nt);
125	return errno;
126	} else {
127	*thread = pid;
128	return 0;
129	}
130	}
131
132
133	/*
134	* Join pthread
135	*/
136
137	int pthread_join(pthread_t thread, void **ret)
138	{
139	do {
140	if (waitpid(thread, NULL, 0) >= 0)
141	break;
142	} while (errno == EINTR);
143	if (ret)
144	*ret = NULL;
145	return 0;
146	}
147
148
149	/*
150	* Cancel thread
151	*/
152
153	int pthread_cancel(pthread_t thread)
154	{
155	kill(thread, SIGINT);
156	return 0;
157	}
158
159
160	/*
161	* Test for cancellation
162	*/
163
164	void pthread_testcancel(void)
165	{
166	}
167
168
169	/*
170	* Spinlocks
171	*/
172
173	static int try_acquire_spinlock(int *lock)
174	{
175	return test_and_set(lock, 1) == 0;
176	}
177
178	static void acquire_spinlock(volatile int *lock)
179	{
180	do {
181	while (*lock) ;
182	} while (test_and_set((int *)lock, 1) != 0);
183	}
184
185	static void release_spinlock(int *lock)
186	{
187	*lock = 0;
188	}
189
190
191	/*
192	* Initialize mutex
193	*/
194
195	int pthread_mutex_init(pthread_mutex_t mutex, const pthread_mutexattr_t mutex_attr)
196	{
197	// pthread_init_lock
198	mutex->__m_lock.__status = 0;
199	mutex->__m_lock.__spinlock = 0;
200
201	mutex->__m_kind = mutex_attr ? mutex_attr->__mutexkind : PTHREAD_MUTEX_TIMED_NP;
202	mutex->__m_count = 0;
203	mutex->__m_owner = NULL;
204	return 0;
205	}
206
207
208	/*
209	* Destroy mutex
210	*/
211
212	int pthread_mutex_destroy(pthread_mutex_t *mutex)
213	{
214	switch (mutex->__m_kind) {
215	case PTHREAD_MUTEX_TIMED_NP:
216	return (mutex->__m_lock.__status != 0) ? EBUSY : 0;
217	default:
218	return EINVAL;
219	}
220	}
221
222
223	/*
224	* Lock mutex
225	*/
226
227	int pthread_mutex_lock(pthread_mutex_t *mutex)
228	{
229	switch (mutex->__m_kind) {
230	case PTHREAD_MUTEX_TIMED_NP:
231	acquire_spinlock(&mutex->__m_lock.__spinlock);
232	return 0;
233	default:
234	return EINVAL;
235	}
236	}
237
238
239	/*
240	* Try to lock mutex
241	*/
242
243	int pthread_mutex_trylock(pthread_mutex_t *mutex)
244	{
245	switch (mutex->__m_kind) {
246	case PTHREAD_MUTEX_TIMED_NP:
247	if (!try_acquire_spinlock(&mutex->__m_lock.__spinlock))
248	return EBUSY;
249	return 0;
250	default:
251	return EINVAL;
252	}
253	}
254
255
256	/*
257	* Unlock mutex
258	*/
259
260	int pthread_mutex_unlock(pthread_mutex_t *mutex)
261	{
262	switch (mutex->__m_kind) {
263	case PTHREAD_MUTEX_TIMED_NP:
264	release_spinlock(&mutex->__m_lock.__spinlock);
265	return 0;
266	default:
267	return EINVAL;
268	}
269	}
270
271
272	/*
273	* Create mutex attribute
274	*/
275
276	int pthread_mutexattr_init(pthread_mutexattr_t *attr)
277	{
278	attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
279	return 0;
280	}
281
282
283	/*
284	* Destroy mutex attribute
285	*/
286
287	int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
288	{
289	return 0;
290	}
291
292
293	/*
294	* Init semaphore
295	*/
296
297	int sem_init(sem_t *sem, int pshared, unsigned int value)
298	{
299	sem->sem_lock.status = 0;
300	sem->sem_lock.spinlock = 0;
301	sem->sem_value = value;
302	sem->sem_waiting = NULL;
303	return 0;
304	}
305
306
307	/*
308	* Delete remaphore
309	*/
310
311	int sem_destroy(sem_t *sem)
312	{
313	return 0;
314	}
315
316
317	/*
318	* Wait on semaphore
319	*/
320
321	void null_handler(int sig)
322	{
323	}
324
325	int sem_wait(sem_t *sem)
326	{
327	acquire_spinlock(&sem->sem_lock.spinlock);
328	if (atomic_add((int *)&sem->sem_value, -1) >= 0) {
329	sigset_t mask;
330	if (!sem->sem_lock.status) {
331	struct sigaction sa;
332	sem->sem_lock.status = SIGUSR2;
333	sa.sa_handler = null_handler;
334	sa.sa_flags = SA_RESTART;
335	sigemptyset(&sa.sa_mask);
336	sigaction(sem->sem_lock.status, &sa, NULL);
337	}
338	sem->sem_waiting = (struct _pthread_descr_struct *)getpid();
339	sigemptyset(&mask);
340	sigsuspend(&mask);
341	sem->sem_waiting = NULL;
342	}
343	release_spinlock(&sem->sem_lock.spinlock);
344	return 0;
345	}
346
347
348	/*
349	* Post semaphore
350	*/
351
352	int sem_post(sem_t *sem)
353	{
354	acquire_spinlock(&sem->sem_lock.spinlock);
355	atomic_add((int *)&sem->sem_value, 1);
356	if (sem->sem_waiting)
357	kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
358	release_spinlock(&sem->sem_lock.spinlock);
359	return 0;
360	}