Unix/Linux/sheepthreads.c

/*
 *  sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
 *                   like nonstandard stacks)
 *
 *  SheepShaver (C) 1997-2005 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 <pthread.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 */
typedef struct {
        struct _pthread_fastlock __sem_lock;
        int __sem_value;
        _pthread_descr __sem_waiting;
} sem_t;

#define SEM_VALUE_MAX 64
#define status __status
#define spinlock __spinlock
#define sem_lock __sem_lock
#define sem_value __sem_value
#define sem_waiting __sem_waiting

/* Wait for "clone" children only (Linux 2.4+ specific) */
#ifndef __WCLONE
#define __WCLONE 0
#endif


/*
 *  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, __WCLONE) >= 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
 */

/* For multiprocessor systems, we want to ensure all memory accesses
   are completed before we reset a lock.  On other systems, we still
   need to make sure that the compiler has flushed everything to memory.  */
#define MEMORY_BARRIER() __asm__ __volatile__ ("sync" : : : "memory")

static void fastlock_init(struct _pthread_fastlock *lock)
{
        lock->status = 0;
        lock->spinlock = 0;
}

static int fastlock_try_acquire(struct _pthread_fastlock *lock)
{
        int res = EBUSY;
        if (test_and_set(&lock->spinlock, 1) == 0) {
                if (lock->status == 0) {
                        lock->status = 1;
                        MEMORY_BARRIER();
                        res = 0;
                }
                lock->spinlock = 0;
        }
        return res;
}

static void fastlock_acquire(struct _pthread_fastlock *lock)
{
        MEMORY_BARRIER();
        while (test_and_set(&lock->spinlock, 1))
                usleep(0);
}

static void fastlock_release(struct _pthread_fastlock *lock)
{
        MEMORY_BARRIER();
        lock->spinlock = 0;
        __asm__ __volatile__ ("" : "=m" (lock->spinlock) : "m" (lock->spinlock));
}


/*
 *  Initialize mutex
 */

int pthread_mutex_init(pthread_mutex_t *mutex, const pthread_mutexattr_t *mutex_attr)
{
        fastlock_init(&mutex->__m_lock);
        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:
                fastlock_acquire(&mutex->__m_lock);
                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:
                return fastlock_try_acquire(&mutex->__m_lock);
        default:
                return EINVAL;
        }
}


/*
 *  Unlock mutex
 */

int pthread_mutex_unlock(pthread_mutex_t *mutex)
{
        switch (mutex->__m_kind) {
        case PTHREAD_MUTEX_TIMED_NP:
                fastlock_release(&mutex->__m_lock);
                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)
{
        if (sem == NULL || value > SEM_VALUE_MAX) {
                errno = EINVAL;
                return -1;
        }
        if (pshared) {
                errno = ENOSYS;
                return -1;
        }
        fastlock_init(&sem->sem_lock);
        sem->sem_value = value;
        sem->sem_waiting = NULL;
        return 0;
}


/*
 *  Delete remaphore
 */

int sem_destroy(sem_t *sem)
{
        if (sem == NULL) {
                errno = EINVAL;
                return -1;
        }
        if (sem->sem_waiting) {
                errno = EBUSY;
                return -1;
        }
        sem->sem_value = 0;
        sem->sem_waiting = NULL;
        return 0;
}


/*
 *  Wait on semaphore
 */

int sem_wait(sem_t *sem)
{
        if (sem == NULL) {
                errno = EINVAL;
                return -1;
        }
        fastlock_acquire(&sem->sem_lock);
        if (sem->sem_value > 0) {
                sem->sem_value--;
                fastlock_release(&sem->sem_lock);
                return 0;
        }
        sem->sem_waiting = (struct _pthread_descr_struct *)((long)sem->sem_waiting + 1);
        while (sem->sem_value == 0) {
                fastlock_release(&sem->sem_lock);
                usleep(0);
                fastlock_acquire(&sem->sem_lock);
        }
        sem->sem_value--;
        fastlock_release(&sem->sem_lock);
        return 0;
}


/*
 *  Post semaphore
 */

int sem_post(sem_t *sem)
{
        if (sem == NULL) {
                errno = EINVAL;
                return -1;
        }
        fastlock_acquire(&sem->sem_lock);
        if (sem->sem_waiting)
                sem->sem_waiting = (struct _pthread_descr_struct *)((long)sem->sem_waiting - 1);
        else {
                if (sem->sem_value >= SEM_VALUE_MAX) {
                        errno = ERANGE;
                        fastlock_release(&sem->sem_lock);
                        return -1;
                }
        }
        sem->sem_value++;
        fastlock_release(&sem->sem_lock);
        return 0;
}


/*
 *  Simple producer/consumer test program
 */

#ifdef TEST
#include <stdio.h>

static sem_t p_sem, c_sem;
static int data = 0;

static void *producer_func(void *arg)
{
        int i, n = (int)arg;
        for (i = 0; i < n; i++) {
                sem_wait(&p_sem);
                data++;
                sem_post(&c_sem);
        }
        return NULL;
}

static void *consumer_func(void *arg)
{
        int i, n = (int)arg;
        for (i = 0; i < n; i++) {
                sem_wait(&c_sem);
                printf("data: %d\n", data);
                sem_post(&p_sem);
        }
        sleep(1); // for testing pthread_join()
        return NULL;
}

int main(void)
{
        pthread_t producer_thread, consumer_thread;
        static const int N = 5;

        if (sem_init(&c_sem, 0, 0) < 0)
                return 1;
        if (sem_init(&p_sem, 0, 1) < 0)
                return 2;
        if (pthread_create(&producer_thread, NULL, producer_func, (void *)N) != 0)
                return 3;
        if (pthread_create(&consumer_thread, NULL, consumer_func, (void *)N) != 0)
                return 4;
        pthread_join(producer_thread, NULL);
        pthread_join(consumer_thread, NULL);
        sem_destroy(&p_sem);
        sem_destroy(&c_sem);
        if (data != N)
                return 5;
        return 0;
}
#endif
Revision:	1.9
Committed:	2005-07-03T23:28:30Z (19 years, 4 months ago) by gbeauche
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.8:	+7 -1 lines
Log Message:	Don't use sem_t definition from our local "semaphore.h" layer. Copy the definitions from original LinuxThreads.
#	Content
1	/*
2	* sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
3	* like nonstandard stacks)
4	*
5	* SheepShaver (C) 1997-2005 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 <pthread.h>
37
38
39	/* Thread stack size */
40	#define STACK_SIZE 65536
41
42	/* From asm_linux.S */
43	extern int atomic_add(int *var, int add);
44	extern int atomic_and(int *var, int and);
45	extern int atomic_or(int *var, int or);
46	extern int test_and_set(int *var, int val);
47
48	/* Linux kernel calls */
49	extern int __clone(int (fn)(void ), void , int, void );
50
51	/* struct sem_t */
52	typedef struct {
53	struct _pthread_fastlock __sem_lock;
54	int __sem_value;
55	_pthread_descr __sem_waiting;
56	} sem_t;
57
58	#define SEM_VALUE_MAX 64
59	#define status __status
60	#define spinlock __spinlock
61	#define sem_lock __sem_lock
62	#define sem_value __sem_value
63	#define sem_waiting __sem_waiting
64
65	/* Wait for "clone" children only (Linux 2.4+ specific) */
66	#ifndef __WCLONE
67	#define __WCLONE 0
68	#endif
69
70
71	/*
72	* Return pthread ID of self
73	*/
74
75	pthread_t pthread_self(void)
76	{
77	return getpid();
78	}
79
80
81	/*
82	* Test whether two pthread IDs are equal
83	*/
84
85	int pthread_equal(pthread_t t1, pthread_t t2)
86	{
87	return t1 == t2;
88	}
89
90
91	/*
92	* Send signal to thread
93	*/
94
95	int pthread_kill(pthread_t thread, int sig)
96	{
97	if (kill(thread, sig) == -1)
98	return errno;
99	else
100	return 0;
101	}
102
103
104	/*
105	* Create pthread
106	*/
107
108	struct new_thread {
109	void (fn)(void *);
110	void *arg;
111	};
112
113	static int start_thread(void *arg)
114	{
115	struct new_thread nt = (struct new_thread )arg;
116	nt->fn(nt->arg);
117	return 0;
118	}
119
120	int pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg)
121	{
122	struct new_thread *nt;
123	void *stack;
124	int pid;
125
126	nt = (struct new_thread *)malloc(sizeof(struct new_thread));
127	nt->fn = start_routine;
128	nt->arg = arg;
129	stack = malloc(STACK_SIZE);
130
131	pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM \| CLONE_FS \| CLONE_FILES, nt);
132	if (pid == -1) {
133	free(stack);
134	free(nt);
135	return errno;
136	} else {
137	*thread = pid;
138	return 0;
139	}
140	}
141
142
143	/*
144	* Join pthread
145	*/
146
147	int pthread_join(pthread_t thread, void **ret)
148	{
149	do {
150	if (waitpid(thread, NULL, __WCLONE) >= 0);
151	break;
152	} while (errno == EINTR);
153	if (ret)
154	*ret = NULL;
155	return 0;
156	}
157
158
159	/*
160	* Cancel thread
161	*/
162
163	int pthread_cancel(pthread_t thread)
164	{
165	kill(thread, SIGINT);
166	return 0;
167	}
168
169
170	/*
171	* Test for cancellation
172	*/
173
174	void pthread_testcancel(void)
175	{
176	}
177
178
179	/*
180	* Spinlocks
181	*/
182
183	/* For multiprocessor systems, we want to ensure all memory accesses
184	are completed before we reset a lock. On other systems, we still
185	need to make sure that the compiler has flushed everything to memory. */
186	#define MEMORY_BARRIER() __asm__ __volatile__ ("sync" : : : "memory")
187
188	static void fastlock_init(struct _pthread_fastlock *lock)
189	{
190	lock->status = 0;
191	lock->spinlock = 0;
192	}
193
194	static int fastlock_try_acquire(struct _pthread_fastlock *lock)
195	{
196	int res = EBUSY;
197	if (test_and_set(&lock->spinlock, 1) == 0) {
198	if (lock->status == 0) {
199	lock->status = 1;
200	MEMORY_BARRIER();
201	res = 0;
202	}
203	lock->spinlock = 0;
204	}
205	return res;
206	}
207
208	static void fastlock_acquire(struct _pthread_fastlock *lock)
209	{
210	MEMORY_BARRIER();
211	while (test_and_set(&lock->spinlock, 1))
212	usleep(0);
213	}
214
215	static void fastlock_release(struct _pthread_fastlock *lock)
216	{
217	MEMORY_BARRIER();
218	lock->spinlock = 0;
219	__asm__ __volatile__ ("" : "=m" (lock->spinlock) : "m" (lock->spinlock));
220	}
221
222
223	/*
224	* Initialize mutex
225	*/
226
227	int pthread_mutex_init(pthread_mutex_t mutex, const pthread_mutexattr_t mutex_attr)
228	{
229	fastlock_init(&mutex->__m_lock);
230	mutex->__m_kind = mutex_attr ? mutex_attr->__mutexkind : PTHREAD_MUTEX_TIMED_NP;
231	mutex->__m_count = 0;
232	mutex->__m_owner = NULL;
233	return 0;
234	}
235
236
237	/*
238	* Destroy mutex
239	*/
240
241	int pthread_mutex_destroy(pthread_mutex_t *mutex)
242	{
243	switch (mutex->__m_kind) {
244	case PTHREAD_MUTEX_TIMED_NP:
245	return (mutex->__m_lock.__status != 0) ? EBUSY : 0;
246	default:
247	return EINVAL;
248	}
249	}
250
251
252	/*
253	* Lock mutex
254	*/
255
256	int pthread_mutex_lock(pthread_mutex_t *mutex)
257	{
258	switch (mutex->__m_kind) {
259	case PTHREAD_MUTEX_TIMED_NP:
260	fastlock_acquire(&mutex->__m_lock);
261	return 0;
262	default:
263	return EINVAL;
264	}
265	}
266
267
268	/*
269	* Try to lock mutex
270	*/
271
272	int pthread_mutex_trylock(pthread_mutex_t *mutex)
273	{
274	switch (mutex->__m_kind) {
275	case PTHREAD_MUTEX_TIMED_NP:
276	return fastlock_try_acquire(&mutex->__m_lock);
277	default:
278	return EINVAL;
279	}
280	}
281
282
283	/*
284	* Unlock mutex
285	*/
286
287	int pthread_mutex_unlock(pthread_mutex_t *mutex)
288	{
289	switch (mutex->__m_kind) {
290	case PTHREAD_MUTEX_TIMED_NP:
291	fastlock_release(&mutex->__m_lock);
292	return 0;
293	default:
294	return EINVAL;
295	}
296	}
297
298
299	/*
300	* Create mutex attribute
301	*/
302
303	int pthread_mutexattr_init(pthread_mutexattr_t *attr)
304	{
305	attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
306	return 0;
307	}
308
309
310	/*
311	* Destroy mutex attribute
312	*/
313
314	int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
315	{
316	return 0;
317	}
318
319
320	/*
321	* Init semaphore
322	*/
323
324	int sem_init(sem_t *sem, int pshared, unsigned int value)
325	{
326	if (sem == NULL \|\| value > SEM_VALUE_MAX) {
327	errno = EINVAL;
328	return -1;
329	}
330	if (pshared) {
331	errno = ENOSYS;
332	return -1;
333	}
334	fastlock_init(&sem->sem_lock);
335	sem->sem_value = value;
336	sem->sem_waiting = NULL;
337	return 0;
338	}
339
340
341	/*
342	* Delete remaphore
343	*/
344
345	int sem_destroy(sem_t *sem)
346	{
347	if (sem == NULL) {
348	errno = EINVAL;
349	return -1;
350	}
351	if (sem->sem_waiting) {
352	errno = EBUSY;
353	return -1;
354	}
355	sem->sem_value = 0;
356	sem->sem_waiting = NULL;
357	return 0;
358	}
359
360
361	/*
362	* Wait on semaphore
363	*/
364
365	int sem_wait(sem_t *sem)
366	{
367	if (sem == NULL) {
368	errno = EINVAL;
369	return -1;
370	}
371	fastlock_acquire(&sem->sem_lock);
372	if (sem->sem_value > 0) {
373	sem->sem_value--;
374	fastlock_release(&sem->sem_lock);
375	return 0;
376	}
377	sem->sem_waiting = (struct _pthread_descr_struct *)((long)sem->sem_waiting + 1);
378	while (sem->sem_value == 0) {
379	fastlock_release(&sem->sem_lock);
380	usleep(0);
381	fastlock_acquire(&sem->sem_lock);
382	}
383	sem->sem_value--;
384	fastlock_release(&sem->sem_lock);
385	return 0;
386	}
387
388
389	/*
390	* Post semaphore
391	*/
392
393	int sem_post(sem_t *sem)
394	{
395	if (sem == NULL) {
396	errno = EINVAL;
397	return -1;
398	}
399	fastlock_acquire(&sem->sem_lock);
400	if (sem->sem_waiting)
401	sem->sem_waiting = (struct _pthread_descr_struct *)((long)sem->sem_waiting - 1);
402	else {
403	if (sem->sem_value >= SEM_VALUE_MAX) {
404	errno = ERANGE;
405	fastlock_release(&sem->sem_lock);
406	return -1;
407	}
408	}
409	sem->sem_value++;
410	fastlock_release(&sem->sem_lock);
411	return 0;
412	}
413
414
415	/*
416	* Simple producer/consumer test program
417	*/
418
419	#ifdef TEST
420	#include <stdio.h>
421
422	static sem_t p_sem, c_sem;
423	static int data = 0;
424
425	static void producer_func(void arg)
426	{
427	int i, n = (int)arg;
428	for (i = 0; i < n; i++) {
429	sem_wait(&p_sem);
430	data++;
431	sem_post(&c_sem);
432	}
433	return NULL;
434	}
435
436	static void consumer_func(void arg)
437	{
438	int i, n = (int)arg;
439	for (i = 0; i < n; i++) {
440	sem_wait(&c_sem);
441	printf("data: %d\n", data);
442	sem_post(&p_sem);
443	}
444	sleep(1); // for testing pthread_join()
445	return NULL;
446	}
447
448	int main(void)
449	{
450	pthread_t producer_thread, consumer_thread;
451	static const int N = 5;
452
453	if (sem_init(&c_sem, 0, 0) < 0)
454	return 1;
455	if (sem_init(&p_sem, 0, 1) < 0)
456	return 2;
457	if (pthread_create(&producer_thread, NULL, producer_func, (void *)N) != 0)
458	return 3;
459	if (pthread_create(&consumer_thread, NULL, consumer_func, (void *)N) != 0)
460	return 4;
461	pthread_join(producer_thread, NULL);
462	pthread_join(consumer_thread, NULL);
463	sem_destroy(&p_sem);
464	sem_destroy(&c_sem);
465	if (data != N)
466	return 5;
467	return 0;
468	}
469	#endif