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.
#	User	Rev	Content
1	cebix	1.1	/*
2			* sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
3			* like nonstandard stacks)
4			*
5	gbeauche	1.6	* SheepShaver (C) 1997-2005 Christian Bauer and Marc Hellwig
6	cebix	1.1	*
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	gbeauche	1.9	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	gbeauche	1.2	#define status __status
60			#define spinlock __spinlock
61	cebix	1.1	#define sem_lock __sem_lock
62			#define sem_value __sem_value
63			#define sem_waiting __sem_waiting
64
65	gbeauche	1.4	/* Wait for "clone" children only (Linux 2.4+ specific) */
66			#ifndef __WCLONE
67			#define __WCLONE 0
68			#endif
69
70	cebix	1.1
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	gbeauche	1.4	if (waitpid(thread, NULL, __WCLONE) >= 0);
151	cebix	1.1	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	gbeauche	1.7	/* 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	gbeauche	1.3	{
190	gbeauche	1.7	lock->status = 0;
191			lock->spinlock = 0;
192	gbeauche	1.3	}
193
194	gbeauche	1.7	static int fastlock_try_acquire(struct _pthread_fastlock *lock)
195	cebix	1.1	{
196	gbeauche	1.7	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	cebix	1.1	}
214
215	gbeauche	1.7	static void fastlock_release(struct _pthread_fastlock *lock)
216	cebix	1.1	{
217	gbeauche	1.7	MEMORY_BARRIER();
218			lock->spinlock = 0;
219			__asm__ __volatile__ ("" : "=m" (lock->spinlock) : "m" (lock->spinlock));
220	gbeauche	1.3	}
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	gbeauche	1.7	fastlock_init(&mutex->__m_lock);
230	gbeauche	1.3	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	gbeauche	1.7	fastlock_acquire(&mutex->__m_lock);
261	gbeauche	1.3	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	gbeauche	1.7	return fastlock_try_acquire(&mutex->__m_lock);
277	gbeauche	1.3	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	gbeauche	1.7	fastlock_release(&mutex->__m_lock);
292	gbeauche	1.3	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	cebix	1.1	}
318
319
320			/*
321			* Init semaphore
322			*/
323
324			int sem_init(sem_t *sem, int pshared, unsigned int value)
325			{
326	gbeauche	1.7	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	cebix	1.1	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	gbeauche	1.7	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	cebix	1.1	return 0;
358			}
359
360
361			/*
362			* Wait on semaphore
363			*/
364
365	gbeauche	1.7	int sem_wait(sem_t *sem)
366	cebix	1.1	{
367	gbeauche	1.7	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	cebix	1.1	}
383	gbeauche	1.7	sem->sem_value--;
384			fastlock_release(&sem->sem_lock);
385	cebix	1.1	return 0;
386			}
387
388
389			/*
390			* Post semaphore
391			*/
392
393			int sem_post(sem_t *sem)
394			{
395	gbeauche	1.7	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	cebix	1.1	return 0;
412			}
413	gbeauche	1.4
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