Unix/Linux/sheepthreads.c

/*
 *  sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
 *                   like nonstandard stacks)
 *
 *  SheepShaver (C) 1997-2004 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

/* 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
 */

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 (sem->sem_value > 0)
                atomic_add((int *)&sem->sem_value, -1);
        else {
                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);
        if (sem->sem_waiting == NULL)
                atomic_add((int *)&sem->sem_value, 1);
        else
                kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
        release_spinlock(&sem->sem_lock.spinlock);
        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:	1.5
Committed:	2004-01-12T15:55:51Z (20 years, 10 months ago) by cebix
Content type:	text/plain
Branch:	MAIN
Changes since 1.4:	+1 -1 lines
Log Message:	Happy New Year!
#	User	Rev	Content
1	cebix	1.1	/*
2			* sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
3			* like nonstandard stacks)
4			*
5	cebix	1.5	* SheepShaver (C) 1997-2004 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 <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	gbeauche	1.2	#define status __status
55			#define spinlock __spinlock
56	cebix	1.1	#define sem_lock __sem_lock
57			#define sem_value __sem_value
58			#define sem_waiting __sem_waiting
59
60	gbeauche	1.4	/* Wait for "clone" children only (Linux 2.4+ specific) */
61			#ifndef __WCLONE
62			#define __WCLONE 0
63			#endif
64
65	cebix	1.1
66			/*
67			* Return pthread ID of self
68			*/
69
70			pthread_t pthread_self(void)
71			{
72			return getpid();
73			}
74
75
76			/*
77			* Test whether two pthread IDs are equal
78			*/
79
80			int pthread_equal(pthread_t t1, pthread_t t2)
81			{
82			return t1 == t2;
83			}
84
85
86			/*
87			* Send signal to thread
88			*/
89
90			int pthread_kill(pthread_t thread, int sig)
91			{
92			if (kill(thread, sig) == -1)
93			return errno;
94			else
95			return 0;
96			}
97
98
99			/*
100			* Create pthread
101			*/
102
103			struct new_thread {
104			void (fn)(void *);
105			void *arg;
106			};
107
108			static int start_thread(void *arg)
109			{
110			struct new_thread nt = (struct new_thread )arg;
111			nt->fn(nt->arg);
112			return 0;
113			}
114
115			int pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg)
116			{
117			struct new_thread *nt;
118			void *stack;
119			int pid;
120
121			nt = (struct new_thread *)malloc(sizeof(struct new_thread));
122			nt->fn = start_routine;
123			nt->arg = arg;
124			stack = malloc(STACK_SIZE);
125
126			pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM \| CLONE_FS \| CLONE_FILES, nt);
127			if (pid == -1) {
128			free(stack);
129			free(nt);
130			return errno;
131			} else {
132			*thread = pid;
133			return 0;
134			}
135			}
136
137
138			/*
139			* Join pthread
140			*/
141
142			int pthread_join(pthread_t thread, void **ret)
143			{
144			do {
145	gbeauche	1.4	if (waitpid(thread, NULL, __WCLONE) >= 0);
146	cebix	1.1	break;
147			} while (errno == EINTR);
148			if (ret)
149			*ret = NULL;
150			return 0;
151			}
152
153
154			/*
155			* Cancel thread
156			*/
157
158			int pthread_cancel(pthread_t thread)
159			{
160			kill(thread, SIGINT);
161			return 0;
162			}
163
164
165			/*
166			* Test for cancellation
167			*/
168
169			void pthread_testcancel(void)
170			{
171			}
172
173
174			/*
175			* Spinlocks
176			*/
177
178	gbeauche	1.3	static int try_acquire_spinlock(int *lock)
179			{
180			return test_and_set(lock, 1) == 0;
181			}
182
183	cebix	1.1	static void acquire_spinlock(volatile int *lock)
184			{
185			do {
186			while (*lock) ;
187			} while (test_and_set((int *)lock, 1) != 0);
188			}
189
190			static void release_spinlock(int *lock)
191			{
192			*lock = 0;
193	gbeauche	1.3	}
194
195
196			/*
197			* Initialize mutex
198			*/
199
200			int pthread_mutex_init(pthread_mutex_t mutex, const pthread_mutexattr_t mutex_attr)
201			{
202			// pthread_init_lock
203			mutex->__m_lock.__status = 0;
204			mutex->__m_lock.__spinlock = 0;
205
206			mutex->__m_kind = mutex_attr ? mutex_attr->__mutexkind : PTHREAD_MUTEX_TIMED_NP;
207			mutex->__m_count = 0;
208			mutex->__m_owner = NULL;
209			return 0;
210			}
211
212
213			/*
214			* Destroy mutex
215			*/
216
217			int pthread_mutex_destroy(pthread_mutex_t *mutex)
218			{
219			switch (mutex->__m_kind) {
220			case PTHREAD_MUTEX_TIMED_NP:
221			return (mutex->__m_lock.__status != 0) ? EBUSY : 0;
222			default:
223			return EINVAL;
224			}
225			}
226
227
228			/*
229			* Lock mutex
230			*/
231
232			int pthread_mutex_lock(pthread_mutex_t *mutex)
233			{
234			switch (mutex->__m_kind) {
235			case PTHREAD_MUTEX_TIMED_NP:
236			acquire_spinlock(&mutex->__m_lock.__spinlock);
237			return 0;
238			default:
239			return EINVAL;
240			}
241			}
242
243
244			/*
245			* Try to lock mutex
246			*/
247
248			int pthread_mutex_trylock(pthread_mutex_t *mutex)
249			{
250			switch (mutex->__m_kind) {
251			case PTHREAD_MUTEX_TIMED_NP:
252			if (!try_acquire_spinlock(&mutex->__m_lock.__spinlock))
253			return EBUSY;
254			return 0;
255			default:
256			return EINVAL;
257			}
258			}
259
260
261			/*
262			* Unlock mutex
263			*/
264
265			int pthread_mutex_unlock(pthread_mutex_t *mutex)
266			{
267			switch (mutex->__m_kind) {
268			case PTHREAD_MUTEX_TIMED_NP:
269			release_spinlock(&mutex->__m_lock.__spinlock);
270			return 0;
271			default:
272			return EINVAL;
273			}
274			}
275
276
277			/*
278			* Create mutex attribute
279			*/
280
281			int pthread_mutexattr_init(pthread_mutexattr_t *attr)
282			{
283			attr->__mutexkind = PTHREAD_MUTEX_TIMED_NP;
284			return 0;
285			}
286
287
288			/*
289			* Destroy mutex attribute
290			*/
291
292			int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
293			{
294			return 0;
295	cebix	1.1	}
296
297
298			/*
299			* Init semaphore
300			*/
301
302			int sem_init(sem_t *sem, int pshared, unsigned int value)
303			{
304			sem->sem_lock.status = 0;
305			sem->sem_lock.spinlock = 0;
306			sem->sem_value = value;
307			sem->sem_waiting = NULL;
308			return 0;
309			}
310
311
312			/*
313			* Delete remaphore
314			*/
315
316			int sem_destroy(sem_t *sem)
317			{
318			return 0;
319			}
320
321
322			/*
323			* Wait on semaphore
324			*/
325
326			void null_handler(int sig)
327			{
328			}
329
330			int sem_wait(sem_t *sem)
331			{
332			acquire_spinlock(&sem->sem_lock.spinlock);
333	gbeauche	1.4	if (sem->sem_value > 0)
334			atomic_add((int *)&sem->sem_value, -1);
335			else {
336	cebix	1.1	sigset_t mask;
337			if (!sem->sem_lock.status) {
338			struct sigaction sa;
339			sem->sem_lock.status = SIGUSR2;
340			sa.sa_handler = null_handler;
341			sa.sa_flags = SA_RESTART;
342			sigemptyset(&sa.sa_mask);
343			sigaction(sem->sem_lock.status, &sa, NULL);
344			}
345			sem->sem_waiting = (struct _pthread_descr_struct *)getpid();
346			sigemptyset(&mask);
347			sigsuspend(&mask);
348			sem->sem_waiting = NULL;
349			}
350			release_spinlock(&sem->sem_lock.spinlock);
351			return 0;
352			}
353
354
355			/*
356			* Post semaphore
357			*/
358
359			int sem_post(sem_t *sem)
360			{
361			acquire_spinlock(&sem->sem_lock.spinlock);
362	gbeauche	1.4	if (sem->sem_waiting == NULL)
363			atomic_add((int *)&sem->sem_value, 1);
364			else
365	cebix	1.1	kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
366			release_spinlock(&sem->sem_lock.spinlock);
367			return 0;
368			}
369	gbeauche	1.4
370
371			/*
372			* Simple producer/consumer test program
373			*/
374
375			#ifdef TEST
376			#include <stdio.h>
377
378			static sem_t p_sem, c_sem;
379			static int data = 0;
380
381			static void producer_func(void arg)
382			{
383			int i, n = (int)arg;
384			for (i = 0; i < n; i++) {
385			sem_wait(&p_sem);
386			data++;
387			sem_post(&c_sem);
388			}
389			return NULL;
390			}
391
392			static void consumer_func(void arg)
393			{
394			int i, n = (int)arg;
395			for (i = 0; i < n; i++) {
396			sem_wait(&c_sem);
397			printf("data: %d\n", data);
398			sem_post(&p_sem);
399			}
400			sleep(1); // for testing pthread_join()
401			return NULL;
402			}
403
404			int main(void)
405			{
406			pthread_t producer_thread, consumer_thread;
407			static const int N = 5;
408
409			if (sem_init(&c_sem, 0, 0) < 0)
410			return 1;
411			if (sem_init(&p_sem, 0, 1) < 0)
412			return 2;
413			if (pthread_create(&producer_thread, NULL, producer_func, (void *)N) != 0)
414			return 3;
415			if (pthread_create(&consumer_thread, NULL, consumer_func, (void *)N) != 0)
416			return 4;
417			pthread_join(producer_thread, NULL);
418			pthread_join(consumer_thread, NULL);
419			sem_destroy(&p_sem);
420			sem_destroy(&c_sem);
421			if (data != N)
422			return 5;
423			return 0;
424			}
425			#endif