Unix/NetBSD/sheepthreads.c

/*
 *  sheepthreads.c - Minimal pthreads implementation (libpthread doesn't
 *                   like sigaltstack)
 *
 *  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 <sched.h>
#include <pthread.h>
#include <semaphore.h>


/* Thread descriptor */
struct __pthread_st {
        unsigned int tid;
};

/* 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 */
struct _sem_st {
#define SEM_MAGIC 0x09fa4012
        unsigned int sem_magic;
        struct {
                int status;
                int spinlock;
        } sem_lock;
        int sem_value;
        pid_t 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)
{
        static struct __pthread_st self_st;
        static pthread_t self = NULL;
        if (self == NULL) {
                self = &self_st;
                self->tid = getpid();
        }
        return self;
}


/*
 *  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->tid, 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 = malloc(sizeof(**thread));
                if (*thread == NULL)
                        return -1;
                (*thread)->tid = pid;
                return 0;
        }
}


/*
 *  Join pthread
 */

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


/*
 *  Cancel thread
 */

int pthread_cancel(pthread_t thread)
{
        kill(thread->tid, SIGINT);
        thread->tid = (unsigned int)-1;
        free(thread);
        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)
{
        mutex->ptm_magic = _PT_MUTEX_MAGIC;
        mutex->ptm_lock = 0;
        mutex->ptm_owner = NULL;
        return 0;
}


/*
 *  Destroy mutex
 */

int pthread_mutex_destroy(pthread_mutex_t *mutex)
{
        if (mutex->ptm_magic != _PT_MUTEX_MAGIC)
                return EINVAL;
        if (mutex->ptm_lock != 0)
                return EBUSY;

        mutex->ptm_magic = _PT_MUTEX_DEAD;
        return 0;
}


/*
 *  Lock mutex
 */

int pthread_mutex_lock(pthread_mutex_t *mutex)
{
        if (mutex->ptm_magic != _PT_MUTEX_MAGIC)
                return EINVAL;

        acquire_spinlock(&mutex->ptm_lock);
        return 0;
}


/*
 *  Try to lock mutex
 */

int pthread_mutex_trylock(pthread_mutex_t *mutex)
{
        if (mutex->ptm_magic != _PT_MUTEX_MAGIC)
                return EINVAL;

        if (!try_acquire_spinlock(&mutex->ptm_lock))
                return EBUSY;
        return 0;
}


/*
 *  Unlock mutex
 */

int pthread_mutex_unlock(pthread_mutex_t *mutex)
{
        if (mutex->ptm_magic != _PT_MUTEX_MAGIC)
                return EINVAL;

        release_spinlock(&mutex->ptm_lock);
        return 0;
}


/*
 *  Create mutex attribute
 */

int pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
        attr->ptma_magic = _PT_MUTEXATTR_MAGIC;
        return 0;
}


/*
 *  Destroy mutex attribute
 */

int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
{
        if (attr->ptma_magic != _PT_MUTEXATTR_MAGIC)
                return EINVAL;
        return 0;
}


/*
 *  Init semaphore
 */

int sem_init(sem_t *psem, int pshared, unsigned int value)
{
        sem_t sem = malloc(sizeof(*sem));
        if (sem == NULL) {
                errno = ENOSPC;
                return 0;
        }
        *psem = sem;
        sem->sem_magic = SEM_MAGIC;
        sem->sem_lock.status = 0;
        sem->sem_lock.spinlock = 0;
        sem->sem_value = value;
        sem->sem_waiting = 0;
        return 0;
}


/*
 *  Delete remaphore
 */

int sem_destroy(sem_t *sem)
{
        if (sem == NULL || *sem == NULL || (*sem)->sem_magic != SEM_MAGIC) {
                errno = EINVAL;
                return -1;
        }

        free(*sem);
        return 0;
}


/*
 *  Wait on semaphore
 */

void null_handler(int sig)
{
}

int sem_wait(sem_t *psem)
{
        sem_t sem;
        if (psem == NULL || (sem = *psem) == NULL || sem->sem_magic != SEM_MAGIC) {
                errno = EINVAL;
                return -1;
        }
        acquire_spinlock(&sem->sem_lock.spinlock);
        if (sem->sem_value > 0)
                atomic_add(&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 = getpid();
                sigemptyset(&mask);
                sigsuspend(&mask);
                sem->sem_waiting = 0;
        }
        release_spinlock(&sem->sem_lock.spinlock);
        return 0;
}


/*
 *  Post semaphore
 */

int sem_post(sem_t *psem)
{
        sem_t sem;
        if (psem == NULL || (sem = *psem) == NULL || sem->sem_magic != SEM_MAGIC) {
                errno = EINVAL;
                return -1;
        }
        acquire_spinlock(&sem->sem_lock.spinlock);
        if (sem->sem_waiting == 0)
                atomic_add(&sem->sem_value, 1);
        else
                kill(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:	1.1
Committed:	2005-02-20T18:06:40Z (19 years, 8 months ago) by gbeauche
Content type:	text/plain
Branch:	MAIN
CVS Tags:	HEAD
Log Message:	Implement SheepThreads on NetBSD/ppc so that sigaltstack()s are really used
#	Content
1	/*
2	* sheepthreads.c - Minimal pthreads implementation (libpthread doesn't
3	* like sigaltstack)
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 <sched.h>
37	#include <pthread.h>
38	#include <semaphore.h>
39
40
41	/* Thread descriptor */
42	struct __pthread_st {
43	unsigned int tid;
44	};
45
46	/* Thread stack size */
47	#define STACK_SIZE 65536
48
49	/* From asm_linux.S */
50	extern int atomic_add(int *var, int add);
51	extern int atomic_and(int *var, int and);
52	extern int atomic_or(int *var, int or);
53	extern int test_and_set(int *var, int val);
54
55	/* Linux kernel calls */
56	extern int __clone(int (fn)(void ), void , int, void );
57
58	/* struct sem_t */
59	struct _sem_st {
60	#define SEM_MAGIC 0x09fa4012
61	unsigned int sem_magic;
62	struct {
63	int status;
64	int spinlock;
65	} sem_lock;
66	int sem_value;
67	pid_t sem_waiting;
68	};
69
70	/* Wait for "clone" children only (Linux 2.4+ specific) */
71	#ifndef __WCLONE
72	#define __WCLONE 0
73	#endif
74
75
76	/*
77	* Return pthread ID of self
78	*/
79
80	pthread_t pthread_self(void)
81	{
82	static struct __pthread_st self_st;
83	static pthread_t self = NULL;
84	if (self == NULL) {
85	self = &self_st;
86	self->tid = getpid();
87	}
88	return self;
89	}
90
91
92	/*
93	* Test whether two pthread IDs are equal
94	*/
95
96	int pthread_equal(pthread_t t1, pthread_t t2)
97	{
98	return t1 == t2;
99	}
100
101
102	/*
103	* Send signal to thread
104	*/
105
106	int pthread_kill(pthread_t thread, int sig)
107	{
108	if (kill(thread->tid, sig) == -1)
109	return errno;
110	else
111	return 0;
112	}
113
114
115	/*
116	* Create pthread
117	*/
118
119	struct new_thread {
120	void (fn)(void *);
121	void *arg;
122	};
123
124	static int start_thread(void *arg)
125	{
126	struct new_thread nt = (struct new_thread )arg;
127	nt->fn(nt->arg);
128	return 0;
129	}
130
131	int pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg)
132	{
133	struct new_thread *nt;
134	void *stack;
135	int pid;
136
137	nt = (struct new_thread *)malloc(sizeof(struct new_thread));
138	nt->fn = start_routine;
139	nt->arg = arg;
140	stack = malloc(STACK_SIZE);
141
142	pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM \| CLONE_FS \| CLONE_FILES, nt);
143	if (pid == -1) {
144	free(stack);
145	free(nt);
146	return errno;
147	} else {
148	thread = malloc(sizeof(*thread));
149	if (*thread == NULL)
150	return -1;
151	(*thread)->tid = pid;
152	return 0;
153	}
154	}
155
156
157	/*
158	* Join pthread
159	*/
160
161	int pthread_join(pthread_t thread, void **ret)
162	{
163	do {
164	if (waitpid(thread->tid, NULL, __WCLONE) >= 0);
165	break;
166	} while (errno == EINTR);
167	if (ret)
168	*ret = NULL;
169	return 0;
170	}
171
172
173	/*
174	* Cancel thread
175	*/
176
177	int pthread_cancel(pthread_t thread)
178	{
179	kill(thread->tid, SIGINT);
180	thread->tid = (unsigned int)-1;
181	free(thread);
182	return 0;
183	}
184
185
186	/*
187	* Test for cancellation
188	*/
189
190	void pthread_testcancel(void)
191	{
192	}
193
194
195	/*
196	* Spinlocks
197	*/
198
199	static int try_acquire_spinlock(int *lock)
200	{
201	return test_and_set(lock, 1) == 0;
202	}
203
204	static void acquire_spinlock(volatile int *lock)
205	{
206	do {
207	while (*lock) ;
208	} while (test_and_set((int *)lock, 1) != 0);
209	}
210
211	static void release_spinlock(int *lock)
212	{
213	*lock = 0;
214	}
215
216
217	/*
218	* Initialize mutex
219	*/
220
221	int pthread_mutex_init(pthread_mutex_t mutex, const pthread_mutexattr_t mutex_attr)
222	{
223	mutex->ptm_magic = _PT_MUTEX_MAGIC;
224	mutex->ptm_lock = 0;
225	mutex->ptm_owner = NULL;
226	return 0;
227	}
228
229
230	/*
231	* Destroy mutex
232	*/
233
234	int pthread_mutex_destroy(pthread_mutex_t *mutex)
235	{
236	if (mutex->ptm_magic != _PT_MUTEX_MAGIC)
237	return EINVAL;
238	if (mutex->ptm_lock != 0)
239	return EBUSY;
240
241	mutex->ptm_magic = _PT_MUTEX_DEAD;
242	return 0;
243	}
244
245
246	/*
247	* Lock mutex
248	*/
249
250	int pthread_mutex_lock(pthread_mutex_t *mutex)
251	{
252	if (mutex->ptm_magic != _PT_MUTEX_MAGIC)
253	return EINVAL;
254
255	acquire_spinlock(&mutex->ptm_lock);
256	return 0;
257	}
258
259
260	/*
261	* Try to lock mutex
262	*/
263
264	int pthread_mutex_trylock(pthread_mutex_t *mutex)
265	{
266	if (mutex->ptm_magic != _PT_MUTEX_MAGIC)
267	return EINVAL;
268
269	if (!try_acquire_spinlock(&mutex->ptm_lock))
270	return EBUSY;
271	return 0;
272	}
273
274
275	/*
276	* Unlock mutex
277	*/
278
279	int pthread_mutex_unlock(pthread_mutex_t *mutex)
280	{
281	if (mutex->ptm_magic != _PT_MUTEX_MAGIC)
282	return EINVAL;
283
284	release_spinlock(&mutex->ptm_lock);
285	return 0;
286	}
287
288
289	/*
290	* Create mutex attribute
291	*/
292
293	int pthread_mutexattr_init(pthread_mutexattr_t *attr)
294	{
295	attr->ptma_magic = _PT_MUTEXATTR_MAGIC;
296	return 0;
297	}
298
299
300	/*
301	* Destroy mutex attribute
302	*/
303
304	int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
305	{
306	if (attr->ptma_magic != _PT_MUTEXATTR_MAGIC)
307	return EINVAL;
308	return 0;
309	}
310
311
312	/*
313	* Init semaphore
314	*/
315
316	int sem_init(sem_t *psem, int pshared, unsigned int value)
317	{
318	sem_t sem = malloc(sizeof(*sem));
319	if (sem == NULL) {
320	errno = ENOSPC;
321	return 0;
322	}
323	*psem = sem;
324	sem->sem_magic = SEM_MAGIC;
325	sem->sem_lock.status = 0;
326	sem->sem_lock.spinlock = 0;
327	sem->sem_value = value;
328	sem->sem_waiting = 0;
329	return 0;
330	}
331
332
333	/*
334	* Delete remaphore
335	*/
336
337	int sem_destroy(sem_t *sem)
338	{
339	if (sem == NULL \|\| sem == NULL \|\| (sem)->sem_magic != SEM_MAGIC) {
340	errno = EINVAL;
341	return -1;
342	}
343
344	free(*sem);
345	return 0;
346	}
347
348
349	/*
350	* Wait on semaphore
351	*/
352
353	void null_handler(int sig)
354	{
355	}
356
357	int sem_wait(sem_t *psem)
358	{
359	sem_t sem;
360	if (psem == NULL \|\| (sem = *psem) == NULL \|\| sem->sem_magic != SEM_MAGIC) {
361	errno = EINVAL;
362	return -1;
363	}
364	acquire_spinlock(&sem->sem_lock.spinlock);
365	if (sem->sem_value > 0)
366	atomic_add(&sem->sem_value, -1);
367	else {
368	sigset_t mask;
369	if (!sem->sem_lock.status) {
370	struct sigaction sa;
371	sem->sem_lock.status = SIGUSR2;
372	sa.sa_handler = null_handler;
373	sa.sa_flags = SA_RESTART;
374	sigemptyset(&sa.sa_mask);
375	sigaction(sem->sem_lock.status, &sa, NULL);
376	}
377	sem->sem_waiting = getpid();
378	sigemptyset(&mask);
379	sigsuspend(&mask);
380	sem->sem_waiting = 0;
381	}
382	release_spinlock(&sem->sem_lock.spinlock);
383	return 0;
384	}
385
386
387	/*
388	* Post semaphore
389	*/
390
391	int sem_post(sem_t *psem)
392	{
393	sem_t sem;
394	if (psem == NULL \|\| (sem = *psem) == NULL \|\| sem->sem_magic != SEM_MAGIC) {
395	errno = EINVAL;
396	return -1;
397	}
398	acquire_spinlock(&sem->sem_lock.spinlock);
399	if (sem->sem_waiting == 0)
400	atomic_add(&sem->sem_value, 1);
401	else
402	kill(sem->sem_waiting, sem->sem_lock.status);
403	release_spinlock(&sem->sem_lock.spinlock);
404	return 0;
405	}
406
407
408	/*
409	* Simple producer/consumer test program
410	*/
411
412	#ifdef TEST
413	#include <stdio.h>
414
415	static sem_t p_sem, c_sem;
416	static int data = 0;
417
418	static void producer_func(void arg)
419	{
420	int i, n = (int)arg;
421	for (i = 0; i < n; i++) {
422	sem_wait(&p_sem);
423	data++;
424	sem_post(&c_sem);
425	}
426	return NULL;
427	}
428
429	static void consumer_func(void arg)
430	{
431	int i, n = (int)arg;
432	for (i = 0; i < n; i++) {
433	sem_wait(&c_sem);
434	printf("data: %d\n", data);
435	sem_post(&p_sem);
436	}
437	sleep(1); // for testing pthread_join()
438	return NULL;
439	}
440
441	int main(void)
442	{
443	pthread_t producer_thread, consumer_thread;
444	static const int N = 5;
445
446	if (sem_init(&c_sem, 0, 0) < 0)
447	return 1;
448	if (sem_init(&p_sem, 0, 1) < 0)
449	return 2;
450	if (pthread_create(&producer_thread, NULL, producer_func, (void *)N) != 0)
451	return 3;
452	if (pthread_create(&consumer_thread, NULL, consumer_func, (void *)N) != 0)
453	return 4;
454	pthread_join(producer_thread, NULL);
455	pthread_join(consumer_thread, NULL);
456	sem_destroy(&p_sem);
457	sem_destroy(&c_sem);
458	if (data != N)
459	return 5;
460	return 0;
461	}
462	#endif