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, 9 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
#	User	Rev	Content
1	gbeauche	1.1	/*
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