Unix/Linux/sheepthreads.c

/*
 *  sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
 *                   like nonstandard stacks)
 *
 *  SheepShaver (C) 1997-2002 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


/*
 *  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, 0) >= 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 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;
}


/*
 *  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 (atomic_add((int *)&sem->sem_value, -1) >= 0) {
                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);
        atomic_add((int *)&sem->sem_value, 1);
        if (sem->sem_waiting)
                kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
        release_spinlock(&sem->sem_lock.spinlock);
        return 0;
}
Revision:	1.2
Committed:	2002-04-21T11:42:30Z (22 years, 7 months ago) by gbeauche
Content type:	text/plain
Branch:	MAIN
Changes since 1.1:	+2 -0 lines
Log Message:	Match changes from glibc 2.2 (?) - #define status as __status - #define spinlock as __spinlock
#	Content
1	/*
2	* sheepthreads.c - Minimal pthreads implementation (libpthreads doesn't
3	* like nonstandard stacks)
4	*
5	* SheepShaver (C) 1997-2002 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 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	#define status __status
55	#define spinlock __spinlock
56	#define sem_lock __sem_lock
57	#define sem_value __sem_value
58	#define sem_waiting __sem_waiting
59
60
61	/*
62	* Return pthread ID of self
63	*/
64
65	pthread_t pthread_self(void)
66	{
67	return getpid();
68	}
69
70
71	/*
72	* Test whether two pthread IDs are equal
73	*/
74
75	int pthread_equal(pthread_t t1, pthread_t t2)
76	{
77	return t1 == t2;
78	}
79
80
81	/*
82	* Send signal to thread
83	*/
84
85	int pthread_kill(pthread_t thread, int sig)
86	{
87	if (kill(thread, sig) == -1)
88	return errno;
89	else
90	return 0;
91	}
92
93
94	/*
95	* Create pthread
96	*/
97
98	struct new_thread {
99	void (fn)(void *);
100	void *arg;
101	};
102
103	static int start_thread(void *arg)
104	{
105	struct new_thread nt = (struct new_thread )arg;
106	nt->fn(nt->arg);
107	return 0;
108	}
109
110	int pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg)
111	{
112	struct new_thread *nt;
113	void *stack;
114	int pid;
115
116	nt = (struct new_thread *)malloc(sizeof(struct new_thread));
117	nt->fn = start_routine;
118	nt->arg = arg;
119	stack = malloc(STACK_SIZE);
120
121	pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM \| CLONE_FS \| CLONE_FILES, nt);
122	if (pid == -1) {
123	free(stack);
124	free(nt);
125	return errno;
126	} else {
127	*thread = pid;
128	return 0;
129	}
130	}
131
132
133	/*
134	* Join pthread
135	*/
136
137	int pthread_join(pthread_t thread, void **ret)
138	{
139	do {
140	if (waitpid(thread, NULL, 0) >= 0)
141	break;
142	} while (errno == EINTR);
143	if (ret)
144	*ret = NULL;
145	return 0;
146	}
147
148
149	/*
150	* Cancel thread
151	*/
152
153	int pthread_cancel(pthread_t thread)
154	{
155	kill(thread, SIGINT);
156	return 0;
157	}
158
159
160	/*
161	* Test for cancellation
162	*/
163
164	void pthread_testcancel(void)
165	{
166	}
167
168
169	/*
170	* Spinlocks
171	*/
172
173	static void acquire_spinlock(volatile int *lock)
174	{
175	do {
176	while (*lock) ;
177	} while (test_and_set((int *)lock, 1) != 0);
178	}
179
180	static void release_spinlock(int *lock)
181	{
182	*lock = 0;
183	}
184
185
186	/*
187	* Init semaphore
188	*/
189
190	int sem_init(sem_t *sem, int pshared, unsigned int value)
191	{
192	sem->sem_lock.status = 0;
193	sem->sem_lock.spinlock = 0;
194	sem->sem_value = value;
195	sem->sem_waiting = NULL;
196	return 0;
197	}
198
199
200	/*
201	* Delete remaphore
202	*/
203
204	int sem_destroy(sem_t *sem)
205	{
206	return 0;
207	}
208
209
210	/*
211	* Wait on semaphore
212	*/
213
214	void null_handler(int sig)
215	{
216	}
217
218	int sem_wait(sem_t *sem)
219	{
220	acquire_spinlock(&sem->sem_lock.spinlock);
221	if (atomic_add((int *)&sem->sem_value, -1) >= 0) {
222	sigset_t mask;
223	if (!sem->sem_lock.status) {
224	struct sigaction sa;
225	sem->sem_lock.status = SIGUSR2;
226	sa.sa_handler = null_handler;
227	sa.sa_flags = SA_RESTART;
228	sigemptyset(&sa.sa_mask);
229	sigaction(sem->sem_lock.status, &sa, NULL);
230	}
231	sem->sem_waiting = (struct _pthread_descr_struct *)getpid();
232	sigemptyset(&mask);
233	sigsuspend(&mask);
234	sem->sem_waiting = NULL;
235	}
236	release_spinlock(&sem->sem_lock.spinlock);
237	return 0;
238	}
239
240
241	/*
242	* Post semaphore
243	*/
244
245	int sem_post(sem_t *sem)
246	{
247	acquire_spinlock(&sem->sem_lock.spinlock);
248	atomic_add((int *)&sem->sem_value, 1);
249	if (sem->sem_waiting)
250	kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
251	release_spinlock(&sem->sem_lock.spinlock);
252	return 0;
253	}