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 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:	1.1
Committed:	2002-02-04T16:58:13Z (22 years, 9 months ago) by cebix
Content type:	text/plain
Branch:	MAIN
Branch point for:	cebix
Log Message:	Initial revision
#	User	Rev	Content
1	cebix	1.1	/*
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 sem_lock __sem_lock
55			#define sem_value __sem_value
56			#define sem_waiting __sem_waiting
57
58
59			/*
60			* Return pthread ID of self
61			*/
62
63			pthread_t pthread_self(void)
64			{
65			return getpid();
66			}
67
68
69			/*
70			* Test whether two pthread IDs are equal
71			*/
72
73			int pthread_equal(pthread_t t1, pthread_t t2)
74			{
75			return t1 == t2;
76			}
77
78
79			/*
80			* Send signal to thread
81			*/
82
83			int pthread_kill(pthread_t thread, int sig)
84			{
85			if (kill(thread, sig) == -1)
86			return errno;
87			else
88			return 0;
89			}
90
91
92			/*
93			* Create pthread
94			*/
95
96			struct new_thread {
97			void (fn)(void *);
98			void *arg;
99			};
100
101			static int start_thread(void *arg)
102			{
103			struct new_thread nt = (struct new_thread )arg;
104			nt->fn(nt->arg);
105			return 0;
106			}
107
108			int pthread_create(pthread_t thread, const pthread_attr_t attr, void (start_routine)(void ), void arg)
109			{
110			struct new_thread *nt;
111			void *stack;
112			int pid;
113
114			nt = (struct new_thread *)malloc(sizeof(struct new_thread));
115			nt->fn = start_routine;
116			nt->arg = arg;
117			stack = malloc(STACK_SIZE);
118
119			pid = __clone(start_thread, (char *)stack + STACK_SIZE - 16, CLONE_VM \| CLONE_FS \| CLONE_FILES, nt);
120			if (pid == -1) {
121			free(stack);
122			free(nt);
123			return errno;
124			} else {
125			*thread = pid;
126			return 0;
127			}
128			}
129
130
131			/*
132			* Join pthread
133			*/
134
135			int pthread_join(pthread_t thread, void **ret)
136			{
137			do {
138			if (waitpid(thread, NULL, 0) >= 0)
139			break;
140			} while (errno == EINTR);
141			if (ret)
142			*ret = NULL;
143			return 0;
144			}
145
146
147			/*
148			* Cancel thread
149			*/
150
151			int pthread_cancel(pthread_t thread)
152			{
153			kill(thread, SIGINT);
154			return 0;
155			}
156
157
158			/*
159			* Test for cancellation
160			*/
161
162			void pthread_testcancel(void)
163			{
164			}
165
166
167			/*
168			* Spinlocks
169			*/
170
171			static void acquire_spinlock(volatile int *lock)
172			{
173			do {
174			while (*lock) ;
175			} while (test_and_set((int *)lock, 1) != 0);
176			}
177
178			static void release_spinlock(int *lock)
179			{
180			*lock = 0;
181			}
182
183
184			/*
185			* Init semaphore
186			*/
187
188			int sem_init(sem_t *sem, int pshared, unsigned int value)
189			{
190			sem->sem_lock.status = 0;
191			sem->sem_lock.spinlock = 0;
192			sem->sem_value = value;
193			sem->sem_waiting = NULL;
194			return 0;
195			}
196
197
198			/*
199			* Delete remaphore
200			*/
201
202			int sem_destroy(sem_t *sem)
203			{
204			return 0;
205			}
206
207
208			/*
209			* Wait on semaphore
210			*/
211
212			void null_handler(int sig)
213			{
214			}
215
216			int sem_wait(sem_t *sem)
217			{
218			acquire_spinlock(&sem->sem_lock.spinlock);
219			if (atomic_add((int *)&sem->sem_value, -1) >= 0) {
220			sigset_t mask;
221			if (!sem->sem_lock.status) {
222			struct sigaction sa;
223			sem->sem_lock.status = SIGUSR2;
224			sa.sa_handler = null_handler;
225			sa.sa_flags = SA_RESTART;
226			sigemptyset(&sa.sa_mask);
227			sigaction(sem->sem_lock.status, &sa, NULL);
228			}
229			sem->sem_waiting = (struct _pthread_descr_struct *)getpid();
230			sigemptyset(&mask);
231			sigsuspend(&mask);
232			sem->sem_waiting = NULL;
233			}
234			release_spinlock(&sem->sem_lock.spinlock);
235			return 0;
236			}
237
238
239			/*
240			* Post semaphore
241			*/
242
243			int sem_post(sem_t *sem)
244			{
245			acquire_spinlock(&sem->sem_lock.spinlock);
246			atomic_add((int *)&sem->sem_value, 1);
247			if (sem->sem_waiting)
248			kill((pid_t)sem->sem_waiting, sem->sem_lock.status);
249			release_spinlock(&sem->sem_lock.spinlock);
250			return 0;
251			}