blob: 7ca609f6b2af782c18b94c74cf067b5b329afd1e (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
|
/* Linuxthreads - a simple clone()-based implementation of Posix */
/* threads for Linux. */
/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */
/* */
/* This program is free software; you can redistribute it and/or */
/* modify it under the terms of the GNU Library 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 Library General Public License for more details. */
/* Semaphores a la POSIX 1003.1b */
#include "pthread.h"
#include "semaphore.h"
#include "internals.h"
#include "spinlock.h"
#include "restart.h"
#include "queue.h"
int sem_init(sem_t *sem, int pshared, unsigned int value)
{
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return -1;
}
if (pshared) {
errno = ENOSYS;
return -1;
}
__pthread_init_lock((struct _pthread_fastlock *) &sem->sem_lock);
sem->sem_value = value;
sem->sem_waiting = NULL;
return 0;
}
int sem_wait(sem_t * sem)
{
volatile pthread_descr self;
__pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
if (sem->sem_value > 0) {
sem->sem_value--;
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
return 0;
}
self = thread_self();
enqueue(&sem->sem_waiting, self);
/* Wait for sem_post or cancellation */
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
suspend_with_cancellation(self);
/* This is a cancellation point */
if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) {
/* Remove ourselves from the waiting list if we're still on it */
__pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
remove_from_queue(&sem->sem_waiting, self);
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
pthread_exit(PTHREAD_CANCELED);
}
/* We got the semaphore */
return 0;
}
int sem_trywait(sem_t * sem)
{
int retval;
__pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
if (sem->sem_value == 0) {
errno = EAGAIN;
retval = -1;
} else {
sem->sem_value--;
retval = 0;
}
return retval;
}
int sem_post(sem_t * sem)
{
pthread_descr self = thread_self();
pthread_descr th;
struct pthread_request request;
if (self->p_in_sighandler == NULL) {
__pthread_lock((struct _pthread_fastlock *) &sem->sem_lock);
if (sem->sem_waiting == NULL) {
if (sem->sem_value >= SEM_VALUE_MAX) {
/* Overflow */
errno = ERANGE;
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
return -1;
}
sem->sem_value++;
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
} else {
th = dequeue(&sem->sem_waiting);
__pthread_unlock((struct _pthread_fastlock *) &sem->sem_lock);
restart(th);
}
} else {
/* If we're in signal handler, delegate post operation to
the thread manager. */
if (__pthread_manager_request < 0) {
if (__pthread_initialize_manager() < 0) {
errno = EAGAIN;
return -1;
}
}
request.req_kind = REQ_POST;
request.req_args.post = sem;
__libc_write(__pthread_manager_request,
(char *) &request, sizeof(request));
}
return 0;
}
int sem_getvalue(sem_t * sem, int * sval)
{
*sval = sem->sem_value;
return 0;
}
int sem_destroy(sem_t * sem)
{
if (sem->sem_waiting != NULL) {
errno = EBUSY;
return -1;
}
return 0;
}
|
