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
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
|
/* Linuxthreads - a simple clone()-based implementation of Posix */
/* threads for Linux. */
/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */
/* and Pavel Krauz (krauz@fsid.cvut.cz). */
/* */
/* 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. */
/* Condition variables */
#include <errno.h>
#include <sched.h>
#include <stddef.h>
#include <sys/time.h>
#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
#include "queue.h"
#include "restart.h"
int pthread_cond_init(pthread_cond_t *cond,
const pthread_condattr_t *cond_attr)
{
__pthread_init_lock(&cond->__c_lock);
cond->__c_waiting = NULL;
return 0;
}
int pthread_cond_destroy(pthread_cond_t *cond)
{
if (cond->__c_waiting != NULL) return EBUSY;
return 0;
}
int pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
{
volatile pthread_descr self = thread_self();
__pthread_lock(&cond->__c_lock, self);
enqueue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
pthread_mutex_unlock(mutex);
suspend_with_cancellation(self);
pthread_mutex_lock(mutex);
/* This is a cancellation point */
if (THREAD_GETMEM(self, p_canceled)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
/* Remove ourselves from the waiting queue if we're still on it */
__pthread_lock(&cond->__c_lock, self);
remove_from_queue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
pthread_exit(PTHREAD_CANCELED);
}
return 0;
}
static inline int
pthread_cond_timedwait_relative(pthread_cond_t *cond,
pthread_mutex_t *mutex,
const struct timespec * reltime)
{
volatile pthread_descr self = thread_self();
sigset_t unblock, initial_mask;
int retsleep;
sigjmp_buf jmpbuf;
/* Wait on the condition */
__pthread_lock(&cond->__c_lock, self);
enqueue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
pthread_mutex_unlock(mutex);
continue_waiting:
/* Set up a longjmp handler for the restart and cancel signals */
if (sigsetjmp(jmpbuf, 1) == 0) {
THREAD_SETMEM(self, p_signal_jmp, &jmpbuf);
THREAD_SETMEM(self, p_cancel_jmp, &jmpbuf);
THREAD_SETMEM(self, p_signal, 0);
/* Check for cancellation */
if (THREAD_GETMEM(self, p_canceled)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
retsleep = -1;
} else {
/* Unblock the restart signal */
sigemptyset(&unblock);
sigaddset(&unblock, __pthread_sig_restart);
sigprocmask(SIG_UNBLOCK, &unblock, &initial_mask);
/* Sleep for the required duration */
retsleep = __libc_nanosleep(reltime, NULL);
/* Block the restart signal again */
sigprocmask(SIG_SETMASK, &initial_mask, NULL);
}
} else {
retsleep = -1;
}
THREAD_SETMEM(self, p_signal_jmp, NULL);
THREAD_SETMEM(self, p_cancel_jmp, NULL);
/* Here, either the condition was signaled (self->p_signal != 0)
or we got canceled (self->p_canceled != 0)
or the timeout occurred (retsleep == 0)
or another interrupt occurred (retsleep == -1) */
/* This is a cancellation point */
if (THREAD_GETMEM(self, p_canceled)
&& THREAD_GETMEM(self, p_cancelstate) == PTHREAD_CANCEL_ENABLE) {
__pthread_lock(&cond->__c_lock, self);
remove_from_queue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
pthread_mutex_lock(mutex);
pthread_exit(PTHREAD_CANCELED);
}
/* If not signaled: also remove ourselves and return an error code, but
only if the timeout has elapsed. If not, just continue waiting. */
if (THREAD_GETMEM(self, p_signal) == 0) {
if (retsleep != 0)
goto continue_waiting;
__pthread_lock(&cond->__c_lock, self);
remove_from_queue(&cond->__c_waiting, self);
__pthread_unlock(&cond->__c_lock);
pthread_mutex_lock(mutex);
return ETIMEDOUT;
}
/* Otherwise, return normally */
pthread_mutex_lock(mutex);
return 0;
}
int pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
const struct timespec * abstime)
{
struct timeval now;
struct timespec reltime;
/* Compute a time offset relative to now */
__gettimeofday(&now, NULL);
reltime.tv_sec = abstime->tv_sec - now.tv_sec;
reltime.tv_nsec = abstime->tv_nsec - now.tv_usec * 1000;
if (reltime.tv_nsec < 0) {
reltime.tv_nsec += 1000000000;
reltime.tv_sec -= 1;
}
if (reltime.tv_sec < 0) return ETIMEDOUT;
return pthread_cond_timedwait_relative(cond, mutex, &reltime);
}
int pthread_cond_signal(pthread_cond_t *cond)
{
pthread_descr th;
__pthread_lock(&cond->__c_lock, NULL);
th = dequeue(&cond->__c_waiting);
__pthread_unlock(&cond->__c_lock);
if (th != NULL) restart(th);
return 0;
}
int pthread_cond_broadcast(pthread_cond_t *cond)
{
pthread_descr tosignal, th;
__pthread_lock(&cond->__c_lock, NULL);
/* Copy the current state of the waiting queue and empty it */
tosignal = cond->__c_waiting;
cond->__c_waiting = NULL;
__pthread_unlock(&cond->__c_lock);
/* Now signal each process in the queue */
while ((th = dequeue(&tosignal)) != NULL) restart(th);
return 0;
}
int pthread_condattr_init(pthread_condattr_t *attr)
{
return 0;
}
int pthread_condattr_destroy(pthread_condattr_t *attr)
{
return 0;
}
|
