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
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
|
/* Allocate a new thread structure.
Copyright (C) 2000-2019 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <assert.h>
#include <errno.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
#include <pt-internal.h>
/* This braindamage is necessary because the standard says that some
of the threads functions "shall fail" if "No thread could be found
corresponding to that specified by the given thread ID." */
/* Thread ID lookup table. */
struct __pthread **__pthread_threads;
/* The size of the thread ID lookup table. */
int __pthread_max_threads;
/* The total number of thread IDs currently in use, or on the list of
available thread IDs. */
int __pthread_num_threads;
/* A lock for the table, and the other variables above. */
pthread_rwlock_t __pthread_threads_lock;
/* List of thread structures corresponding to free thread IDs. */
struct __pthread *__pthread_free_threads;
pthread_mutex_t __pthread_free_threads_lock;
static inline error_t
initialize_pthread (struct __pthread *new)
{
error_t err;
err = __pthread_init_specific (new);
if (err)
return err;
new->nr_refs = 1;
new->cancel_lock = (pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER;
new->cancel_hook = NULL;
new->cancel_hook_arg = NULL;
new->cancel_state = PTHREAD_CANCEL_ENABLE;
new->cancel_type = PTHREAD_CANCEL_DEFERRED;
new->cancel_pending = 0;
new->state_lock = (pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER;
new->state_cond = (pthread_cond_t) PTHREAD_COND_INITIALIZER;
new->cancelation_handlers = 0;
memset (&new->res_state, '\0', sizeof (new->res_state));
new->tcb = NULL;
new->next = 0;
new->prevp = 0;
return 0;
}
/* Allocate a new thread structure and its pthread thread ID (but not
a kernel thread). */
int
__pthread_alloc (struct __pthread **pthread)
{
error_t err;
struct __pthread *new;
struct __pthread **threads;
struct __pthread **old_threads;
int max_threads;
int new_max_threads;
__pthread_mutex_lock (&__pthread_free_threads_lock);
for (new = __pthread_free_threads; new; new = new->next)
{
/* There is no need to take NEW->STATE_LOCK: if NEW is on this
list, then it is protected by __PTHREAD_FREE_THREADS_LOCK
except in __pthread_dealloc where after it is added to the
list (with the lock held), it drops the lock and then sets
NEW->STATE and immediately stops using NEW. */
if (new->state == PTHREAD_TERMINATED)
{
__pthread_dequeue (new);
break;
}
}
__pthread_mutex_unlock (&__pthread_free_threads_lock);
if (new)
{
if (new->tcb)
{
/* Drop old values */
_dl_deallocate_tls (new->tcb, 1);
}
err = initialize_pthread (new);
if (!err)
*pthread = new;
return err;
}
/* Allocate a new thread structure. */
new = malloc (sizeof (struct __pthread));
if (new == NULL)
return ENOMEM;
err = initialize_pthread (new);
if (err)
{
free (new);
return err;
}
retry:
__pthread_rwlock_wrlock (&__pthread_threads_lock);
if (__pthread_num_threads < __pthread_max_threads)
{
/* We have a free slot. Use the slot number plus one as the
thread ID for the new thread. */
new->thread = 1 + __pthread_num_threads++;
__pthread_threads[new->thread - 1] = NULL;
__pthread_rwlock_unlock (&__pthread_threads_lock);
*pthread = new;
return 0;
}
#ifdef PTHREAD_THREADS_MAX
else if (__pthread_num_threads >= PTHREAD_THREADS_MAX)
{
/* We have reached the limit on the number of threads per process. */
__pthread_rwlock_unlock (&__pthread_threads_lock);
free (new);
return EAGAIN;
}
#endif
/* We are going to enlarge the threads table. Save its current
size. We're going to release the lock before doing the necessary
memory allocation, since that's a potentially blocking operation. */
max_threads = __pthread_max_threads;
__pthread_rwlock_unlock (&__pthread_threads_lock);
/* Allocate a new lookup table that's twice as large. */
new_max_threads
= max_threads > 0 ? max_threads * 2 : _POSIX_THREAD_THREADS_MAX;
threads = malloc (new_max_threads * sizeof (struct __pthread *));
if (threads == NULL)
{
free (new);
return ENOMEM;
}
__pthread_rwlock_wrlock (&__pthread_threads_lock);
/* Check if nobody else has already enlarged the table. */
if (max_threads != __pthread_max_threads)
{
/* Yep, they did. */
__pthread_rwlock_unlock (&__pthread_threads_lock);
/* Free the newly allocated table and try again to allocate a slot. */
free (threads);
goto retry;
}
/* Copy over the contents of the old table. */
memcpy (threads, __pthread_threads,
__pthread_max_threads * sizeof (struct __pthread *));
/* Save the location of the old table. We want to deallocate its
storage after we released the lock. */
old_threads = __pthread_threads;
/* Replace the table with the new one. */
__pthread_max_threads = new_max_threads;
__pthread_threads = threads;
/* And allocate ourselves one of the newly created slots. */
new->thread = 1 + __pthread_num_threads++;
__pthread_threads[new->thread - 1] = NULL;
__pthread_rwlock_unlock (&__pthread_threads_lock);
free (old_threads);
*pthread = new;
return 0;
}
|
