1/* Allocate a new thread structure.
2 Copyright (C) 2000-2024 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <assert.h>
20#include <errno.h>
21#include <pthread.h>
22#include <stdlib.h>
23#include <string.h>
24
25#include <pt-internal.h>
26
27/* This braindamage is necessary because the standard says that some
28 of the threads functions "shall fail" if "No thread could be found
29 corresponding to that specified by the given thread ID." */
30
31/* The size of the thread ID lookup table. */
32int __pthread_max_threads;
33
34/* List of thread structures corresponding to free thread IDs. */
35struct __pthread *__pthread_free_threads;
36pthread_mutex_t __pthread_free_threads_lock;
37
38static inline error_t
39initialize_pthread (struct __pthread *new)
40{
41 error_t err;
42
43 err = __pthread_init_specific (thread: new);
44 if (err)
45 return err;
46
47 new->nr_refs = 1;
48 new->cancel_lock = (pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER;
49 new->cancel_hook = NULL;
50 new->cancel_hook_arg = NULL;
51 new->cancel_state = PTHREAD_CANCEL_ENABLE;
52 new->cancel_type = PTHREAD_CANCEL_DEFERRED;
53 new->cancel_pending = 0;
54
55 new->state_lock = (pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER;
56 new->state_cond = (pthread_cond_t) PTHREAD_COND_INITIALIZER;
57 new->terminated = FALSE;
58
59 memset (&new->res_state, '\0', sizeof (new->res_state));
60
61 new->tcb = NULL;
62
63 new->next = 0;
64 new->prevp = 0;
65
66 return 0;
67}
68
69
70/* Allocate a new thread structure and its pthread thread ID (but not
71 a kernel thread). */
72int
73__pthread_alloc (struct __pthread **pthread)
74{
75 error_t err;
76
77 struct __pthread *new;
78 struct __pthread **threads;
79 struct __pthread **old_threads;
80 int max_threads;
81 int new_max_threads;
82
83 __pthread_mutex_lock (&__pthread_free_threads_lock);
84 for (new = __pthread_free_threads; new; new = new->next)
85 {
86 /* There is no need to take NEW->STATE_LOCK: if NEW is on this
87 list, then it is protected by __PTHREAD_FREE_THREADS_LOCK
88 except in __pthread_dealloc_finish where after it is added to the
89 list (with the lock held), it drops the lock and then sets
90 NEW->STATE and immediately stops using NEW. */
91 if (new->terminated)
92 {
93 __pthread_dequeue (thread: new);
94 break;
95 }
96 }
97 __pthread_mutex_unlock (&__pthread_free_threads_lock);
98
99 if (new)
100 {
101 if (new->tcb)
102 {
103 /* Drop old values */
104 _dl_deallocate_tls (new->tcb, 1);
105 }
106
107 err = initialize_pthread (new);
108 if (!err)
109 *pthread = new;
110 return err;
111 }
112
113 /* Allocate a new thread structure. */
114 new = malloc (size: sizeof (struct __pthread));
115 if (new == NULL)
116 return ENOMEM;
117
118 err = initialize_pthread (new);
119 if (err)
120 {
121 free (ptr: new);
122 return err;
123 }
124
125retry:
126 __libc_rwlock_wrlock (GL (dl_pthread_threads_lock));
127
128 if (GL (dl_pthread_num_threads) < __pthread_max_threads)
129 {
130 /* We have a free slot. Use the slot number plus one as the
131 thread ID for the new thread. */
132 new->thread = 1 + GL (dl_pthread_num_threads)++;
133 GL (dl_pthread_threads)[new->thread - 1] = NULL;
134
135 __libc_rwlock_unlock (GL (dl_pthread_threads_lock));
136
137 *pthread = new;
138 return 0;
139 }
140#ifdef PTHREAD_THREADS_MAX
141 else if (GL (dl_pthread_num_threads) >= PTHREAD_THREADS_MAX)
142 {
143 /* We have reached the limit on the number of threads per process. */
144 __libc_rwlock_unlock (GL (dl_pthread_threads_lock));
145
146 free (new);
147 return EAGAIN;
148 }
149#endif
150
151 /* We are going to enlarge the threads table. Save its current
152 size. We're going to release the lock before doing the necessary
153 memory allocation, since that's a potentially blocking operation. */
154 max_threads = __pthread_max_threads;
155
156 __libc_rwlock_unlock (GL (dl_pthread_threads_lock));
157
158 /* Allocate a new lookup table that's twice as large. */
159 new_max_threads
160 = max_threads > 0 ? max_threads * 2 : _POSIX_THREAD_THREADS_MAX;
161 threads = malloc (size: new_max_threads * sizeof (struct __pthread *));
162 if (threads == NULL)
163 {
164 free (ptr: new);
165 return ENOMEM;
166 }
167
168 __libc_rwlock_wrlock (GL (dl_pthread_threads_lock));
169
170 /* Check if nobody else has already enlarged the table. */
171 if (max_threads != __pthread_max_threads)
172 {
173 /* Yep, they did. */
174 __libc_rwlock_unlock (GL (dl_pthread_threads_lock));
175
176 /* Free the newly allocated table and try again to allocate a slot. */
177 free (ptr: threads);
178 goto retry;
179 }
180
181 /* Copy over the contents of the old table. */
182 memcpy (dest: threads, src: GL (dl_pthread_threads),
183 n: __pthread_max_threads * sizeof (struct __pthread *));
184
185 /* Save the location of the old table. We want to deallocate its
186 storage after we released the lock. */
187 old_threads = GL (dl_pthread_threads);
188
189 /* Replace the table with the new one. */
190 __pthread_max_threads = new_max_threads;
191 GL (dl_pthread_threads) = threads;
192
193 /* And allocate ourselves one of the newly created slots. */
194 new->thread = 1 + GL (dl_pthread_num_threads)++;
195 GL (dl_pthread_threads)[new->thread - 1] = NULL;
196
197 __libc_rwlock_unlock (GL (dl_pthread_threads_lock));
198
199 free (ptr: old_threads);
200
201 *pthread = new;
202 return 0;
203}
204
205void
206attribute_hidden
207__pthread_init_static_tls (struct link_map *map)
208{
209 int i;
210
211 __libc_rwlock_wrlock (GL (dl_pthread_threads_lock));
212 for (i = 0; i < GL (dl_pthread_num_threads); ++i)
213 {
214 struct __pthread *t = GL (dl_pthread_threads)[i];
215
216 if (t == NULL)
217 continue;
218
219# if TLS_TCB_AT_TP
220 void *dest = (char *) t->tcb - map->l_tls_offset;
221# elif TLS_DTV_AT_TP
222 void *dest = (char *) t->tcb + map->l_tls_offset + TLS_PRE_TCB_SIZE;
223# else
224# error "Either TLS_TCB_AT_TP or TLS_DTV_AT_TP must be defined"
225# endif
226
227 /* Initialize the memory. */
228 memset (__mempcpy (dest, map->l_tls_initimage, map->l_tls_initimage_size),
229 c: '\0', n: map->l_tls_blocksize - map->l_tls_initimage_size);
230 }
231 __libc_rwlock_unlock (GL (dl_pthread_threads_lock));
232}
233

source code of glibc/htl/pt-alloc.c