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33574c17 | 1 | /* Allocate a new thread structure. |
d614a753 | 2 | Copyright (C) 2000-2020 Free Software Foundation, Inc. |
33574c17 ST |
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 | |
ad2b41bf ST |
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. | |
33574c17 ST |
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 | |
ad2b41bf | 13 | Lesser General Public License for more details. |
33574c17 | 14 | |
ad2b41bf ST |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see | |
5a82c748 | 17 | <https://www.gnu.org/licenses/>. */ |
33574c17 ST |
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 | /* Thread ID lookup table. */ | |
32 | struct __pthread **__pthread_threads; | |
33 | ||
34 | /* The size of the thread ID lookup table. */ | |
35 | int __pthread_max_threads; | |
36 | ||
37 | /* The total number of thread IDs currently in use, or on the list of | |
38 | available thread IDs. */ | |
39 | int __pthread_num_threads; | |
40 | ||
41 | /* A lock for the table, and the other variables above. */ | |
42 | pthread_rwlock_t __pthread_threads_lock; | |
43 | ||
44 | /* List of thread structures corresponding to free thread IDs. */ | |
45 | struct __pthread *__pthread_free_threads; | |
46 | pthread_mutex_t __pthread_free_threads_lock; | |
47 | ||
48 | static inline error_t | |
49 | initialize_pthread (struct __pthread *new) | |
50 | { | |
51 | error_t err; | |
52 | ||
53 | err = __pthread_init_specific (new); | |
54 | if (err) | |
55 | return err; | |
56 | ||
57 | new->nr_refs = 1; | |
58 | new->cancel_lock = (pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER; | |
59 | new->cancel_hook = NULL; | |
60 | new->cancel_hook_arg = NULL; | |
61 | new->cancel_state = PTHREAD_CANCEL_ENABLE; | |
62 | new->cancel_type = PTHREAD_CANCEL_DEFERRED; | |
63 | new->cancel_pending = 0; | |
64 | ||
65 | new->state_lock = (pthread_mutex_t) PTHREAD_MUTEX_INITIALIZER; | |
66 | new->state_cond = (pthread_cond_t) PTHREAD_COND_INITIALIZER; | |
67 | ||
68 | new->cancelation_handlers = 0; | |
69 | ||
70 | memset (&new->res_state, '\0', sizeof (new->res_state)); | |
71 | ||
72 | new->tcb = NULL; | |
73 | ||
74 | new->next = 0; | |
75 | new->prevp = 0; | |
76 | ||
77 | return 0; | |
78 | } | |
79 | ||
80 | ||
81 | /* Allocate a new thread structure and its pthread thread ID (but not | |
82 | a kernel thread). */ | |
83 | int | |
84 | __pthread_alloc (struct __pthread **pthread) | |
85 | { | |
86 | error_t err; | |
87 | ||
88 | struct __pthread *new; | |
89 | struct __pthread **threads; | |
90 | struct __pthread **old_threads; | |
91 | int max_threads; | |
92 | int new_max_threads; | |
93 | ||
f6fb29d2 | 94 | __pthread_mutex_lock (&__pthread_free_threads_lock); |
33574c17 ST |
95 | for (new = __pthread_free_threads; new; new = new->next) |
96 | { | |
97 | /* There is no need to take NEW->STATE_LOCK: if NEW is on this | |
98 | list, then it is protected by __PTHREAD_FREE_THREADS_LOCK | |
99 | except in __pthread_dealloc where after it is added to the | |
100 | list (with the lock held), it drops the lock and then sets | |
101 | NEW->STATE and immediately stops using NEW. */ | |
102 | if (new->state == PTHREAD_TERMINATED) | |
103 | { | |
104 | __pthread_dequeue (new); | |
105 | break; | |
106 | } | |
107 | } | |
f6fb29d2 | 108 | __pthread_mutex_unlock (&__pthread_free_threads_lock); |
33574c17 ST |
109 | |
110 | if (new) | |
111 | { | |
112 | if (new->tcb) | |
113 | { | |
114 | /* Drop old values */ | |
115 | _dl_deallocate_tls (new->tcb, 1); | |
116 | } | |
117 | ||
118 | err = initialize_pthread (new); | |
119 | if (!err) | |
120 | *pthread = new; | |
121 | return err; | |
122 | } | |
123 | ||
124 | /* Allocate a new thread structure. */ | |
125 | new = malloc (sizeof (struct __pthread)); | |
126 | if (new == NULL) | |
127 | return ENOMEM; | |
128 | ||
129 | err = initialize_pthread (new); | |
130 | if (err) | |
131 | { | |
132 | free (new); | |
133 | return err; | |
134 | } | |
135 | ||
136 | retry: | |
137 | __pthread_rwlock_wrlock (&__pthread_threads_lock); | |
138 | ||
139 | if (__pthread_num_threads < __pthread_max_threads) | |
140 | { | |
141 | /* We have a free slot. Use the slot number plus one as the | |
142 | thread ID for the new thread. */ | |
143 | new->thread = 1 + __pthread_num_threads++; | |
144 | __pthread_threads[new->thread - 1] = NULL; | |
145 | ||
146 | __pthread_rwlock_unlock (&__pthread_threads_lock); | |
147 | ||
148 | *pthread = new; | |
149 | return 0; | |
150 | } | |
151 | #ifdef PTHREAD_THREADS_MAX | |
152 | else if (__pthread_num_threads >= PTHREAD_THREADS_MAX) | |
153 | { | |
154 | /* We have reached the limit on the number of threads per process. */ | |
155 | __pthread_rwlock_unlock (&__pthread_threads_lock); | |
156 | ||
157 | free (new); | |
158 | return EAGAIN; | |
159 | } | |
160 | #endif | |
161 | ||
162 | /* We are going to enlarge the threads table. Save its current | |
163 | size. We're going to release the lock before doing the necessary | |
164 | memory allocation, since that's a potentially blocking operation. */ | |
165 | max_threads = __pthread_max_threads; | |
166 | ||
167 | __pthread_rwlock_unlock (&__pthread_threads_lock); | |
168 | ||
169 | /* Allocate a new lookup table that's twice as large. */ | |
170 | new_max_threads | |
171 | = max_threads > 0 ? max_threads * 2 : _POSIX_THREAD_THREADS_MAX; | |
172 | threads = malloc (new_max_threads * sizeof (struct __pthread *)); | |
173 | if (threads == NULL) | |
174 | { | |
175 | free (new); | |
176 | return ENOMEM; | |
177 | } | |
178 | ||
179 | __pthread_rwlock_wrlock (&__pthread_threads_lock); | |
180 | ||
181 | /* Check if nobody else has already enlarged the table. */ | |
182 | if (max_threads != __pthread_max_threads) | |
183 | { | |
184 | /* Yep, they did. */ | |
185 | __pthread_rwlock_unlock (&__pthread_threads_lock); | |
186 | ||
187 | /* Free the newly allocated table and try again to allocate a slot. */ | |
188 | free (threads); | |
189 | goto retry; | |
190 | } | |
191 | ||
192 | /* Copy over the contents of the old table. */ | |
193 | memcpy (threads, __pthread_threads, | |
194 | __pthread_max_threads * sizeof (struct __pthread *)); | |
195 | ||
196 | /* Save the location of the old table. We want to deallocate its | |
197 | storage after we released the lock. */ | |
198 | old_threads = __pthread_threads; | |
199 | ||
200 | /* Replace the table with the new one. */ | |
201 | __pthread_max_threads = new_max_threads; | |
202 | __pthread_threads = threads; | |
203 | ||
204 | /* And allocate ourselves one of the newly created slots. */ | |
205 | new->thread = 1 + __pthread_num_threads++; | |
206 | __pthread_threads[new->thread - 1] = NULL; | |
207 | ||
208 | __pthread_rwlock_unlock (&__pthread_threads_lock); | |
209 | ||
210 | free (old_threads); | |
211 | ||
212 | *pthread = new; | |
213 | return 0; | |
214 | } |