1/* Thread creation.
2 Copyright (C) 2000-2022 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 <signal.h>
23#include <resolv.h>
24
25#include <atomic.h>
26#include <hurd/resource.h>
27#include <sys/single_threaded.h>
28
29#include <pt-internal.h>
30#include <pthreadP.h>
31
32#if IS_IN (libpthread)
33# include <ctype.h>
34#endif
35#ifdef HAVE_USELOCALE
36# include <locale.h>
37#endif
38
39/* The total number of pthreads currently active. This is defined
40 here since it would be really stupid to have a threads-using
41 program that doesn't call `pthread_create'. */
42unsigned int __pthread_total;
43
44
45/* The entry-point for new threads. */
46static void
47entry_point (struct __pthread *self, void *(*start_routine) (void *), void *arg)
48{
49 int err;
50
51 ___pthread_self = self;
52 __resp = &self->res_state;
53
54#if IS_IN (libpthread)
55 /* Initialize pointers to locale data. */
56 __ctype_init ();
57#endif
58#ifdef HAVE_USELOCALE
59 /* A fresh thread needs to be bound to the global locale. */
60 uselocale (LC_GLOBAL_LOCALE);
61#endif
62
63 __pthread_startup ();
64
65 /* We can now unleash signals. */
66 err = __pthread_sigstate (thread: self, SIG_SETMASK, set: &self->init_sigset, oset: 0, clear_pending: 0);
67 assert_perror (err);
68
69 if (self->c11)
70 {
71 /* The function pointer of the c11 thread start is cast to an incorrect
72 type on __pthread_create call, however it is casted back to correct
73 one so the call behavior is well-defined (it is assumed that pointers
74 to void are able to represent all values of int). */
75 int (*start)(void*) = (int (*) (void*)) start_routine;
76 __pthread_exit (value: (void*) (uintptr_t) start (arg));
77 }
78 else
79 __pthread_exit (value: start_routine (arg));
80}
81
82/* Create a thread with attributes given by ATTR, executing
83 START_ROUTINE with argument ARG. */
84int
85__pthread_create (pthread_t * thread, const pthread_attr_t * attr,
86 void *(*start_routine) (void *), void *arg)
87{
88 int err;
89 struct __pthread *pthread;
90
91 err = __pthread_create_internal (pthread: &pthread, attr, start_routine, arg);
92 if (!err)
93 *thread = pthread->thread;
94 else if (err == ENOMEM)
95 err = EAGAIN;
96
97 return err;
98}
99weak_alias (__pthread_create, pthread_create)
100hidden_def (__pthread_create)
101
102/* Internal version of pthread_create. See comment in
103 pt-internal.h. */
104int
105__pthread_create_internal (struct __pthread **thread,
106 const pthread_attr_t * attr,
107 void *(*start_routine) (void *), void *arg)
108{
109 int err;
110 struct __pthread *pthread;
111 const struct __pthread_attr *setup;
112 sigset_t sigset;
113 size_t stacksize;
114
115 /* Avoid a data race in the multi-threaded case. */
116 if (__libc_single_threaded)
117 __libc_single_threaded = 0;
118
119 /* Allocate a new thread structure. */
120 err = __pthread_alloc (thread: &pthread);
121 if (err)
122 goto failed;
123
124 if (attr == ATTR_C11_THREAD)
125 {
126 attr = NULL;
127 pthread->c11 = true;
128 }
129 else
130 pthread->c11 = false;
131
132 /* Use the default attributes if ATTR is NULL. */
133 setup = attr ? attr : &__pthread_default_attr;
134
135 stacksize = setup->__stacksize;
136 if (stacksize == 0)
137 {
138 struct rlimit rlim;
139 __getrlimit (RLIMIT_STACK, &rlim);
140 if (rlim.rlim_cur != RLIM_INFINITY)
141 stacksize = rlim.rlim_cur;
142 if (stacksize == 0)
143 stacksize = PTHREAD_STACK_DEFAULT;
144 }
145
146 /* Initialize the thread state. */
147 pthread->state = (setup->__detachstate == PTHREAD_CREATE_DETACHED
148 ? PTHREAD_DETACHED : PTHREAD_JOINABLE);
149
150 if (setup->__stackaddr)
151 {
152 pthread->stackaddr = setup->__stackaddr;
153
154 /* If the user supplied a stack, it is not our responsibility to
155 setup a stack guard. */
156 pthread->guardsize = 0;
157 pthread->stack = 0;
158 }
159 else
160 {
161 /* Allocate a stack. */
162 err = __pthread_stack_alloc (&pthread->stackaddr,
163 ((setup->__guardsize + __vm_page_size - 1)
164 / __vm_page_size) * __vm_page_size
165 + stacksize);
166 if (err)
167 goto failed_stack_alloc;
168
169 pthread->guardsize = setup->__guardsize;
170 pthread->stack = 1;
171 }
172
173 pthread->stacksize = stacksize;
174
175 /* Allocate the kernel thread and other required resources. */
176 err = __pthread_thread_alloc (thread: pthread);
177 if (err)
178 goto failed_thread_alloc;
179
180 pthread->tcb = _dl_allocate_tls (NULL);
181 if (pthread->tcb == NULL)
182 {
183 err = ENOMEM;
184 goto failed_thread_tls_alloc;
185 }
186 pthread->tcb->tcb = pthread->tcb;
187
188 /* And initialize the rest of the machine context. This may include
189 additional machine- and system-specific initializations that
190 prove convenient. */
191 err = __pthread_setup (thread: pthread, entry_point, start_routine, arg);
192 if (err)
193 goto failed_setup;
194
195 /* Initialize the system-specific signal state for the new
196 thread. */
197 err = __pthread_sigstate_init (thread: pthread);
198 if (err)
199 goto failed_sigstate;
200
201 /* If the new thread is joinable, add a reference for the caller. */
202 if (pthread->state == PTHREAD_JOINABLE)
203 pthread->nr_refs++;
204
205 /* Set the new thread's signal mask and set the pending signals to
206 empty. POSIX says: "The signal mask shall be inherited from the
207 creating thread. The set of signals pending for the new thread
208 shall be empty." If the currnet thread is not a pthread then we
209 just inherit the process' sigmask. */
210 if (GL (dl_pthread_num_threads) == 1)
211 err = __sigprocmask (how: 0, set: 0, oset: &pthread->init_sigset);
212 else
213 err = __pthread_sigstate (thread: _pthread_self (), how: 0, set: 0, oset: &pthread->init_sigset, clear_pending: 0);
214 assert_perror (err);
215
216 if (start_routine)
217 /* But block the signals for now, until the thread is fully initialized. */
218 __sigfillset (set: &sigset);
219 else
220 sigset = pthread->init_sigset;
221 err = __pthread_sigstate (thread: pthread, SIG_SETMASK, set: &sigset, oset: 0, clear_pending: 1);
222 assert_perror (err);
223
224 /* Increase the total number of threads. We do this before actually
225 starting the new thread, since the new thread might immediately
226 call `pthread_exit' which decreases the number of threads and
227 calls `exit' if the number of threads reaches zero. Increasing
228 the number of threads from within the new thread isn't an option
229 since this thread might return and call `pthread_exit' before the
230 new thread runs. */
231 atomic_increment (&__pthread_total);
232
233 /* Store a pointer to this thread in the thread ID lookup table. We
234 could use __thread_setid, however, we only lock for reading as no
235 other thread should be using this entry (we also assume that the
236 store is atomic). */
237 __libc_rwlock_rdlock (GL (dl_pthread_threads_lock));
238 GL (dl_pthread_threads)[pthread->thread - 1] = pthread;
239 __libc_rwlock_unlock (GL (dl_pthread_threads_lock));
240
241 /* At this point it is possible to guess our pthread ID. We have to
242 make sure that all functions taking a pthread_t argument can
243 handle the fact that this thread isn't really running yet. Since
244 the new thread might be passed its ID through pthread_create (to
245 avoid calling pthread_self), read it before starting the thread. */
246 *thread = pthread;
247
248 /* Schedule the new thread. */
249 err = __pthread_thread_start (thread: pthread);
250 if (err)
251 goto failed_starting;
252
253
254 return 0;
255
256failed_starting:
257 /* If joinable, a reference was added for the caller. */
258 if (pthread->state == PTHREAD_JOINABLE)
259 {
260 __pthread_dealloc (thread: pthread);
261 __pthread_dealloc_finish (pthread);
262 }
263
264 __pthread_setid (pthread->thread, NULL);
265 atomic_decrement (&__pthread_total);
266failed_sigstate:
267 __pthread_sigstate_destroy (thread: pthread);
268failed_setup:
269 _dl_deallocate_tls (pthread->tcb, 1);
270 pthread->tcb = NULL;
271failed_thread_tls_alloc:
272 __pthread_thread_terminate (thread: pthread);
273
274 /* __pthread_thread_terminate has taken care of deallocating the stack and
275 the thread structure. */
276 goto failed;
277failed_thread_alloc:
278 if (pthread->stack)
279 __pthread_stack_dealloc (pthread->stackaddr,
280 ((setup->__guardsize + __vm_page_size - 1)
281 / __vm_page_size) * __vm_page_size + stacksize);
282failed_stack_alloc:
283 __pthread_dealloc (thread: pthread);
284 __pthread_dealloc_finish (pthread);
285failed:
286 return err;
287}
288

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