xref: /freebsd/lib/libthr/thread/thr_init.c (revision db612abe8df3355d1eb23bb3b50fdd97bc21e979)
1 /*
2  * Copyright (c) 2003 Daniel M. Eischen <deischen@freebsd.org>
3  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
4  * All rights reserved.
5  *
6  * Redistribution and use in source and binary forms, with or without
7  * modification, are permitted provided that the following conditions
8  * are met:
9  * 1. Redistributions of source code must retain the above copyright
10  *    notice, this list of conditions and the following disclaimer.
11  * 2. Redistributions in binary form must reproduce the above copyright
12  *    notice, this list of conditions and the following disclaimer in the
13  *    documentation and/or other materials provided with the distribution.
14  * 3. All advertising materials mentioning features or use of this software
15  *    must display the following acknowledgement:
16  *	This product includes software developed by John Birrell.
17  * 4. Neither the name of the author nor the names of any co-contributors
18  *    may be used to endorse or promote products derived from this software
19  *    without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
22  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
25  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31  * SUCH DAMAGE.
32  *
33  * $FreeBSD$
34  */
35 
36 #include "namespace.h"
37 #include <sys/types.h>
38 #include <sys/signalvar.h>
39 #include <sys/ioctl.h>
40 #include <sys/sysctl.h>
41 #include <sys/ttycom.h>
42 #include <sys/mman.h>
43 #include <sys/rtprio.h>
44 #include <errno.h>
45 #include <fcntl.h>
46 #include <paths.h>
47 #include <pthread.h>
48 #include <pthread_np.h>
49 #include <signal.h>
50 #include <stdlib.h>
51 #include <string.h>
52 #include <time.h>
53 #include <unistd.h>
54 #include "un-namespace.h"
55 
56 #include "libc_private.h"
57 #include "thr_private.h"
58 
59 char		*_usrstack;
60 struct pthread	*_thr_initial;
61 int		_libthr_debug;
62 int		_thread_event_mask;
63 struct pthread	*_thread_last_event;
64 pthreadlist	_thread_list = TAILQ_HEAD_INITIALIZER(_thread_list);
65 pthreadlist 	_thread_gc_list = TAILQ_HEAD_INITIALIZER(_thread_gc_list);
66 int		_thread_active_threads = 1;
67 atfork_head	_thr_atfork_list = TAILQ_HEAD_INITIALIZER(_thr_atfork_list);
68 struct umutex	_thr_atfork_lock = DEFAULT_UMUTEX;
69 
70 struct pthread_prio	_thr_priorities[3] = {
71 	{RTP_PRIO_MIN,  RTP_PRIO_MAX, 0}, /* FIFO */
72 	{0, 0, 63}, /* OTHER */
73 	{RTP_PRIO_MIN, RTP_PRIO_MAX, 0}  /* RR */
74 };
75 
76 struct pthread_attr _pthread_attr_default = {
77 	.sched_policy = SCHED_OTHER,
78 	.sched_inherit = PTHREAD_INHERIT_SCHED,
79 	.prio = 0,
80 	.suspend = THR_CREATE_RUNNING,
81 	.flags = PTHREAD_SCOPE_SYSTEM,
82 	.stackaddr_attr = NULL,
83 	.stacksize_attr = THR_STACK_DEFAULT,
84 	.guardsize_attr = 0,
85 	.cpusetsize = 0,
86 	.cpuset = NULL
87 };
88 
89 struct pthread_mutex_attr _pthread_mutexattr_default = {
90 	.m_type = PTHREAD_MUTEX_DEFAULT,
91 	.m_protocol = PTHREAD_PRIO_NONE,
92 	.m_ceiling = 0,
93 	.m_flags = 0
94 };
95 
96 /* Default condition variable attributes: */
97 struct pthread_cond_attr _pthread_condattr_default = {
98 	.c_pshared = PTHREAD_PROCESS_PRIVATE,
99 	.c_clockid = CLOCK_REALTIME
100 };
101 
102 pid_t		_thr_pid;
103 int		_thr_is_smp = 0;
104 size_t		_thr_guard_default;
105 size_t		_thr_stack_default = THR_STACK_DEFAULT;
106 size_t		_thr_stack_initial = THR_STACK_INITIAL;
107 int		_thr_page_size;
108 int		_thr_spinloops;
109 int		_thr_yieldloops;
110 int		_gc_count;
111 struct umutex	_mutex_static_lock = DEFAULT_UMUTEX;
112 struct umutex	_cond_static_lock = DEFAULT_UMUTEX;
113 struct umutex	_rwlock_static_lock = DEFAULT_UMUTEX;
114 struct umutex	_keytable_lock = DEFAULT_UMUTEX;
115 struct umutex	_thr_list_lock = DEFAULT_UMUTEX;
116 struct umutex	_thr_event_lock = DEFAULT_UMUTEX;
117 
118 int	__pthread_cond_wait(pthread_cond_t *, pthread_mutex_t *);
119 int	__pthread_mutex_lock(pthread_mutex_t *);
120 int	__pthread_mutex_trylock(pthread_mutex_t *);
121 void	_thread_init_hack(void) __attribute__ ((constructor));
122 
123 static void init_private(void);
124 static void init_main_thread(struct pthread *thread);
125 
126 /*
127  * All weak references used within libc should be in this table.
128  * This is so that static libraries will work.
129  */
130 
131 STATIC_LIB_REQUIRE(_fork);
132 STATIC_LIB_REQUIRE(_pthread_getspecific);
133 STATIC_LIB_REQUIRE(_pthread_key_create);
134 STATIC_LIB_REQUIRE(_pthread_key_delete);
135 STATIC_LIB_REQUIRE(_pthread_mutex_destroy);
136 STATIC_LIB_REQUIRE(_pthread_mutex_init);
137 STATIC_LIB_REQUIRE(_pthread_mutex_lock);
138 STATIC_LIB_REQUIRE(_pthread_mutex_trylock);
139 STATIC_LIB_REQUIRE(_pthread_mutex_unlock);
140 STATIC_LIB_REQUIRE(_pthread_mutexattr_init);
141 STATIC_LIB_REQUIRE(_pthread_mutexattr_destroy);
142 STATIC_LIB_REQUIRE(_pthread_mutexattr_settype);
143 STATIC_LIB_REQUIRE(_pthread_once);
144 STATIC_LIB_REQUIRE(_pthread_setspecific);
145 STATIC_LIB_REQUIRE(_raise);
146 STATIC_LIB_REQUIRE(_sem_destroy);
147 STATIC_LIB_REQUIRE(_sem_getvalue);
148 STATIC_LIB_REQUIRE(_sem_init);
149 STATIC_LIB_REQUIRE(_sem_post);
150 STATIC_LIB_REQUIRE(_sem_timedwait);
151 STATIC_LIB_REQUIRE(_sem_trywait);
152 STATIC_LIB_REQUIRE(_sem_wait);
153 STATIC_LIB_REQUIRE(_sigaction);
154 STATIC_LIB_REQUIRE(_sigprocmask);
155 STATIC_LIB_REQUIRE(_sigsuspend);
156 STATIC_LIB_REQUIRE(_sigtimedwait);
157 STATIC_LIB_REQUIRE(_sigwait);
158 STATIC_LIB_REQUIRE(_sigwaitinfo);
159 STATIC_LIB_REQUIRE(_spinlock);
160 STATIC_LIB_REQUIRE(_spinlock_debug);
161 STATIC_LIB_REQUIRE(_spinunlock);
162 STATIC_LIB_REQUIRE(_thread_init_hack);
163 
164 /*
165  * These are needed when linking statically.  All references within
166  * libgcc (and in the future libc) to these routines are weak, but
167  * if they are not (strongly) referenced by the application or other
168  * libraries, then the actual functions will not be loaded.
169  */
170 STATIC_LIB_REQUIRE(_pthread_once);
171 STATIC_LIB_REQUIRE(_pthread_key_create);
172 STATIC_LIB_REQUIRE(_pthread_key_delete);
173 STATIC_LIB_REQUIRE(_pthread_getspecific);
174 STATIC_LIB_REQUIRE(_pthread_setspecific);
175 STATIC_LIB_REQUIRE(_pthread_mutex_init);
176 STATIC_LIB_REQUIRE(_pthread_mutex_destroy);
177 STATIC_LIB_REQUIRE(_pthread_mutex_lock);
178 STATIC_LIB_REQUIRE(_pthread_mutex_trylock);
179 STATIC_LIB_REQUIRE(_pthread_mutex_unlock);
180 STATIC_LIB_REQUIRE(_pthread_create);
181 
182 /* Pull in all symbols required by libthread_db */
183 STATIC_LIB_REQUIRE(_thread_state_running);
184 
185 #define	DUAL_ENTRY(entry)	\
186 	(pthread_func_t)entry, (pthread_func_t)entry
187 
188 static pthread_func_t jmp_table[][2] = {
189 	{DUAL_ENTRY(_pthread_atfork)},	/* PJT_ATFORK */
190 	{DUAL_ENTRY(_pthread_attr_destroy)},	/* PJT_ATTR_DESTROY */
191 	{DUAL_ENTRY(_pthread_attr_getdetachstate)},	/* PJT_ATTR_GETDETACHSTATE */
192 	{DUAL_ENTRY(_pthread_attr_getguardsize)},	/* PJT_ATTR_GETGUARDSIZE */
193 	{DUAL_ENTRY(_pthread_attr_getinheritsched)},	/* PJT_ATTR_GETINHERITSCHED */
194 	{DUAL_ENTRY(_pthread_attr_getschedparam)},	/* PJT_ATTR_GETSCHEDPARAM */
195 	{DUAL_ENTRY(_pthread_attr_getschedpolicy)},	/* PJT_ATTR_GETSCHEDPOLICY */
196 	{DUAL_ENTRY(_pthread_attr_getscope)},	/* PJT_ATTR_GETSCOPE */
197 	{DUAL_ENTRY(_pthread_attr_getstackaddr)},	/* PJT_ATTR_GETSTACKADDR */
198 	{DUAL_ENTRY(_pthread_attr_getstacksize)},	/* PJT_ATTR_GETSTACKSIZE */
199 	{DUAL_ENTRY(_pthread_attr_init)},	/* PJT_ATTR_INIT */
200 	{DUAL_ENTRY(_pthread_attr_setdetachstate)},	/* PJT_ATTR_SETDETACHSTATE */
201 	{DUAL_ENTRY(_pthread_attr_setguardsize)},	/* PJT_ATTR_SETGUARDSIZE */
202 	{DUAL_ENTRY(_pthread_attr_setinheritsched)},	/* PJT_ATTR_SETINHERITSCHED */
203 	{DUAL_ENTRY(_pthread_attr_setschedparam)},	/* PJT_ATTR_SETSCHEDPARAM */
204 	{DUAL_ENTRY(_pthread_attr_setschedpolicy)},	/* PJT_ATTR_SETSCHEDPOLICY */
205 	{DUAL_ENTRY(_pthread_attr_setscope)},	/* PJT_ATTR_SETSCOPE */
206 	{DUAL_ENTRY(_pthread_attr_setstackaddr)},	/* PJT_ATTR_SETSTACKADDR */
207 	{DUAL_ENTRY(_pthread_attr_setstacksize)},	/* PJT_ATTR_SETSTACKSIZE */
208 	{DUAL_ENTRY(_pthread_cancel)},	/* PJT_CANCEL */
209 	{DUAL_ENTRY(_pthread_cleanup_pop)},	/* PJT_CLEANUP_POP */
210 	{DUAL_ENTRY(_pthread_cleanup_push)},	/* PJT_CLEANUP_PUSH */
211 	{DUAL_ENTRY(_pthread_cond_broadcast)},	/* PJT_COND_BROADCAST */
212 	{DUAL_ENTRY(_pthread_cond_destroy)},	/* PJT_COND_DESTROY */
213 	{DUAL_ENTRY(_pthread_cond_init)},	/* PJT_COND_INIT */
214 	{DUAL_ENTRY(_pthread_cond_signal)},	/* PJT_COND_SIGNAL */
215 	{DUAL_ENTRY(_pthread_cond_timedwait)},	/* PJT_COND_TIMEDWAIT */
216 	{(pthread_func_t)__pthread_cond_wait,
217 	 (pthread_func_t)_pthread_cond_wait},	/* PJT_COND_WAIT */
218 	{DUAL_ENTRY(_pthread_detach)},	/* PJT_DETACH */
219 	{DUAL_ENTRY(_pthread_equal)},	/* PJT_EQUAL */
220 	{DUAL_ENTRY(_pthread_exit)},	/* PJT_EXIT */
221 	{DUAL_ENTRY(_pthread_getspecific)},	/* PJT_GETSPECIFIC */
222 	{DUAL_ENTRY(_pthread_join)},	/* PJT_JOIN */
223 	{DUAL_ENTRY(_pthread_key_create)},	/* PJT_KEY_CREATE */
224 	{DUAL_ENTRY(_pthread_key_delete)},	/* PJT_KEY_DELETE*/
225 	{DUAL_ENTRY(_pthread_kill)},	/* PJT_KILL */
226 	{DUAL_ENTRY(_pthread_main_np)},		/* PJT_MAIN_NP */
227 	{DUAL_ENTRY(_pthread_mutexattr_destroy)}, /* PJT_MUTEXATTR_DESTROY */
228 	{DUAL_ENTRY(_pthread_mutexattr_init)},	/* PJT_MUTEXATTR_INIT */
229 	{DUAL_ENTRY(_pthread_mutexattr_settype)}, /* PJT_MUTEXATTR_SETTYPE */
230 	{DUAL_ENTRY(_pthread_mutex_destroy)},	/* PJT_MUTEX_DESTROY */
231 	{DUAL_ENTRY(_pthread_mutex_init)},	/* PJT_MUTEX_INIT */
232 	{(pthread_func_t)__pthread_mutex_lock,
233 	 (pthread_func_t)_pthread_mutex_lock},	/* PJT_MUTEX_LOCK */
234 	{(pthread_func_t)__pthread_mutex_trylock,
235 	 (pthread_func_t)_pthread_mutex_trylock},/* PJT_MUTEX_TRYLOCK */
236 	{DUAL_ENTRY(_pthread_mutex_unlock)},	/* PJT_MUTEX_UNLOCK */
237 	{DUAL_ENTRY(_pthread_once)},		/* PJT_ONCE */
238 	{DUAL_ENTRY(_pthread_rwlock_destroy)},	/* PJT_RWLOCK_DESTROY */
239 	{DUAL_ENTRY(_pthread_rwlock_init)},	/* PJT_RWLOCK_INIT */
240 	{DUAL_ENTRY(_pthread_rwlock_rdlock)},	/* PJT_RWLOCK_RDLOCK */
241 	{DUAL_ENTRY(_pthread_rwlock_tryrdlock)},/* PJT_RWLOCK_TRYRDLOCK */
242 	{DUAL_ENTRY(_pthread_rwlock_trywrlock)},/* PJT_RWLOCK_TRYWRLOCK */
243 	{DUAL_ENTRY(_pthread_rwlock_unlock)},	/* PJT_RWLOCK_UNLOCK */
244 	{DUAL_ENTRY(_pthread_rwlock_wrlock)},	/* PJT_RWLOCK_WRLOCK */
245 	{DUAL_ENTRY(_pthread_self)},		/* PJT_SELF */
246 	{DUAL_ENTRY(_pthread_setcancelstate)},	/* PJT_SETCANCELSTATE */
247 	{DUAL_ENTRY(_pthread_setcanceltype)},	/* PJT_SETCANCELTYPE */
248 	{DUAL_ENTRY(_pthread_setspecific)},	/* PJT_SETSPECIFIC */
249 	{DUAL_ENTRY(_pthread_sigmask)},		/* PJT_SIGMASK */
250 	{DUAL_ENTRY(_pthread_testcancel)}	/* PJT_TESTCANCEL */
251 };
252 
253 static int init_once = 0;
254 
255 /*
256  * For the shared version of the threads library, the above is sufficient.
257  * But for the archive version of the library, we need a little bit more.
258  * Namely, we must arrange for this particular module to be pulled in from
259  * the archive library at link time.  To accomplish that, we define and
260  * initialize a variable, "_thread_autoinit_dummy_decl".  This variable is
261  * referenced (as an extern) from libc/stdlib/exit.c. This will always
262  * create a need for this module, ensuring that it is present in the
263  * executable.
264  */
265 extern int _thread_autoinit_dummy_decl;
266 int _thread_autoinit_dummy_decl = 0;
267 
268 void
269 _thread_init_hack(void)
270 {
271 
272 	_libpthread_init(NULL);
273 }
274 
275 
276 /*
277  * Threaded process initialization.
278  *
279  * This is only called under two conditions:
280  *
281  *   1) Some thread routines have detected that the library hasn't yet
282  *      been initialized (_thr_initial == NULL && curthread == NULL), or
283  *
284  *   2) An explicit call to reinitialize after a fork (indicated
285  *      by curthread != NULL)
286  */
287 void
288 _libpthread_init(struct pthread *curthread)
289 {
290 	int fd, first = 0;
291 	sigset_t sigset, oldset;
292 
293 	/* Check if this function has already been called: */
294 	if ((_thr_initial != NULL) && (curthread == NULL))
295 		/* Only initialize the threaded application once. */
296 		return;
297 
298 	/*
299 	 * Check the size of the jump table to make sure it is preset
300 	 * with the correct number of entries.
301 	 */
302 	if (sizeof(jmp_table) != (sizeof(pthread_func_t) * PJT_MAX * 2))
303 		PANIC("Thread jump table not properly initialized");
304 	memcpy(__thr_jtable, jmp_table, sizeof(jmp_table));
305 
306 	/*
307 	 * Check for the special case of this process running as
308 	 * or in place of init as pid = 1:
309 	 */
310 	if ((_thr_pid = getpid()) == 1) {
311 		/*
312 		 * Setup a new session for this process which is
313 		 * assumed to be running as root.
314 		 */
315 		if (setsid() == -1)
316 			PANIC("Can't set session ID");
317 		if (revoke(_PATH_CONSOLE) != 0)
318 			PANIC("Can't revoke console");
319 		if ((fd = __sys_open(_PATH_CONSOLE, O_RDWR)) < 0)
320 			PANIC("Can't open console");
321 		if (setlogin("root") == -1)
322 			PANIC("Can't set login to root");
323 		if (_ioctl(fd, TIOCSCTTY, (char *) NULL) == -1)
324 			PANIC("Can't set controlling terminal");
325 	}
326 
327 	/* Initialize pthread private data. */
328 	init_private();
329 
330 	/* Set the initial thread. */
331 	if (curthread == NULL) {
332 		first = 1;
333 		/* Create and initialize the initial thread. */
334 		curthread = _thr_alloc(NULL);
335 		if (curthread == NULL)
336 			PANIC("Can't allocate initial thread");
337 		init_main_thread(curthread);
338 	}
339 	/*
340 	 * Add the thread to the thread list queue.
341 	 */
342 	THR_LIST_ADD(curthread);
343 	_thread_active_threads = 1;
344 
345 	/* Setup the thread specific data */
346 	_tcb_set(curthread->tcb);
347 
348 	if (first) {
349 		SIGFILLSET(sigset);
350 		SIGDELSET(sigset, SIGTRAP);
351 		__sys_sigprocmask(SIG_SETMASK, &sigset, &oldset);
352 		_thr_signal_init();
353 		_thr_initial = curthread;
354 		SIGDELSET(oldset, SIGCANCEL);
355 		__sys_sigprocmask(SIG_SETMASK, &oldset, NULL);
356 		if (_thread_event_mask & TD_CREATE)
357 			_thr_report_creation(curthread, curthread);
358 	}
359 }
360 
361 /*
362  * This function and pthread_create() do a lot of the same things.
363  * It'd be nice to consolidate the common stuff in one place.
364  */
365 static void
366 init_main_thread(struct pthread *thread)
367 {
368 	struct sched_param sched_param;
369 
370 	/* Setup the thread attributes. */
371 	thr_self(&thread->tid);
372 	thread->attr = _pthread_attr_default;
373 	/*
374 	 * Set up the thread stack.
375 	 *
376 	 * Create a red zone below the main stack.  All other stacks
377 	 * are constrained to a maximum size by the parameters
378 	 * passed to mmap(), but this stack is only limited by
379 	 * resource limits, so this stack needs an explicitly mapped
380 	 * red zone to protect the thread stack that is just beyond.
381 	 */
382 	if (mmap(_usrstack - _thr_stack_initial -
383 	    _thr_guard_default, _thr_guard_default, 0, MAP_ANON,
384 	    -1, 0) == MAP_FAILED)
385 		PANIC("Cannot allocate red zone for initial thread");
386 
387 	/*
388 	 * Mark the stack as an application supplied stack so that it
389 	 * isn't deallocated.
390 	 *
391 	 * XXX - I'm not sure it would hurt anything to deallocate
392 	 *       the main thread stack because deallocation doesn't
393 	 *       actually free() it; it just puts it in the free
394 	 *       stack queue for later reuse.
395 	 */
396 	thread->attr.stackaddr_attr = _usrstack - _thr_stack_initial;
397 	thread->attr.stacksize_attr = _thr_stack_initial;
398 	thread->attr.guardsize_attr = _thr_guard_default;
399 	thread->attr.flags |= THR_STACK_USER;
400 
401 	/*
402 	 * Write a magic value to the thread structure
403 	 * to help identify valid ones:
404 	 */
405 	thread->magic = THR_MAGIC;
406 
407 	thread->cancel_enable = 1;
408 	thread->cancel_async = 0;
409 	thr_set_name(thread->tid, "initial thread");
410 
411 	/* Initialize the mutex queue: */
412 	TAILQ_INIT(&thread->mutexq);
413 	TAILQ_INIT(&thread->pp_mutexq);
414 
415 	thread->state = PS_RUNNING;
416 
417 	_thr_getscheduler(thread->tid, &thread->attr.sched_policy,
418 		 &sched_param);
419 	thread->attr.prio = sched_param.sched_priority;
420 
421 	/* Others cleared to zero by thr_alloc() */
422 }
423 
424 static void
425 init_private(void)
426 {
427 	size_t len;
428 	int mib[2];
429 	char *env;
430 
431 	_thr_umutex_init(&_mutex_static_lock);
432 	_thr_umutex_init(&_cond_static_lock);
433 	_thr_umutex_init(&_rwlock_static_lock);
434 	_thr_umutex_init(&_keytable_lock);
435 	_thr_umutex_init(&_thr_atfork_lock);
436 	_thr_umutex_init(&_thr_event_lock);
437 	_thr_once_init();
438 	_thr_spinlock_init();
439 	_thr_list_init();
440 
441 	/*
442 	 * Avoid reinitializing some things if they don't need to be,
443 	 * e.g. after a fork().
444 	 */
445 	if (init_once == 0) {
446 		/* Find the stack top */
447 		mib[0] = CTL_KERN;
448 		mib[1] = KERN_USRSTACK;
449 		len = sizeof (_usrstack);
450 		if (sysctl(mib, 2, &_usrstack, &len, NULL, 0) == -1)
451 			PANIC("Cannot get kern.usrstack from sysctl");
452 		len = sizeof(_thr_is_smp);
453 		sysctlbyname("kern.smp.cpus", &_thr_is_smp, &len, NULL, 0);
454 		_thr_is_smp = (_thr_is_smp > 1);
455 		_thr_page_size = getpagesize();
456 		_thr_guard_default = _thr_page_size;
457 		_pthread_attr_default.guardsize_attr = _thr_guard_default;
458 		_pthread_attr_default.stacksize_attr = _thr_stack_default;
459 		env = getenv("LIBPTHREAD_SPINLOOPS");
460 		if (env)
461 			_thr_spinloops = atoi(env);
462 		env = getenv("LIBPTHREAD_YIELDLOOPS");
463 		if (env)
464 			_thr_yieldloops = atoi(env);
465 		TAILQ_INIT(&_thr_atfork_list);
466 	}
467 	init_once = 1;
468 }
469