xref: /freebsd/lib/libthr/thread/thr_init.c (revision 480f4e946db51c7de558c4cd1ba3d88caeaceec8)
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/link_elf.h>
41 #include <sys/resource.h>
42 #include <sys/sysctl.h>
43 #include <sys/ttycom.h>
44 #include <sys/mman.h>
45 #include <sys/rtprio.h>
46 #include <errno.h>
47 #include <fcntl.h>
48 #include <paths.h>
49 #include <pthread.h>
50 #include <pthread_np.h>
51 #include <signal.h>
52 #include <stdlib.h>
53 #include <string.h>
54 #include <time.h>
55 #include <unistd.h>
56 #include "un-namespace.h"
57 
58 #include "libc_private.h"
59 #include "thr_private.h"
60 
61 char		*_usrstack;
62 struct pthread	*_thr_initial;
63 int		_libthr_debug;
64 int		_thread_event_mask;
65 struct pthread	*_thread_last_event;
66 pthreadlist	_thread_list = TAILQ_HEAD_INITIALIZER(_thread_list);
67 pthreadlist 	_thread_gc_list = TAILQ_HEAD_INITIALIZER(_thread_gc_list);
68 int		_thread_active_threads = 1;
69 atfork_head	_thr_atfork_list = TAILQ_HEAD_INITIALIZER(_thr_atfork_list);
70 struct urwlock	_thr_atfork_lock = DEFAULT_URWLOCK;
71 
72 struct pthread_prio	_thr_priorities[3] = {
73 	{RTP_PRIO_MIN,  RTP_PRIO_MAX, 0}, /* FIFO */
74 	{0, 0, 63}, /* OTHER */
75 	{RTP_PRIO_MIN, RTP_PRIO_MAX, 0}  /* RR */
76 };
77 
78 struct pthread_attr _pthread_attr_default = {
79 	.sched_policy = SCHED_OTHER,
80 	.sched_inherit = PTHREAD_INHERIT_SCHED,
81 	.prio = 0,
82 	.suspend = THR_CREATE_RUNNING,
83 	.flags = PTHREAD_SCOPE_SYSTEM,
84 	.stackaddr_attr = NULL,
85 	.stacksize_attr = THR_STACK_DEFAULT,
86 	.guardsize_attr = 0,
87 	.cpusetsize = 0,
88 	.cpuset = NULL
89 };
90 
91 struct pthread_mutex_attr _pthread_mutexattr_default = {
92 	.m_type = PTHREAD_MUTEX_DEFAULT,
93 	.m_protocol = PTHREAD_PRIO_NONE,
94 	.m_ceiling = 0,
95 	.m_pshared = PTHREAD_PROCESS_PRIVATE,
96 };
97 
98 struct pthread_mutex_attr _pthread_mutexattr_adaptive_default = {
99 	.m_type = PTHREAD_MUTEX_ADAPTIVE_NP,
100 	.m_protocol = PTHREAD_PRIO_NONE,
101 	.m_ceiling = 0,
102 	.m_pshared = PTHREAD_PROCESS_PRIVATE,
103 };
104 
105 /* Default condition variable attributes: */
106 struct pthread_cond_attr _pthread_condattr_default = {
107 	.c_pshared = PTHREAD_PROCESS_PRIVATE,
108 	.c_clockid = CLOCK_REALTIME
109 };
110 
111 pid_t		_thr_pid;
112 int		_thr_is_smp = 0;
113 size_t		_thr_guard_default;
114 size_t		_thr_stack_default = THR_STACK_DEFAULT;
115 size_t		_thr_stack_initial = THR_STACK_INITIAL;
116 int		_thr_page_size;
117 int		_thr_spinloops;
118 int		_thr_yieldloops;
119 int		_thr_queuefifo = 4;
120 int		_gc_count;
121 struct umutex	_mutex_static_lock = DEFAULT_UMUTEX;
122 struct umutex	_cond_static_lock = DEFAULT_UMUTEX;
123 struct umutex	_rwlock_static_lock = DEFAULT_UMUTEX;
124 struct umutex	_keytable_lock = DEFAULT_UMUTEX;
125 struct urwlock	_thr_list_lock = DEFAULT_URWLOCK;
126 struct umutex	_thr_event_lock = DEFAULT_UMUTEX;
127 struct umutex	_suspend_all_lock = DEFAULT_UMUTEX;
128 struct pthread	*_single_thread;
129 int		_suspend_all_cycle;
130 int		_suspend_all_waiters;
131 
132 int	__pthread_cond_wait(pthread_cond_t *, pthread_mutex_t *);
133 int	__pthread_mutex_lock(pthread_mutex_t *);
134 int	__pthread_mutex_trylock(pthread_mutex_t *);
135 void	_thread_init_hack(void) __attribute__ ((constructor));
136 
137 static void init_private(void);
138 static void init_main_thread(struct pthread *thread);
139 
140 /*
141  * All weak references used within libc should be in this table.
142  * This is so that static libraries will work.
143  */
144 
145 STATIC_LIB_REQUIRE(_fork);
146 STATIC_LIB_REQUIRE(_pthread_getspecific);
147 STATIC_LIB_REQUIRE(_pthread_key_create);
148 STATIC_LIB_REQUIRE(_pthread_key_delete);
149 STATIC_LIB_REQUIRE(_pthread_mutex_destroy);
150 STATIC_LIB_REQUIRE(_pthread_mutex_init);
151 STATIC_LIB_REQUIRE(_pthread_mutex_lock);
152 STATIC_LIB_REQUIRE(_pthread_mutex_trylock);
153 STATIC_LIB_REQUIRE(_pthread_mutex_unlock);
154 STATIC_LIB_REQUIRE(_pthread_mutexattr_init);
155 STATIC_LIB_REQUIRE(_pthread_mutexattr_destroy);
156 STATIC_LIB_REQUIRE(_pthread_mutexattr_settype);
157 STATIC_LIB_REQUIRE(_pthread_once);
158 STATIC_LIB_REQUIRE(_pthread_setspecific);
159 STATIC_LIB_REQUIRE(_raise);
160 STATIC_LIB_REQUIRE(_sem_destroy);
161 STATIC_LIB_REQUIRE(_sem_getvalue);
162 STATIC_LIB_REQUIRE(_sem_init);
163 STATIC_LIB_REQUIRE(_sem_post);
164 STATIC_LIB_REQUIRE(_sem_timedwait);
165 STATIC_LIB_REQUIRE(_sem_trywait);
166 STATIC_LIB_REQUIRE(_sem_wait);
167 STATIC_LIB_REQUIRE(_sigaction);
168 STATIC_LIB_REQUIRE(_sigprocmask);
169 STATIC_LIB_REQUIRE(_sigsuspend);
170 STATIC_LIB_REQUIRE(_sigtimedwait);
171 STATIC_LIB_REQUIRE(_sigwait);
172 STATIC_LIB_REQUIRE(_sigwaitinfo);
173 STATIC_LIB_REQUIRE(_spinlock);
174 STATIC_LIB_REQUIRE(_spinlock_debug);
175 STATIC_LIB_REQUIRE(_spinunlock);
176 STATIC_LIB_REQUIRE(_thread_init_hack);
177 
178 /*
179  * These are needed when linking statically.  All references within
180  * libgcc (and in the future libc) to these routines are weak, but
181  * if they are not (strongly) referenced by the application or other
182  * libraries, then the actual functions will not be loaded.
183  */
184 STATIC_LIB_REQUIRE(_pthread_once);
185 STATIC_LIB_REQUIRE(_pthread_key_create);
186 STATIC_LIB_REQUIRE(_pthread_key_delete);
187 STATIC_LIB_REQUIRE(_pthread_getspecific);
188 STATIC_LIB_REQUIRE(_pthread_setspecific);
189 STATIC_LIB_REQUIRE(_pthread_mutex_init);
190 STATIC_LIB_REQUIRE(_pthread_mutex_destroy);
191 STATIC_LIB_REQUIRE(_pthread_mutex_lock);
192 STATIC_LIB_REQUIRE(_pthread_mutex_trylock);
193 STATIC_LIB_REQUIRE(_pthread_mutex_unlock);
194 STATIC_LIB_REQUIRE(_pthread_create);
195 
196 /* Pull in all symbols required by libthread_db */
197 STATIC_LIB_REQUIRE(_thread_state_running);
198 
199 #define	DUAL_ENTRY(entry)	\
200 	(pthread_func_t)entry, (pthread_func_t)entry
201 
202 static pthread_func_t jmp_table[][2] = {
203 	{DUAL_ENTRY(_pthread_atfork)},	/* PJT_ATFORK */
204 	{DUAL_ENTRY(_pthread_attr_destroy)},	/* PJT_ATTR_DESTROY */
205 	{DUAL_ENTRY(_pthread_attr_getdetachstate)},	/* PJT_ATTR_GETDETACHSTATE */
206 	{DUAL_ENTRY(_pthread_attr_getguardsize)},	/* PJT_ATTR_GETGUARDSIZE */
207 	{DUAL_ENTRY(_pthread_attr_getinheritsched)},	/* PJT_ATTR_GETINHERITSCHED */
208 	{DUAL_ENTRY(_pthread_attr_getschedparam)},	/* PJT_ATTR_GETSCHEDPARAM */
209 	{DUAL_ENTRY(_pthread_attr_getschedpolicy)},	/* PJT_ATTR_GETSCHEDPOLICY */
210 	{DUAL_ENTRY(_pthread_attr_getscope)},	/* PJT_ATTR_GETSCOPE */
211 	{DUAL_ENTRY(_pthread_attr_getstackaddr)},	/* PJT_ATTR_GETSTACKADDR */
212 	{DUAL_ENTRY(_pthread_attr_getstacksize)},	/* PJT_ATTR_GETSTACKSIZE */
213 	{DUAL_ENTRY(_pthread_attr_init)},	/* PJT_ATTR_INIT */
214 	{DUAL_ENTRY(_pthread_attr_setdetachstate)},	/* PJT_ATTR_SETDETACHSTATE */
215 	{DUAL_ENTRY(_pthread_attr_setguardsize)},	/* PJT_ATTR_SETGUARDSIZE */
216 	{DUAL_ENTRY(_pthread_attr_setinheritsched)},	/* PJT_ATTR_SETINHERITSCHED */
217 	{DUAL_ENTRY(_pthread_attr_setschedparam)},	/* PJT_ATTR_SETSCHEDPARAM */
218 	{DUAL_ENTRY(_pthread_attr_setschedpolicy)},	/* PJT_ATTR_SETSCHEDPOLICY */
219 	{DUAL_ENTRY(_pthread_attr_setscope)},	/* PJT_ATTR_SETSCOPE */
220 	{DUAL_ENTRY(_pthread_attr_setstackaddr)},	/* PJT_ATTR_SETSTACKADDR */
221 	{DUAL_ENTRY(_pthread_attr_setstacksize)},	/* PJT_ATTR_SETSTACKSIZE */
222 	{DUAL_ENTRY(_pthread_cancel)},	/* PJT_CANCEL */
223 	{DUAL_ENTRY(_pthread_cleanup_pop)},	/* PJT_CLEANUP_POP */
224 	{DUAL_ENTRY(_pthread_cleanup_push)},	/* PJT_CLEANUP_PUSH */
225 	{DUAL_ENTRY(_pthread_cond_broadcast)},	/* PJT_COND_BROADCAST */
226 	{DUAL_ENTRY(_pthread_cond_destroy)},	/* PJT_COND_DESTROY */
227 	{DUAL_ENTRY(_pthread_cond_init)},	/* PJT_COND_INIT */
228 	{DUAL_ENTRY(_pthread_cond_signal)},	/* PJT_COND_SIGNAL */
229 	{DUAL_ENTRY(_pthread_cond_timedwait)},	/* PJT_COND_TIMEDWAIT */
230 	{(pthread_func_t)__pthread_cond_wait,
231 	 (pthread_func_t)_pthread_cond_wait},	/* PJT_COND_WAIT */
232 	{DUAL_ENTRY(_pthread_detach)},	/* PJT_DETACH */
233 	{DUAL_ENTRY(_pthread_equal)},	/* PJT_EQUAL */
234 	{DUAL_ENTRY(_pthread_exit)},	/* PJT_EXIT */
235 	{DUAL_ENTRY(_pthread_getspecific)},	/* PJT_GETSPECIFIC */
236 	{DUAL_ENTRY(_pthread_join)},	/* PJT_JOIN */
237 	{DUAL_ENTRY(_pthread_key_create)},	/* PJT_KEY_CREATE */
238 	{DUAL_ENTRY(_pthread_key_delete)},	/* PJT_KEY_DELETE*/
239 	{DUAL_ENTRY(_pthread_kill)},	/* PJT_KILL */
240 	{DUAL_ENTRY(_pthread_main_np)},		/* PJT_MAIN_NP */
241 	{DUAL_ENTRY(_pthread_mutexattr_destroy)}, /* PJT_MUTEXATTR_DESTROY */
242 	{DUAL_ENTRY(_pthread_mutexattr_init)},	/* PJT_MUTEXATTR_INIT */
243 	{DUAL_ENTRY(_pthread_mutexattr_settype)}, /* PJT_MUTEXATTR_SETTYPE */
244 	{DUAL_ENTRY(_pthread_mutex_destroy)},	/* PJT_MUTEX_DESTROY */
245 	{DUAL_ENTRY(_pthread_mutex_init)},	/* PJT_MUTEX_INIT */
246 	{(pthread_func_t)__pthread_mutex_lock,
247 	 (pthread_func_t)_pthread_mutex_lock},	/* PJT_MUTEX_LOCK */
248 	{(pthread_func_t)__pthread_mutex_trylock,
249 	 (pthread_func_t)_pthread_mutex_trylock},/* PJT_MUTEX_TRYLOCK */
250 	{DUAL_ENTRY(_pthread_mutex_unlock)},	/* PJT_MUTEX_UNLOCK */
251 	{DUAL_ENTRY(_pthread_once)},		/* PJT_ONCE */
252 	{DUAL_ENTRY(_pthread_rwlock_destroy)},	/* PJT_RWLOCK_DESTROY */
253 	{DUAL_ENTRY(_pthread_rwlock_init)},	/* PJT_RWLOCK_INIT */
254 	{DUAL_ENTRY(_pthread_rwlock_rdlock)},	/* PJT_RWLOCK_RDLOCK */
255 	{DUAL_ENTRY(_pthread_rwlock_tryrdlock)},/* PJT_RWLOCK_TRYRDLOCK */
256 	{DUAL_ENTRY(_pthread_rwlock_trywrlock)},/* PJT_RWLOCK_TRYWRLOCK */
257 	{DUAL_ENTRY(_pthread_rwlock_unlock)},	/* PJT_RWLOCK_UNLOCK */
258 	{DUAL_ENTRY(_pthread_rwlock_wrlock)},	/* PJT_RWLOCK_WRLOCK */
259 	{DUAL_ENTRY(_pthread_self)},		/* PJT_SELF */
260 	{DUAL_ENTRY(_pthread_setcancelstate)},	/* PJT_SETCANCELSTATE */
261 	{DUAL_ENTRY(_pthread_setcanceltype)},	/* PJT_SETCANCELTYPE */
262 	{DUAL_ENTRY(_pthread_setspecific)},	/* PJT_SETSPECIFIC */
263 	{DUAL_ENTRY(_pthread_sigmask)},		/* PJT_SIGMASK */
264 	{DUAL_ENTRY(_pthread_testcancel)},	/* PJT_TESTCANCEL */
265 	{DUAL_ENTRY(__pthread_cleanup_pop_imp)},/* PJT_CLEANUP_POP_IMP */
266 	{DUAL_ENTRY(__pthread_cleanup_push_imp)},/* PJT_CLEANUP_PUSH_IMP */
267 	{DUAL_ENTRY(_pthread_cancel_enter)},	/* PJT_CANCEL_ENTER */
268 	{DUAL_ENTRY(_pthread_cancel_leave)}		/* PJT_CANCEL_LEAVE */
269 };
270 
271 static int init_once = 0;
272 
273 /*
274  * For the shared version of the threads library, the above is sufficient.
275  * But for the archive version of the library, we need a little bit more.
276  * Namely, we must arrange for this particular module to be pulled in from
277  * the archive library at link time.  To accomplish that, we define and
278  * initialize a variable, "_thread_autoinit_dummy_decl".  This variable is
279  * referenced (as an extern) from libc/stdlib/exit.c. This will always
280  * create a need for this module, ensuring that it is present in the
281  * executable.
282  */
283 extern int _thread_autoinit_dummy_decl;
284 int _thread_autoinit_dummy_decl = 0;
285 
286 void
287 _thread_init_hack(void)
288 {
289 
290 	_libpthread_init(NULL);
291 }
292 
293 
294 /*
295  * Threaded process initialization.
296  *
297  * This is only called under two conditions:
298  *
299  *   1) Some thread routines have detected that the library hasn't yet
300  *      been initialized (_thr_initial == NULL && curthread == NULL), or
301  *
302  *   2) An explicit call to reinitialize after a fork (indicated
303  *      by curthread != NULL)
304  */
305 void
306 _libpthread_init(struct pthread *curthread)
307 {
308 	int first, dlopened;
309 
310 	/* Check if this function has already been called: */
311 	if ((_thr_initial != NULL) && (curthread == NULL))
312 		/* Only initialize the threaded application once. */
313 		return;
314 
315 	/*
316 	 * Check the size of the jump table to make sure it is preset
317 	 * with the correct number of entries.
318 	 */
319 	if (sizeof(jmp_table) != (sizeof(pthread_func_t) * PJT_MAX * 2))
320 		PANIC("Thread jump table not properly initialized");
321 	memcpy(__thr_jtable, jmp_table, sizeof(jmp_table));
322 	__thr_interpose_libc();
323 
324 	/* Initialize pthread private data. */
325 	init_private();
326 
327 	/* Set the initial thread. */
328 	if (curthread == NULL) {
329 		first = 1;
330 		/* Create and initialize the initial thread. */
331 		curthread = _thr_alloc(NULL);
332 		if (curthread == NULL)
333 			PANIC("Can't allocate initial thread");
334 		init_main_thread(curthread);
335 	} else {
336 		first = 0;
337 	}
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 		_thr_initial = curthread;
350 		dlopened = _rtld_is_dlopened(&_thread_autoinit_dummy_decl) != 0;
351 		_thr_signal_init(dlopened);
352 		if (_thread_event_mask & TD_CREATE)
353 			_thr_report_creation(curthread, curthread);
354 		/*
355 		 * Always use our rtld lock implementation.
356 		 * It is faster because it postpones signal handlers
357 		 * instead of calling sigprocmask(2).
358 		 */
359 		_thr_rtld_init();
360 	}
361 }
362 
363 /*
364  * This function and pthread_create() do a lot of the same things.
365  * It'd be nice to consolidate the common stuff in one place.
366  */
367 static void
368 init_main_thread(struct pthread *thread)
369 {
370 	struct sched_param sched_param;
371 	int i;
372 
373 	/* Setup the thread attributes. */
374 	thr_self(&thread->tid);
375 	thread->attr = _pthread_attr_default;
376 	/*
377 	 * Set up the thread stack.
378 	 *
379 	 * Create a red zone below the main stack.  All other stacks
380 	 * are constrained to a maximum size by the parameters
381 	 * passed to mmap(), but this stack is only limited by
382 	 * resource limits, so this stack needs an explicitly mapped
383 	 * red zone to protect the thread stack that is just beyond.
384 	 */
385 	if (mmap(_usrstack - _thr_stack_initial -
386 	    _thr_guard_default, _thr_guard_default, 0, MAP_ANON,
387 	    -1, 0) == MAP_FAILED)
388 		PANIC("Cannot allocate red zone for initial thread");
389 
390 	/*
391 	 * Mark the stack as an application supplied stack so that it
392 	 * isn't deallocated.
393 	 *
394 	 * XXX - I'm not sure it would hurt anything to deallocate
395 	 *       the main thread stack because deallocation doesn't
396 	 *       actually free() it; it just puts it in the free
397 	 *       stack queue for later reuse.
398 	 */
399 	thread->attr.stackaddr_attr = _usrstack - _thr_stack_initial;
400 	thread->attr.stacksize_attr = _thr_stack_initial;
401 	thread->attr.guardsize_attr = _thr_guard_default;
402 	thread->attr.flags |= THR_STACK_USER;
403 
404 	/*
405 	 * Write a magic value to the thread structure
406 	 * to help identify valid ones:
407 	 */
408 	thread->magic = THR_MAGIC;
409 
410 	thread->cancel_enable = 1;
411 	thread->cancel_async = 0;
412 
413 	/* Initialize the mutex queues */
414 	for (i = 0; i < TMQ_NITEMS; i++)
415 		TAILQ_INIT(&thread->mq[i]);
416 
417 	thread->state = PS_RUNNING;
418 
419 	_thr_getscheduler(thread->tid, &thread->attr.sched_policy,
420 		 &sched_param);
421 	thread->attr.prio = sched_param.sched_priority;
422 
423 #ifdef _PTHREAD_FORCED_UNWIND
424 	thread->unwind_stackend = _usrstack;
425 #endif
426 
427 	/* Others cleared to zero by thr_alloc() */
428 }
429 
430 static void
431 init_private(void)
432 {
433 	struct rlimit rlim;
434 	size_t len;
435 	int mib[2];
436 	char *env, *env_bigstack, *env_splitstack;
437 
438 	_thr_umutex_init(&_mutex_static_lock);
439 	_thr_umutex_init(&_cond_static_lock);
440 	_thr_umutex_init(&_rwlock_static_lock);
441 	_thr_umutex_init(&_keytable_lock);
442 	_thr_urwlock_init(&_thr_atfork_lock);
443 	_thr_umutex_init(&_thr_event_lock);
444 	_thr_umutex_init(&_suspend_all_lock);
445 	_thr_once_init();
446 	_thr_spinlock_init();
447 	_thr_list_init();
448 	_thr_wake_addr_init();
449 	_sleepq_init();
450 	_single_thread = NULL;
451 	_suspend_all_waiters = 0;
452 
453 	/*
454 	 * Avoid reinitializing some things if they don't need to be,
455 	 * e.g. after a fork().
456 	 */
457 	if (init_once == 0) {
458 		__thr_pshared_init();
459 		/* Find the stack top */
460 		mib[0] = CTL_KERN;
461 		mib[1] = KERN_USRSTACK;
462 		len = sizeof (_usrstack);
463 		if (sysctl(mib, 2, &_usrstack, &len, NULL, 0) == -1)
464 			PANIC("Cannot get kern.usrstack from sysctl");
465 		env_bigstack = getenv("LIBPTHREAD_BIGSTACK_MAIN");
466 		env_splitstack = getenv("LIBPTHREAD_SPLITSTACK_MAIN");
467 		if (env_bigstack != NULL || env_splitstack == NULL) {
468 			if (getrlimit(RLIMIT_STACK, &rlim) == -1)
469 				PANIC("Cannot get stack rlimit");
470 			_thr_stack_initial = rlim.rlim_cur;
471 		}
472 		len = sizeof(_thr_is_smp);
473 		sysctlbyname("kern.smp.cpus", &_thr_is_smp, &len, NULL, 0);
474 		_thr_is_smp = (_thr_is_smp > 1);
475 		_thr_page_size = getpagesize();
476 		_thr_guard_default = _thr_page_size;
477 		_pthread_attr_default.guardsize_attr = _thr_guard_default;
478 		_pthread_attr_default.stacksize_attr = _thr_stack_default;
479 		env = getenv("LIBPTHREAD_SPINLOOPS");
480 		if (env)
481 			_thr_spinloops = atoi(env);
482 		env = getenv("LIBPTHREAD_YIELDLOOPS");
483 		if (env)
484 			_thr_yieldloops = atoi(env);
485 		env = getenv("LIBPTHREAD_QUEUE_FIFO");
486 		if (env)
487 			_thr_queuefifo = atoi(env);
488 		TAILQ_INIT(&_thr_atfork_list);
489 	}
490 	init_once = 1;
491 }
492