xref: /freebsd/lib/libthr/thread/thr_init.c (revision 937a2000893c36b8f9ba7898a1afc66a9f20db16)
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 urwlock	_thr_atfork_lock = DEFAULT_URWLOCK;
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  };
94  
95  struct pthread_mutex_attr _pthread_mutexattr_adaptive_default = {
96  	.m_type = PTHREAD_MUTEX_ADAPTIVE_NP,
97  	.m_protocol = PTHREAD_PRIO_NONE,
98  	.m_ceiling = 0
99  };
100  
101  /* Default condition variable attributes: */
102  struct pthread_cond_attr _pthread_condattr_default = {
103  	.c_pshared = PTHREAD_PROCESS_PRIVATE,
104  	.c_clockid = CLOCK_REALTIME
105  };
106  
107  pid_t		_thr_pid;
108  int		_thr_is_smp = 0;
109  size_t		_thr_guard_default;
110  size_t		_thr_stack_default = THR_STACK_DEFAULT;
111  size_t		_thr_stack_initial = THR_STACK_INITIAL;
112  int		_thr_page_size;
113  int		_thr_spinloops;
114  int		_thr_yieldloops;
115  int		_thr_queuefifo = 4;
116  int		_gc_count;
117  struct umutex	_mutex_static_lock = DEFAULT_UMUTEX;
118  struct umutex	_cond_static_lock = DEFAULT_UMUTEX;
119  struct umutex	_rwlock_static_lock = DEFAULT_UMUTEX;
120  struct umutex	_keytable_lock = DEFAULT_UMUTEX;
121  struct urwlock	_thr_list_lock = DEFAULT_URWLOCK;
122  struct umutex	_thr_event_lock = DEFAULT_UMUTEX;
123  struct umutex	_suspend_all_lock = DEFAULT_UMUTEX;
124  struct pthread	*_single_thread;
125  int		_suspend_all_cycle;
126  int		_suspend_all_waiters;
127  
128  int	__pthread_cond_wait(pthread_cond_t *, pthread_mutex_t *);
129  int	__pthread_mutex_lock(pthread_mutex_t *);
130  int	__pthread_mutex_trylock(pthread_mutex_t *);
131  void	_thread_init_hack(void) __attribute__ ((constructor));
132  
133  static void init_private(void);
134  static void init_main_thread(struct pthread *thread);
135  
136  /*
137   * All weak references used within libc should be in this table.
138   * This is so that static libraries will work.
139   */
140  
141  STATIC_LIB_REQUIRE(_fork);
142  STATIC_LIB_REQUIRE(_pthread_getspecific);
143  STATIC_LIB_REQUIRE(_pthread_key_create);
144  STATIC_LIB_REQUIRE(_pthread_key_delete);
145  STATIC_LIB_REQUIRE(_pthread_mutex_destroy);
146  STATIC_LIB_REQUIRE(_pthread_mutex_init);
147  STATIC_LIB_REQUIRE(_pthread_mutex_lock);
148  STATIC_LIB_REQUIRE(_pthread_mutex_trylock);
149  STATIC_LIB_REQUIRE(_pthread_mutex_unlock);
150  STATIC_LIB_REQUIRE(_pthread_mutexattr_init);
151  STATIC_LIB_REQUIRE(_pthread_mutexattr_destroy);
152  STATIC_LIB_REQUIRE(_pthread_mutexattr_settype);
153  STATIC_LIB_REQUIRE(_pthread_once);
154  STATIC_LIB_REQUIRE(_pthread_setspecific);
155  STATIC_LIB_REQUIRE(_raise);
156  STATIC_LIB_REQUIRE(_sem_destroy);
157  STATIC_LIB_REQUIRE(_sem_getvalue);
158  STATIC_LIB_REQUIRE(_sem_init);
159  STATIC_LIB_REQUIRE(_sem_post);
160  STATIC_LIB_REQUIRE(_sem_timedwait);
161  STATIC_LIB_REQUIRE(_sem_trywait);
162  STATIC_LIB_REQUIRE(_sem_wait);
163  STATIC_LIB_REQUIRE(_sigaction);
164  STATIC_LIB_REQUIRE(_sigprocmask);
165  STATIC_LIB_REQUIRE(_sigsuspend);
166  STATIC_LIB_REQUIRE(_sigtimedwait);
167  STATIC_LIB_REQUIRE(_sigwait);
168  STATIC_LIB_REQUIRE(_sigwaitinfo);
169  STATIC_LIB_REQUIRE(_spinlock);
170  STATIC_LIB_REQUIRE(_spinlock_debug);
171  STATIC_LIB_REQUIRE(_spinunlock);
172  STATIC_LIB_REQUIRE(_thread_init_hack);
173  
174  /*
175   * These are needed when linking statically.  All references within
176   * libgcc (and in the future libc) to these routines are weak, but
177   * if they are not (strongly) referenced by the application or other
178   * libraries, then the actual functions will not be loaded.
179   */
180  STATIC_LIB_REQUIRE(_pthread_once);
181  STATIC_LIB_REQUIRE(_pthread_key_create);
182  STATIC_LIB_REQUIRE(_pthread_key_delete);
183  STATIC_LIB_REQUIRE(_pthread_getspecific);
184  STATIC_LIB_REQUIRE(_pthread_setspecific);
185  STATIC_LIB_REQUIRE(_pthread_mutex_init);
186  STATIC_LIB_REQUIRE(_pthread_mutex_destroy);
187  STATIC_LIB_REQUIRE(_pthread_mutex_lock);
188  STATIC_LIB_REQUIRE(_pthread_mutex_trylock);
189  STATIC_LIB_REQUIRE(_pthread_mutex_unlock);
190  STATIC_LIB_REQUIRE(_pthread_create);
191  
192  /* Pull in all symbols required by libthread_db */
193  STATIC_LIB_REQUIRE(_thread_state_running);
194  
195  #define	DUAL_ENTRY(entry)	\
196  	(pthread_func_t)entry, (pthread_func_t)entry
197  
198  static pthread_func_t jmp_table[][2] = {
199  	{DUAL_ENTRY(_pthread_atfork)},	/* PJT_ATFORK */
200  	{DUAL_ENTRY(_pthread_attr_destroy)},	/* PJT_ATTR_DESTROY */
201  	{DUAL_ENTRY(_pthread_attr_getdetachstate)},	/* PJT_ATTR_GETDETACHSTATE */
202  	{DUAL_ENTRY(_pthread_attr_getguardsize)},	/* PJT_ATTR_GETGUARDSIZE */
203  	{DUAL_ENTRY(_pthread_attr_getinheritsched)},	/* PJT_ATTR_GETINHERITSCHED */
204  	{DUAL_ENTRY(_pthread_attr_getschedparam)},	/* PJT_ATTR_GETSCHEDPARAM */
205  	{DUAL_ENTRY(_pthread_attr_getschedpolicy)},	/* PJT_ATTR_GETSCHEDPOLICY */
206  	{DUAL_ENTRY(_pthread_attr_getscope)},	/* PJT_ATTR_GETSCOPE */
207  	{DUAL_ENTRY(_pthread_attr_getstackaddr)},	/* PJT_ATTR_GETSTACKADDR */
208  	{DUAL_ENTRY(_pthread_attr_getstacksize)},	/* PJT_ATTR_GETSTACKSIZE */
209  	{DUAL_ENTRY(_pthread_attr_init)},	/* PJT_ATTR_INIT */
210  	{DUAL_ENTRY(_pthread_attr_setdetachstate)},	/* PJT_ATTR_SETDETACHSTATE */
211  	{DUAL_ENTRY(_pthread_attr_setguardsize)},	/* PJT_ATTR_SETGUARDSIZE */
212  	{DUAL_ENTRY(_pthread_attr_setinheritsched)},	/* PJT_ATTR_SETINHERITSCHED */
213  	{DUAL_ENTRY(_pthread_attr_setschedparam)},	/* PJT_ATTR_SETSCHEDPARAM */
214  	{DUAL_ENTRY(_pthread_attr_setschedpolicy)},	/* PJT_ATTR_SETSCHEDPOLICY */
215  	{DUAL_ENTRY(_pthread_attr_setscope)},	/* PJT_ATTR_SETSCOPE */
216  	{DUAL_ENTRY(_pthread_attr_setstackaddr)},	/* PJT_ATTR_SETSTACKADDR */
217  	{DUAL_ENTRY(_pthread_attr_setstacksize)},	/* PJT_ATTR_SETSTACKSIZE */
218  	{DUAL_ENTRY(_pthread_cancel)},	/* PJT_CANCEL */
219  	{DUAL_ENTRY(_pthread_cleanup_pop)},	/* PJT_CLEANUP_POP */
220  	{DUAL_ENTRY(_pthread_cleanup_push)},	/* PJT_CLEANUP_PUSH */
221  	{DUAL_ENTRY(_pthread_cond_broadcast)},	/* PJT_COND_BROADCAST */
222  	{DUAL_ENTRY(_pthread_cond_destroy)},	/* PJT_COND_DESTROY */
223  	{DUAL_ENTRY(_pthread_cond_init)},	/* PJT_COND_INIT */
224  	{DUAL_ENTRY(_pthread_cond_signal)},	/* PJT_COND_SIGNAL */
225  	{DUAL_ENTRY(_pthread_cond_timedwait)},	/* PJT_COND_TIMEDWAIT */
226  	{(pthread_func_t)__pthread_cond_wait,
227  	 (pthread_func_t)_pthread_cond_wait},	/* PJT_COND_WAIT */
228  	{DUAL_ENTRY(_pthread_detach)},	/* PJT_DETACH */
229  	{DUAL_ENTRY(_pthread_equal)},	/* PJT_EQUAL */
230  	{DUAL_ENTRY(_pthread_exit)},	/* PJT_EXIT */
231  	{DUAL_ENTRY(_pthread_getspecific)},	/* PJT_GETSPECIFIC */
232  	{DUAL_ENTRY(_pthread_join)},	/* PJT_JOIN */
233  	{DUAL_ENTRY(_pthread_key_create)},	/* PJT_KEY_CREATE */
234  	{DUAL_ENTRY(_pthread_key_delete)},	/* PJT_KEY_DELETE*/
235  	{DUAL_ENTRY(_pthread_kill)},	/* PJT_KILL */
236  	{DUAL_ENTRY(_pthread_main_np)},		/* PJT_MAIN_NP */
237  	{DUAL_ENTRY(_pthread_mutexattr_destroy)}, /* PJT_MUTEXATTR_DESTROY */
238  	{DUAL_ENTRY(_pthread_mutexattr_init)},	/* PJT_MUTEXATTR_INIT */
239  	{DUAL_ENTRY(_pthread_mutexattr_settype)}, /* PJT_MUTEXATTR_SETTYPE */
240  	{DUAL_ENTRY(_pthread_mutex_destroy)},	/* PJT_MUTEX_DESTROY */
241  	{DUAL_ENTRY(_pthread_mutex_init)},	/* PJT_MUTEX_INIT */
242  	{(pthread_func_t)__pthread_mutex_lock,
243  	 (pthread_func_t)_pthread_mutex_lock},	/* PJT_MUTEX_LOCK */
244  	{(pthread_func_t)__pthread_mutex_trylock,
245  	 (pthread_func_t)_pthread_mutex_trylock},/* PJT_MUTEX_TRYLOCK */
246  	{DUAL_ENTRY(_pthread_mutex_unlock)},	/* PJT_MUTEX_UNLOCK */
247  	{DUAL_ENTRY(_pthread_once)},		/* PJT_ONCE */
248  	{DUAL_ENTRY(_pthread_rwlock_destroy)},	/* PJT_RWLOCK_DESTROY */
249  	{DUAL_ENTRY(_pthread_rwlock_init)},	/* PJT_RWLOCK_INIT */
250  	{DUAL_ENTRY(_pthread_rwlock_rdlock)},	/* PJT_RWLOCK_RDLOCK */
251  	{DUAL_ENTRY(_pthread_rwlock_tryrdlock)},/* PJT_RWLOCK_TRYRDLOCK */
252  	{DUAL_ENTRY(_pthread_rwlock_trywrlock)},/* PJT_RWLOCK_TRYWRLOCK */
253  	{DUAL_ENTRY(_pthread_rwlock_unlock)},	/* PJT_RWLOCK_UNLOCK */
254  	{DUAL_ENTRY(_pthread_rwlock_wrlock)},	/* PJT_RWLOCK_WRLOCK */
255  	{DUAL_ENTRY(_pthread_self)},		/* PJT_SELF */
256  	{DUAL_ENTRY(_pthread_setcancelstate)},	/* PJT_SETCANCELSTATE */
257  	{DUAL_ENTRY(_pthread_setcanceltype)},	/* PJT_SETCANCELTYPE */
258  	{DUAL_ENTRY(_pthread_setspecific)},	/* PJT_SETSPECIFIC */
259  	{DUAL_ENTRY(_pthread_sigmask)},		/* PJT_SIGMASK */
260  	{DUAL_ENTRY(_pthread_testcancel)},	/* PJT_TESTCANCEL */
261  	{DUAL_ENTRY(__pthread_cleanup_pop_imp)},/* PJT_CLEANUP_POP_IMP */
262  	{DUAL_ENTRY(__pthread_cleanup_push_imp)},/* PJT_CLEANUP_PUSH_IMP */
263  	{DUAL_ENTRY(_pthread_cancel_enter)},	/* PJT_CANCEL_ENTER */
264  	{DUAL_ENTRY(_pthread_cancel_leave)}		/* PJT_CANCEL_LEAVE */
265  };
266  
267  static int init_once = 0;
268  
269  /*
270   * For the shared version of the threads library, the above is sufficient.
271   * But for the archive version of the library, we need a little bit more.
272   * Namely, we must arrange for this particular module to be pulled in from
273   * the archive library at link time.  To accomplish that, we define and
274   * initialize a variable, "_thread_autoinit_dummy_decl".  This variable is
275   * referenced (as an extern) from libc/stdlib/exit.c. This will always
276   * create a need for this module, ensuring that it is present in the
277   * executable.
278   */
279  extern int _thread_autoinit_dummy_decl;
280  int _thread_autoinit_dummy_decl = 0;
281  
282  void
283  _thread_init_hack(void)
284  {
285  
286  	_libpthread_init(NULL);
287  }
288  
289  
290  /*
291   * Threaded process initialization.
292   *
293   * This is only called under two conditions:
294   *
295   *   1) Some thread routines have detected that the library hasn't yet
296   *      been initialized (_thr_initial == NULL && curthread == NULL), or
297   *
298   *   2) An explicit call to reinitialize after a fork (indicated
299   *      by curthread != NULL)
300   */
301  void
302  _libpthread_init(struct pthread *curthread)
303  {
304  	int fd, first = 0;
305  
306  	/* Check if this function has already been called: */
307  	if ((_thr_initial != NULL) && (curthread == NULL))
308  		/* Only initialize the threaded application once. */
309  		return;
310  
311  	/*
312  	 * Check the size of the jump table to make sure it is preset
313  	 * with the correct number of entries.
314  	 */
315  	if (sizeof(jmp_table) != (sizeof(pthread_func_t) * PJT_MAX * 2))
316  		PANIC("Thread jump table not properly initialized");
317  	memcpy(__thr_jtable, jmp_table, sizeof(jmp_table));
318  
319  	/*
320  	 * Check for the special case of this process running as
321  	 * or in place of init as pid = 1:
322  	 */
323  	if ((_thr_pid = getpid()) == 1) {
324  		/*
325  		 * Setup a new session for this process which is
326  		 * assumed to be running as root.
327  		 */
328  		if (setsid() == -1)
329  			PANIC("Can't set session ID");
330  		if (revoke(_PATH_CONSOLE) != 0)
331  			PANIC("Can't revoke console");
332  		if ((fd = __sys_open(_PATH_CONSOLE, O_RDWR)) < 0)
333  			PANIC("Can't open console");
334  		if (setlogin("root") == -1)
335  			PANIC("Can't set login to root");
336  		if (_ioctl(fd, TIOCSCTTY, (char *) NULL) == -1)
337  			PANIC("Can't set controlling terminal");
338  	}
339  
340  	/* Initialize pthread private data. */
341  	init_private();
342  
343  	/* Set the initial thread. */
344  	if (curthread == NULL) {
345  		first = 1;
346  		/* Create and initialize the initial thread. */
347  		curthread = _thr_alloc(NULL);
348  		if (curthread == NULL)
349  			PANIC("Can't allocate initial thread");
350  		init_main_thread(curthread);
351  	}
352  	/*
353  	 * Add the thread to the thread list queue.
354  	 */
355  	THR_LIST_ADD(curthread);
356  	_thread_active_threads = 1;
357  
358  	/* Setup the thread specific data */
359  	_tcb_set(curthread->tcb);
360  
361  	if (first) {
362  		_thr_initial = curthread;
363  		_thr_signal_init();
364  		if (_thread_event_mask & TD_CREATE)
365  			_thr_report_creation(curthread, curthread);
366  		/*
367  		 * Always use our rtld lock implementation.
368  		 * It is faster because it postpones signal handlers
369  		 * instead of calling sigprocmask(2).
370  		 */
371  		_thr_rtld_init();
372  	}
373  }
374  
375  /*
376   * This function and pthread_create() do a lot of the same things.
377   * It'd be nice to consolidate the common stuff in one place.
378   */
379  static void
380  init_main_thread(struct pthread *thread)
381  {
382  	struct sched_param sched_param;
383  
384  	/* Setup the thread attributes. */
385  	thr_self(&thread->tid);
386  	thread->attr = _pthread_attr_default;
387  	/*
388  	 * Set up the thread stack.
389  	 *
390  	 * Create a red zone below the main stack.  All other stacks
391  	 * are constrained to a maximum size by the parameters
392  	 * passed to mmap(), but this stack is only limited by
393  	 * resource limits, so this stack needs an explicitly mapped
394  	 * red zone to protect the thread stack that is just beyond.
395  	 */
396  	if (mmap(_usrstack - _thr_stack_initial -
397  	    _thr_guard_default, _thr_guard_default, 0, MAP_ANON,
398  	    -1, 0) == MAP_FAILED)
399  		PANIC("Cannot allocate red zone for initial thread");
400  
401  	/*
402  	 * Mark the stack as an application supplied stack so that it
403  	 * isn't deallocated.
404  	 *
405  	 * XXX - I'm not sure it would hurt anything to deallocate
406  	 *       the main thread stack because deallocation doesn't
407  	 *       actually free() it; it just puts it in the free
408  	 *       stack queue for later reuse.
409  	 */
410  	thread->attr.stackaddr_attr = _usrstack - _thr_stack_initial;
411  	thread->attr.stacksize_attr = _thr_stack_initial;
412  	thread->attr.guardsize_attr = _thr_guard_default;
413  	thread->attr.flags |= THR_STACK_USER;
414  
415  	/*
416  	 * Write a magic value to the thread structure
417  	 * to help identify valid ones:
418  	 */
419  	thread->magic = THR_MAGIC;
420  
421  	thread->cancel_enable = 1;
422  	thread->cancel_async = 0;
423  
424  	/* Initialize the mutex queue: */
425  	TAILQ_INIT(&thread->mutexq);
426  	TAILQ_INIT(&thread->pp_mutexq);
427  
428  	thread->state = PS_RUNNING;
429  
430  	_thr_getscheduler(thread->tid, &thread->attr.sched_policy,
431  		 &sched_param);
432  	thread->attr.prio = sched_param.sched_priority;
433  
434  #ifdef _PTHREAD_FORCED_UNWIND
435  	thread->unwind_stackend = _usrstack;
436  #endif
437  
438  	/* Others cleared to zero by thr_alloc() */
439  }
440  
441  static void
442  init_private(void)
443  {
444  	size_t len;
445  	int mib[2];
446  	char *env;
447  
448  	_thr_umutex_init(&_mutex_static_lock);
449  	_thr_umutex_init(&_cond_static_lock);
450  	_thr_umutex_init(&_rwlock_static_lock);
451  	_thr_umutex_init(&_keytable_lock);
452  	_thr_urwlock_init(&_thr_atfork_lock);
453  	_thr_umutex_init(&_thr_event_lock);
454  	_thr_umutex_init(&_suspend_all_lock);
455  	_thr_once_init();
456  	_thr_spinlock_init();
457  	_thr_list_init();
458  	_thr_wake_addr_init();
459  	_sleepq_init();
460  	_single_thread = NULL;
461  	_suspend_all_waiters = 0;
462  
463  	/*
464  	 * Avoid reinitializing some things if they don't need to be,
465  	 * e.g. after a fork().
466  	 */
467  	if (init_once == 0) {
468  		/* Find the stack top */
469  		mib[0] = CTL_KERN;
470  		mib[1] = KERN_USRSTACK;
471  		len = sizeof (_usrstack);
472  		if (sysctl(mib, 2, &_usrstack, &len, NULL, 0) == -1)
473  			PANIC("Cannot get kern.usrstack from sysctl");
474  		len = sizeof(_thr_is_smp);
475  		sysctlbyname("kern.smp.cpus", &_thr_is_smp, &len, NULL, 0);
476  		_thr_is_smp = (_thr_is_smp > 1);
477  		_thr_page_size = getpagesize();
478  		_thr_guard_default = _thr_page_size;
479  		_pthread_attr_default.guardsize_attr = _thr_guard_default;
480  		_pthread_attr_default.stacksize_attr = _thr_stack_default;
481  		env = getenv("LIBPTHREAD_SPINLOOPS");
482  		if (env)
483  			_thr_spinloops = atoi(env);
484  		env = getenv("LIBPTHREAD_YIELDLOOPS");
485  		if (env)
486  			_thr_yieldloops = atoi(env);
487  		env = getenv("LIBPTHREAD_QUEUE_FIFO");
488  		if (env)
489  			_thr_queuefifo = atoi(env);
490  		TAILQ_INIT(&_thr_atfork_list);
491  	}
492  	init_once = 1;
493  }
494