lib/libthr/thread/thr_init.c

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