lib/libthread_xu/thread/thr_fork.c

   1 /*
   2  * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
   3  * Copyright (c) 2003 Daniel Eischen <deischen@freebsd.org>
   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. Neither the name of the author nor the names of any co-contributors
  12  *    may be used to endorse or promote products derived from this software
  13  *    without specific prior written permission.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  *
  27  * $FreeBSD: src/lib/libpthread/thread/thr_atfork.c,v 1.1 2003/11/05 03:42:10 davidxu Exp $
  28  */
  29
  30 /*
  31  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  32  * All rights reserved.
  33  *
  34  * Redistribution and use in source and binary forms, with or without
  35  * modification, are permitted provided that the following conditions
  36  * are met:
  37  * 1. Redistributions of source code must retain the above copyright
  38  *    notice, this list of conditions and the following disclaimer.
  39  * 2. Redistributions in binary form must reproduce the above copyright
  40  *    notice, this list of conditions and the following disclaimer in the
  41  *    documentation and/or other materials provided with the distribution.
  42  * 3. All advertising materials mentioning features or use of this software
  43  *    must display the following acknowledgement:
  44  *      This product includes software developed by John Birrell.
  45  * 4. Neither the name of the author nor the names of any co-contributors
  46  *    may be used to endorse or promote products derived from this software
  47  *    without specific prior written permission.
  48  *
  49  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  50  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  51  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  52  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  53  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  54  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  55  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  56  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  57  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  58  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  59  * SUCH DAMAGE.
  60  *
  61  * $FreeBSD: src/lib/libpthread/thread/thr_fork.c,v 1.34 2003/11/05 18:18:45 deischen Exp $
  62  * $DragonFly: src/lib/libthread_xu/thread/thr_fork.c,v 1.6 2006/04/06 13:03:09 davidxu Exp $
  63  */
  64
  65 #include "namespace.h"
  66 #include <machine/tls.h>
  67
  68 #include <errno.h>
  69 #include <string.h>
  70 #include <stdlib.h>
  71 #include <unistd.h>
  72 #include <fcntl.h>
  73 #include <pthread.h>
  74 #include <spinlock.h>
  75 #include "un-namespace.h"
  76
  77 #include "libc_private.h"
  78 #include "thr_private.h"
  79
  80 struct atfork_head      _thr_atfork_list;
  81 umtx_t  _thr_atfork_lock;
  82
  83 int
  84 _pthread_atfork(void (*prepare)(void), void (*parent)(void),
  85     void (*child)(void))
  86 {
  87         struct pthread *curthread;
  88         struct pthread_atfork *af;
  89
  90         _thr_check_init();
  91
  92         if ((af = malloc(sizeof(struct pthread_atfork))) == NULL)
  93                 return (ENOMEM);
  94
  95         curthread = tls_get_curthread();
  96         af->prepare = prepare;
  97         af->parent = parent;
  98         af->child = child;
  99         THR_UMTX_LOCK(curthread, &_thr_atfork_lock);
 100         TAILQ_INSERT_TAIL(&_thr_atfork_list, af, qe);
 101         THR_UMTX_UNLOCK(curthread, &_thr_atfork_lock);
 102         return (0);
 103 }
 104
 105 /*
 106  * For a while, allow libpthread to work with a libc that doesn't
 107  * export the malloc lock.
 108  */
 109 #pragma weak __malloc_lock
 110
 111 pid_t _fork(void);
 112
 113 pid_t
 114 _fork(void)
 115 {
 116         static umtx_t inprogress;
 117         static int waiters;
 118         umtx_t tmp;
 119
 120         struct pthread *curthread;
 121         struct pthread_atfork *af;
 122         pid_t ret;
 123         int errsave;
 124 #ifndef __DragonFly__
 125         int unlock_malloc;
 126 #endif
 127
 128         if (!_thr_is_inited())
 129                 return (__sys_fork());
 130
 131         curthread = tls_get_curthread();
 132
 133         THR_UMTX_LOCK(curthread, &_thr_atfork_lock);
 134         tmp = inprogress;
 135         while (tmp) {
 136                 waiters++;
 137                 THR_UMTX_UNLOCK(curthread, &_thr_atfork_lock);
 138                 _thr_umtx_wait(&inprogress, tmp, NULL, 0);
 139                 THR_UMTX_LOCK(curthread, &_thr_atfork_lock);
 140                 waiters--;
 141                 tmp = inprogress;
 142         }
 143         inprogress = 1;
 144         THR_UMTX_UNLOCK(curthread, &_thr_atfork_lock);
 145
 146         /* Run down atfork prepare handlers. */
 147         TAILQ_FOREACH_REVERSE(af, &_thr_atfork_list, atfork_head, qe) {
 148                 if (af->prepare != NULL)
 149                         af->prepare();
 150         }
 151
 152 #ifndef __DragonFly__
 153         /*
 154          * Try our best to protect memory from being corrupted in
 155          * child process because another thread in malloc code will
 156          * simply be kill by fork().
 157          */
 158         if ((_thr_isthreaded() != 0) && (__malloc_lock != NULL)) {
 159                 unlock_malloc = 1;
 160                 _spinlock(__malloc_lock);
 161         } else {
 162                 unlock_malloc = 0;
 163         }
 164 #endif
 165
 166         /*
 167          * Block all signals until we reach a safe point.
 168          */
 169         _thr_signal_block(curthread);
 170
 171         /* Fork a new process: */
 172         if ((ret = __sys_fork()) == 0) {
 173                 /* Child process */
 174                 errsave = errno;
 175                 inprogress = 0;
 176                 curthread->cancelflags &= ~THR_CANCEL_NEEDED;
 177                 /*
 178                  * Thread list will be reinitialized, and later we call
 179                  * _libpthread_init(), it will add us back to list.
 180                  */
 181                 curthread->tlflags &= ~(TLFLAGS_IN_TDLIST | TLFLAGS_DETACHED);
 182
 183                 /* child is a new kernel thread. */
 184                 curthread->tid = _thr_get_tid();
 185
 186                 /* clear other threads locked us. */
 187                 _thr_umtx_init(&curthread->lock);
 188                 _thr_umtx_init(&_thr_atfork_lock);
 189                 _thr_setthreaded(0);
 190
 191                 /* reinitialize libc spinlocks, this includes __malloc_lock. */
 192                 _thr_spinlock_init();
 193                 _mutex_fork(curthread);
 194
 195                 /* reinitalize library. */
 196                 _libpthread_init(curthread);
 197
 198                 /* Ready to continue, unblock signals. */
 199                 _thr_signal_unblock(curthread);
 200
 201                 /* Run down atfork child handlers. */
 202                 TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
 203                         if (af->child != NULL)
 204                                 af->child();
 205                 }
 206         } else {
 207                 /* Parent process */
 208                 errsave = errno;
 209
 210 #ifndef __DragonFly__
 211                 if (unlock_malloc)
 212                         _spinunlock(__malloc_lock);
 213 #endif
 214
 215                 /* Ready to continue, unblock signals. */
 216                 _thr_signal_unblock(curthread);
 217
 218                 /* Run down atfork parent handlers. */
 219                 TAILQ_FOREACH(af, &_thr_atfork_list, qe) {
 220                         if (af->parent != NULL)
 221                                 af->parent();
 222                 }
 223
 224                 THR_UMTX_LOCK(curthread, &_thr_atfork_lock);
 225                 inprogress = 0;
 226                 if (waiters)
 227                         _thr_umtx_wake(&inprogress, waiters);
 228                 THR_UMTX_UNLOCK(curthread, &_thr_atfork_lock);
 229         }
 230         errno = errsave;
 231
 232         /* Return the process ID: */
 233         return (ret);
 234 }
 235
 236 __strong_reference(_fork, fork);
 237 __strong_reference(_pthread_atfork, pthread_atfork);
 238