lib/libc_r/uthread/uthread_fork.c

   1 /*
   2  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the author nor the names of any co-contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * $FreeBSD$
  30  */
  31 #include <sys/param.h>
  32 #include <errno.h>
  33 #include <string.h>
  34 #include <stdlib.h>
  35 #include <unistd.h>
  36 #include <fcntl.h>
  37 #include <pthread.h>
  38 #include "pthread_private.h"
  39
  40 static void     free_thread_resources(struct pthread *thread);
  41
  42 __weak_reference(_fork, fork);
  43
  44 pid_t
  45 _fork(void)
  46 {
  47         struct pthread  *curthread = _get_curthread();
  48         struct pthread_atfork *af;
  49         int             i, flags, use_deadlist = 0;
  50         pid_t           ret;
  51         pthread_t       pthread;
  52         pthread_t       pthread_save;
  53
  54         /*
  55          * Defer signals to protect the scheduling queues from access
  56          * by the signal handler:
  57          */
  58         _thread_kern_sig_defer();
  59
  60         _pthread_mutex_lock(&_atfork_mutex);
  61
  62         /* Run down atfork prepare handlers. */
  63         TAILQ_FOREACH_REVERSE(af, &_atfork_list, atfork_head, qe) {
  64                 if (af->prepare != NULL)
  65                         af->prepare();
  66         }
  67
  68         /* Fork a new process: */
  69         if ((ret = __sys_fork()) != 0) {
  70                 /* Run down atfork parent handlers. */
  71                 TAILQ_FOREACH(af, &_atfork_list, qe) {
  72                         if (af->parent != NULL)
  73                         af->parent();
  74                 }
  75                 _pthread_mutex_unlock(&_atfork_mutex);
  76
  77         } else {
  78                 /* Close the pthread kernel pipe: */
  79                 __sys_close(_thread_kern_pipe[0]);
  80                 __sys_close(_thread_kern_pipe[1]);
  81
  82                 /* Reset signals pending for the running thread: */
  83                 sigemptyset(&curthread->sigpend);
  84
  85                 /*
  86                  * Create a pipe that is written to by the signal handler to
  87                  * prevent signals being missed in calls to
  88                  * __sys_select:
  89                  */
  90                 if (__sys_pipe(_thread_kern_pipe) != 0) {
  91                         /* Cannot create pipe, so abort: */
  92                         PANIC("Cannot create pthread kernel pipe for forked process");
  93                 }
  94                 /* Get the flags for the read pipe: */
  95                 else if ((flags = __sys_fcntl(_thread_kern_pipe[0], F_GETFL, NULL)) == -1) {
  96                         /* Abort this application: */
  97                         abort();
  98                 }
  99                 /* Make the read pipe non-blocking: */
 100                 else if (__sys_fcntl(_thread_kern_pipe[0], F_SETFL, flags | O_NONBLOCK) == -1) {
 101                         /* Abort this application: */
 102                         abort();
 103                 }
 104                 /* Get the flags for the write pipe: */
 105                 else if ((flags = __sys_fcntl(_thread_kern_pipe[1], F_GETFL, NULL)) == -1) {
 106                         /* Abort this application: */
 107                         abort();
 108                 }
 109                 /* Make the write pipe non-blocking: */
 110                 else if (__sys_fcntl(_thread_kern_pipe[1], F_SETFL, flags | O_NONBLOCK) == -1) {
 111                         /* Abort this application: */
 112                         abort();
 113                 }
 114                 /* Reinitialize the GC mutex: */
 115                 else if (_mutex_reinit(&_gc_mutex) != 0) {
 116                         /* Abort this application: */
 117                         PANIC("Cannot initialize GC mutex for forked process");
 118                 }
 119                 /* Reinitialize the GC condition variable: */
 120                 else if (_cond_reinit(&_gc_cond) != 0) {
 121                         /* Abort this application: */
 122                         PANIC("Cannot initialize GC condvar for forked process");
 123                 }
 124                 /* Initialize the ready queue: */
 125                 else if (_pq_init(&_readyq) != 0) {
 126                         /* Abort this application: */
 127                         PANIC("Cannot initialize priority ready queue.");
 128                 } else {
 129                         /*
 130                          * Enter a loop to remove all threads other than
 131                          * the running thread from the thread list:
 132                          */
 133                         if ((pthread = TAILQ_FIRST(&_thread_list)) == NULL) {
 134                                 pthread = TAILQ_FIRST(&_dead_list);
 135                                 use_deadlist = 1;
 136                         }
 137                         while (pthread != NULL) {
 138                                 /* Save the thread to be freed: */
 139                                 pthread_save = pthread;
 140
 141                                 /*
 142                                  * Advance to the next thread before
 143                                  * destroying the current thread:
 144                                  */
 145                                 if (use_deadlist != 0)
 146                                         pthread = TAILQ_NEXT(pthread, dle);
 147                                 else
 148                                         pthread = TAILQ_NEXT(pthread, tle);
 149
 150                                 /* Make sure this isn't the running thread: */
 151                                 if (pthread_save != curthread) {
 152                                         /*
 153                                          * Remove this thread from the
 154                                          * appropriate list:
 155                                          */
 156                                         if (use_deadlist != 0)
 157                                                 TAILQ_REMOVE(&_thread_list,
 158                                                     pthread_save, dle);
 159                                         else
 160                                                 TAILQ_REMOVE(&_thread_list,
 161                                                     pthread_save, tle);
 162
 163                                         free_thread_resources(pthread_save);
 164                                 }
 165
 166                                 /*
 167                                  * Switch to the deadlist when the active
 168                                  * thread list has been consumed.  This can't
 169                                  * be at the top of the loop because it is
 170                                  * used to determine to which list the thread
 171                                  * belongs (when it is removed from the list).
 172                                  */
 173                                 if (pthread == NULL) {
 174                                         pthread = TAILQ_FIRST(&_dead_list);
 175                                         use_deadlist = 1;
 176                                 }
 177                         }
 178
 179                         /* Treat the current thread as the initial thread: */
 180                         _thread_initial = curthread;
 181
 182                         /* Re-init the dead thread list: */
 183                         TAILQ_INIT(&_dead_list);
 184
 185                         /* Re-init the waiting and work queues. */
 186                         TAILQ_INIT(&_waitingq);
 187                         TAILQ_INIT(&_workq);
 188
 189                         /* Re-init the threads mutex queue: */
 190                         TAILQ_INIT(&curthread->mutexq);
 191
 192                         /* No spinlocks yet: */
 193                         _spinblock_count = 0;
 194
 195                         /* Don't queue signals yet: */
 196                         _queue_signals = 0;
 197
 198                         /* Initialize the scheduling switch hook routine: */
 199                         _sched_switch_hook = NULL;
 200
 201                         /* Clear out any locks in the file descriptor table: */
 202                         for (i = 0; i < _thread_dtablesize; i++) {
 203                                 if (_thread_fd_table[i] != NULL) {
 204                                         /* Initialise the file locks: */
 205                                         memset(&_thread_fd_table[i]->lock, 0,
 206                                             sizeof(_thread_fd_table[i]->lock));
 207                                         _thread_fd_table[i]->r_owner = NULL;
 208                                         _thread_fd_table[i]->w_owner = NULL;
 209                                         _thread_fd_table[i]->r_fname = NULL;
 210                                         _thread_fd_table[i]->w_fname = NULL;
 211                                         _thread_fd_table[i]->r_lineno = 0;;
 212                                         _thread_fd_table[i]->w_lineno = 0;;
 213                                         _thread_fd_table[i]->r_lockcount = 0;;
 214                                         _thread_fd_table[i]->w_lockcount = 0;;
 215
 216                                         /* Initialise the read/write queues: */
 217                                         TAILQ_INIT(&_thread_fd_table[i]->r_queue);
 218                                         TAILQ_INIT(&_thread_fd_table[i]->w_queue);
 219                                 }
 220                         }
 221                 }
 222                 /* Run down atfork child handlers. */
 223                 TAILQ_FOREACH(af, &_atfork_list, qe) {
 224                         if (af->child != NULL)
 225                                 af->child();
 226                 }
 227                 _mutex_reinit(&_atfork_mutex);
 228         }
 229
 230
 231         /*
 232          * Undefer and handle pending signals, yielding if necessary:
 233          */
 234         _thread_kern_sig_undefer();
 235
 236         /* Return the process ID: */
 237         return (ret);
 238 }
 239
 240 static void
 241 free_thread_resources(struct pthread *thread)
 242 {
 243
 244         /* Check to see if the threads library allocated the stack. */
 245         if ((thread->attr.stackaddr_attr == NULL) && (thread->stack != NULL)) {
 246                 /*
 247                  * Since this is being called from fork, we are currently single
 248                  * threaded so there is no need to protect the call to
 249                  * _thread_stack_free() with _gc_mutex.
 250                  */
 251                 _thread_stack_free(thread->stack, thread->attr.stacksize_attr,
 252                     thread->attr.guardsize_attr);
 253         }
 254
 255         if (thread->specific != NULL)
 256                 free(thread->specific);
 257
 258         if (thread->poll_data.fds != NULL)
 259                 free(thread->poll_data.fds);
 260
 261         free(thread);
 262 }