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. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by John Birrell.
  16  * 4. Neither the name of the author nor the names of any co-contributors
  17  *    may be used to endorse or promote products derived from this software
  18  *    without specific prior written permission.
  19  *
  20  * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
  21  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  22  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  23  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  24  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  25  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  26  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  27  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  28  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  29  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  *
  32  * $FreeBSD$
  33  */
  34 #include <sys/param.h>
  35 #include <errno.h>
  36 #include <string.h>
  37 #include <stdlib.h>
  38 #include <unistd.h>
  39 #include <fcntl.h>
  40 #include <pthread.h>
  41 #include "pthread_private.h"
  42
  43 static void     free_thread_resources(struct pthread *thread);
  44
  45 __weak_reference(_fork, fork);
  46
  47 pid_t
  48 _fork(void)
  49 {
  50         struct pthread  *curthread = _get_curthread();
  51         struct pthread_atfork *af;
  52         int             i, flags, use_deadlist = 0;
  53         pid_t           ret;
  54         pthread_t       pthread;
  55         pthread_t       pthread_save;
  56
  57         /*
  58          * Defer signals to protect the scheduling queues from access
  59          * by the signal handler:
  60          */
  61         _thread_kern_sig_defer();
  62
  63         _pthread_mutex_lock(&_atfork_mutex);
  64
  65         /* Run down atfork prepare handlers. */
  66         TAILQ_FOREACH_REVERSE(af, &_atfork_list, atfork_head, qe) {
  67                 if (af->prepare != NULL)
  68                         af->prepare();
  69         }
  70
  71         /* Fork a new process: */
  72         if ((ret = __sys_fork()) != 0) {
  73                 /* Run down atfork parent handlers. */
  74                 TAILQ_FOREACH(af, &_atfork_list, qe) {
  75                         if (af->parent != NULL)
  76                         af->parent();
  77                 }
  78                 _pthread_mutex_unlock(&_atfork_mutex);
  79
  80         } else {
  81                 /* Close the pthread kernel pipe: */
  82                 __sys_close(_thread_kern_pipe[0]);
  83                 __sys_close(_thread_kern_pipe[1]);
  84
  85                 /* Reset signals pending for the running thread: */
  86                 sigemptyset(&curthread->sigpend);
  87
  88                 /*
  89                  * Create a pipe that is written to by the signal handler to
  90                  * prevent signals being missed in calls to
  91                  * __sys_select:
  92                  */
  93                 if (__sys_pipe(_thread_kern_pipe) != 0) {
  94                         /* Cannot create pipe, so abort: */
  95                         PANIC("Cannot create pthread kernel pipe for forked process");
  96                 }
  97                 /* Get the flags for the read pipe: */
  98                 else if ((flags = __sys_fcntl(_thread_kern_pipe[0], F_GETFL, NULL)) == -1) {
  99                         /* Abort this application: */
 100                         abort();
 101                 }
 102                 /* Make the read pipe non-blocking: */
 103                 else if (__sys_fcntl(_thread_kern_pipe[0], F_SETFL, flags | O_NONBLOCK) == -1) {
 104                         /* Abort this application: */
 105                         abort();
 106                 }
 107                 /* Get the flags for the write pipe: */
 108                 else if ((flags = __sys_fcntl(_thread_kern_pipe[1], F_GETFL, NULL)) == -1) {
 109                         /* Abort this application: */
 110                         abort();
 111                 }
 112                 /* Make the write pipe non-blocking: */
 113                 else if (__sys_fcntl(_thread_kern_pipe[1], F_SETFL, flags | O_NONBLOCK) == -1) {
 114                         /* Abort this application: */
 115                         abort();
 116                 }
 117                 /* Reinitialize the GC mutex: */
 118                 else if (_mutex_reinit(&_gc_mutex) != 0) {
 119                         /* Abort this application: */
 120                         PANIC("Cannot initialize GC mutex for forked process");
 121                 }
 122                 /* Reinitialize the GC condition variable: */
 123                 else if (_cond_reinit(&_gc_cond) != 0) {
 124                         /* Abort this application: */
 125                         PANIC("Cannot initialize GC condvar for forked process");
 126                 }
 127                 /* Initialize the ready queue: */
 128                 else if (_pq_init(&_readyq) != 0) {
 129                         /* Abort this application: */
 130                         PANIC("Cannot initialize priority ready queue.");
 131                 } else {
 132                         /*
 133                          * Enter a loop to remove all threads other than
 134                          * the running thread from the thread list:
 135                          */
 136                         if ((pthread = TAILQ_FIRST(&_thread_list)) == NULL) {
 137                                 pthread = TAILQ_FIRST(&_dead_list);
 138                                 use_deadlist = 1;
 139                         }
 140                         while (pthread != NULL) {
 141                                 /* Save the thread to be freed: */
 142                                 pthread_save = pthread;
 143
 144                                 /*
 145                                  * Advance to the next thread before
 146                                  * destroying the current thread:
 147                                  */
 148                                 if (use_deadlist != 0)
 149                                         pthread = TAILQ_NEXT(pthread, dle);
 150                                 else
 151                                         pthread = TAILQ_NEXT(pthread, tle);
 152
 153                                 /* Make sure this isn't the running thread: */
 154                                 if (pthread_save != curthread) {
 155                                         /*
 156                                          * Remove this thread from the
 157                                          * appropriate list:
 158                                          */
 159                                         if (use_deadlist != 0)
 160                                                 TAILQ_REMOVE(&_thread_list,
 161                                                     pthread_save, dle);
 162                                         else
 163                                                 TAILQ_REMOVE(&_thread_list,
 164                                                     pthread_save, tle);
 165
 166                                         free_thread_resources(pthread_save);
 167                                 }
 168
 169                                 /*
 170                                  * Switch to the deadlist when the active
 171                                  * thread list has been consumed.  This can't
 172                                  * be at the top of the loop because it is
 173                                  * used to determine to which list the thread
 174                                  * belongs (when it is removed from the list).
 175                                  */
 176                                 if (pthread == NULL) {
 177                                         pthread = TAILQ_FIRST(&_dead_list);
 178                                         use_deadlist = 1;
 179                                 }
 180                         }
 181
 182                         /* Treat the current thread as the initial thread: */
 183                         _thread_initial = curthread;
 184
 185                         /* Re-init the dead thread list: */
 186                         TAILQ_INIT(&_dead_list);
 187
 188                         /* Re-init the waiting and work queues. */
 189                         TAILQ_INIT(&_waitingq);
 190                         TAILQ_INIT(&_workq);
 191
 192                         /* Re-init the threads mutex queue: */
 193                         TAILQ_INIT(&curthread->mutexq);
 194
 195                         /* No spinlocks yet: */
 196                         _spinblock_count = 0;
 197
 198                         /* Don't queue signals yet: */
 199                         _queue_signals = 0;
 200
 201                         /* Initialize the scheduling switch hook routine: */
 202                         _sched_switch_hook = NULL;
 203
 204                         /* Clear out any locks in the file descriptor table: */
 205                         for (i = 0; i < _thread_dtablesize; i++) {
 206                                 if (_thread_fd_table[i] != NULL) {
 207                                         /* Initialise the file locks: */
 208                                         memset(&_thread_fd_table[i]->lock, 0,
 209                                             sizeof(_thread_fd_table[i]->lock));
 210                                         _thread_fd_table[i]->r_owner = NULL;
 211                                         _thread_fd_table[i]->w_owner = NULL;
 212                                         _thread_fd_table[i]->r_fname = NULL;
 213                                         _thread_fd_table[i]->w_fname = NULL;
 214                                         _thread_fd_table[i]->r_lineno = 0;;
 215                                         _thread_fd_table[i]->w_lineno = 0;;
 216                                         _thread_fd_table[i]->r_lockcount = 0;;
 217                                         _thread_fd_table[i]->w_lockcount = 0;;
 218
 219                                         /* Initialise the read/write queues: */
 220                                         TAILQ_INIT(&_thread_fd_table[i]->r_queue);
 221                                         TAILQ_INIT(&_thread_fd_table[i]->w_queue);
 222                                 }
 223                         }
 224                 }
 225                 /* Run down atfork child handlers. */
 226                 TAILQ_FOREACH(af, &_atfork_list, qe) {
 227                         if (af->child != NULL)
 228                                 af->child();
 229                 }
 230                 _mutex_reinit(&_atfork_mutex);
 231         }
 232
 233
 234         /*
 235          * Undefer and handle pending signals, yielding if necessary:
 236          */
 237         _thread_kern_sig_undefer();
 238
 239         /* Return the process ID: */
 240         return (ret);
 241 }
 242
 243 static void
 244 free_thread_resources(struct pthread *thread)
 245 {
 246
 247         /* Check to see if the threads library allocated the stack. */
 248         if ((thread->attr.stackaddr_attr == NULL) && (thread->stack != NULL)) {
 249                 /*
 250                  * Since this is being called from fork, we are currently single
 251                  * threaded so there is no need to protect the call to
 252                  * _thread_stack_free() with _gc_mutex.
 253                  */
 254                 _thread_stack_free(thread->stack, thread->attr.stacksize_attr,
 255                     thread->attr.guardsize_attr);
 256         }
 257
 258         if (thread->specific != NULL)
 259                 free(thread->specific);
 260
 261         if (thread->poll_data.fds != NULL)
 262                 free(thread->poll_data.fds);
 263
 264         free(thread);
 265 }