freebsd-dev/lib/libc_r/uthread/uthread_fork.c

/*
 * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by John Birrell.
 * 4. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * $FreeBSD$
 */
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"

pid_t
fork(void)
{
	int             i, flags;
	pid_t           ret;
	pthread_t	pthread;
	pthread_t	pthread_save;

	/*
	 * Defer signals to protect the scheduling queues from access
	 * by the signal handler:
	 */
	_thread_kern_sig_defer();

	/* Fork a new process: */
	if ((ret = _thread_sys_fork()) != 0) {
		/* Parent process or error. Nothing to do here. */
	} else {
		/* Close the pthread kernel pipe: */
		_thread_sys_close(_thread_kern_pipe[0]);
		_thread_sys_close(_thread_kern_pipe[1]);

		/* Reset signals pending for the running thread: */
		sigemptyset(&_thread_run->sigpend);

		/*
		 * Create a pipe that is written to by the signal handler to
		 * prevent signals being missed in calls to
		 * _thread_sys_select: 
		 */
		if (_thread_sys_pipe(_thread_kern_pipe) != 0) {
			/* Cannot create pipe, so abort: */
			PANIC("Cannot create pthread kernel pipe for forked process");
		}
		/* Get the flags for the read pipe: */
		else if ((flags = _thread_sys_fcntl(_thread_kern_pipe[0], F_GETFL, NULL)) == -1) {
			/* Abort this application: */
			abort();
		}
		/* Make the read pipe non-blocking: */
		else if (_thread_sys_fcntl(_thread_kern_pipe[0], F_SETFL, flags | O_NONBLOCK) == -1) {
			/* Abort this application: */
			abort();
		}
		/* Get the flags for the write pipe: */
		else if ((flags = _thread_sys_fcntl(_thread_kern_pipe[1], F_GETFL, NULL)) == -1) {
			/* Abort this application: */
			abort();
		}
		/* Make the write pipe non-blocking: */
		else if (_thread_sys_fcntl(_thread_kern_pipe[1], F_SETFL, flags | O_NONBLOCK) == -1) {
			/* Abort this application: */
			abort();
		}
		/* Reinitialize the GC mutex: */
		else if (_mutex_reinit(&_gc_mutex) != 0) {
			/* Abort this application: */
			PANIC("Cannot initialize GC mutex for forked process");
		}
		/* Reinitialize the GC condition variable: */
		else if (_cond_reinit(&_gc_cond) != 0) {
			/* Abort this application: */
			PANIC("Cannot initialize GC condvar for forked process");
		}
		/* Initialize the ready queue: */
		else if (_pq_init(&_readyq) != 0) {
			/* Abort this application: */
			PANIC("Cannot initialize priority ready queue.");
		} else {
			/*
			 * Enter a loop to remove all threads other than
			 * the running thread from the thread list:
			 */
			pthread = TAILQ_FIRST(&_thread_list);
			while (pthread != NULL) {
				/* Save the thread to be freed: */
				pthread_save = pthread;

				/*
				 * Advance to the next thread before
				 * destroying the current thread:
				 */
				pthread = TAILQ_NEXT(pthread, dle);

				/* Make sure this isn't the running thread: */
				if (pthread_save != _thread_run) {
					/* Remove this thread from the list: */
					TAILQ_REMOVE(&_thread_list,
					    pthread_save, tle);

					if (pthread_save->attr.stackaddr_attr ==
					    NULL && pthread_save->stack != NULL)
						if (pthread_save->attr.stacksize_attr
						    == PTHREAD_STACK_DEFAULT) {
							/*
							 * Default-size stack.  Cache
							 * it:
							 */
							struct stack	*spare_stack;

							spare_stack
							    = (pthread_save->stack
							       + PTHREAD_STACK_DEFAULT
							       - sizeof(struct stack));
							SLIST_INSERT_HEAD(
							    &_stackq,
						  	    spare_stack,
							    qe);
						} else
							/*
							 * Free the stack of
							 * the dead thread:
							 */
							free(pthread_save->stack);

					if (pthread_save->specific_data != NULL)
						free(pthread_save->specific_data);

					if (pthread_save->poll_data.fds != NULL)
						free(pthread_save->poll_data.fds);

					free(pthread_save);
				}
			}

			/* Treat the current thread as the initial thread: */
			_thread_initial = _thread_run;

			/* Re-init the dead thread list: */
			TAILQ_INIT(&_dead_list);

			/* Re-init the waiting and work queues. */
			TAILQ_INIT(&_waitingq);
			TAILQ_INIT(&_workq);

			/* Re-init the threads mutex queue: */
			TAILQ_INIT(&_thread_run->mutexq);

			/* No spinlocks yet: */
			_spinblock_count = 0;

			/* Don't queue signals yet: */
			_queue_signals = 0;

			/* Initialize signal handling: */
			_thread_sig_init();

			/* Initialize the scheduling switch hook routine: */
			_sched_switch_hook = NULL;

			/* Clear out any locks in the file descriptor table: */
			for (i = 0; i < _thread_dtablesize; i++) {
				if (_thread_fd_table[i] != NULL) {
					/* Initialise the file locks: */
					memset(&_thread_fd_table[i]->lock, 0,
					    sizeof(_thread_fd_table[i]->lock));
					_thread_fd_table[i]->r_owner = NULL;
					_thread_fd_table[i]->w_owner = NULL;
					_thread_fd_table[i]->r_fname = NULL;
					_thread_fd_table[i]->w_fname = NULL;
					_thread_fd_table[i]->r_lineno = 0;;
					_thread_fd_table[i]->w_lineno = 0;;
					_thread_fd_table[i]->r_lockcount = 0;;
					_thread_fd_table[i]->w_lockcount = 0;;

					/* Initialise the read/write queues: */
					TAILQ_INIT(&_thread_fd_table[i]->r_queue);
					TAILQ_INIT(&_thread_fd_table[i]->w_queue);
				}
			}
		}
	}

	/*
	 * Undefer and handle pending signals, yielding if necessary:
	 */
	_thread_kern_sig_undefer();

	/* Return the process ID: */
	return (ret);
}
#endif