freebsd-dev/lib/libpthread/thread/thr_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 <sys/param.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <pthread.h>
#include "thr_private.h"

static void	free_thread_resources(struct pthread *thread);

__weak_reference(_fork, fork);

pid_t
_fork(void)
{
	struct pthread	*curthread = _get_curthread();
	int             i, flags, use_deadlist = 0;
	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 = __sys_fork()) != 0) {
		/* Parent process or error. Nothing to do here. */
	} else {
		/* Reinitialize the GC mutex: */
		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:
			 */
			if ((pthread = TAILQ_FIRST(&_thread_list)) == NULL) {
				pthread = TAILQ_FIRST(&_dead_list);
				use_deadlist = 1;
			}
			while (pthread != NULL) {
				/* Save the thread to be freed: */
				pthread_save = pthread;

				/*
				 * Advance to the next thread before
				 * destroying the current thread:
				 */
				if (use_deadlist != 0)
					pthread = TAILQ_NEXT(pthread, dle);
				else
					pthread = TAILQ_NEXT(pthread, tle);

				/* Make sure this isn't the running thread: */
				if (pthread_save != curthread) {
					/*
					 * Remove this thread from the
					 * appropriate list:
					 */
					if (use_deadlist != 0)
						TAILQ_REMOVE(&_thread_list,
						    pthread_save, dle);
					else
						TAILQ_REMOVE(&_thread_list,
						    pthread_save, tle);

					free_thread_resources(pthread_save);
				}

				/*
				 * Switch to the deadlist when the active
				 * thread list has been consumed.  This can't
				 * be at the top of the loop because it is
				 * used to determine to which list the thread
				 * belongs (when it is removed from the list).
				 */
				if (pthread == NULL) {
					pthread = TAILQ_FIRST(&_dead_list);
					use_deadlist = 1;
				}
			}

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

			/* 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(&curthread->mutexq);

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

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

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

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

static void
free_thread_resources(struct pthread *thread)
{

	/* Check to see if the threads library allocated the stack. */
	if ((thread->attr.stackaddr_attr == NULL) && (thread->stack != NULL)) {
		/*
		 * Since this is being called from fork, we are currently single
		 * threaded so there is no need to protect the call to
		 * _thread_stack_free() with _gc_mutex.
		 */
		_thread_stack_free(thread->stack, thread->attr.stacksize_attr,
		    thread->attr.guardsize_attr);
	}

	if (thread->specific != NULL)
		free(thread->specific);

	free(thread);
}