freebsd-dev/lib/libkse/thread/thr_find_thread.c
Jason Evans 651974ee92 Fix a race condition in pthread_join(). All of the following must occur
atomically:

1) Search _thread_list for the thread to join.
2) Search _dead_list for the thread to join.
3) Set the running thread as the joiner.

While we're at it, fix a race in the case where multiple threads try to
join on the same thread.  POSIX says that the behavior of multiple joiners
is undefined, but the fix is cheap as a result of the other fix.
2001-06-27 11:41:15 +00:00

67 lines
2.5 KiB
C

/*
* Copyright (c) 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 <pthread.h>
#include "pthread_private.h"
/* Find a thread in the linked list of active threads: */
int
_find_thread(pthread_t pthread)
{
pthread_t pthread1;
/* Check if the caller has specified an invalid thread: */
if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
/* Invalid thread: */
return(EINVAL);
/*
* Defer signals to protect the thread list from access
* by the signal handler:
*/
_thread_kern_sig_defer();
/* Search for the specified thread: */
TAILQ_FOREACH(pthread1, &_thread_list, tle) {
if (pthread == pthread1)
break;
}
/* Undefer and handle pending signals, yielding if necessary: */
_thread_kern_sig_undefer();
/* Return zero if the thread exists: */
return ((pthread1 != NULL) ? 0:ESRCH);
}