More sync with freebsd code; join related code this time.

20 files changed, 432 insertions, 292 deletions

diff --git a/lib/libc_r/uthread/pthread_private.h b/lib/libc_r/uthread/pthread_private.h
index a07ebaf431d..b5556c44ffe 100644
--- a/lib/libc_r/uthread/pthread_private.h
+++ b/lib/libc_r/uthread/pthread_private.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pthread_private.h,v 1.30 2001/12/08 14:51:36 fgsch Exp $	*/
+/*	$OpenBSD: pthread_private.h,v 1.31 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
@@ -538,6 +538,12 @@ typedef void	(*thread_continuation_t) (void *);
 
 typedef V_TAILQ_ENTRY(pthread) pthread_entry_t;
 
+struct join_status {
+	struct pthread	*thread;
+	void		*ret;
+	int		error;
+};
+
 /*
  * Thread structure.
  */
@@ -638,8 +644,12 @@ struct pthread {
 	 */
 	int	error;
 
-	/* Join queue head and link for waiting threads: */
-	V_TAILQ_HEAD(join_head, pthread)	join_queue;
+	/*
+	 * The joiner is the thread that is joining this thraed. The
+	 * join status keeps track of a join operation to another thread.
+	 */
+	struct pthread		*joiner;
+	struct join_status	join_status;
 
 	/*
 	 * The current thread can belong to only one scheduling queue at
@@ -648,8 +658,6 @@ struct pthread {
 	 *
 	 *   o A queue of threads waiting for a mutex
 	 *   o A queue of threads waiting for a condition variable
-	 *   o A queue of threads waiting for another thread to terminate
-	 *     (the join queue above)
 	 *   o A queue of threads waiting for a file descriptor lock
 	 *   o A queue of threads needing work done by the kernel thread
 	 *     (waiting for a spinlock or file I/O)
@@ -661,6 +669,9 @@ struct pthread {
 	/* Priority queue entry for this thread: */
 	pthread_entry_t		pqe;
 
+	/* Priority queue entry for this thread: */
+	pthread_entry_t		sqe;
+
 	/* Queue entry for this thread: */
 	pthread_entry_t		qe;
 
@@ -1018,7 +1029,6 @@ SCLASS int	_thread_kern_new_state
  * Function prototype definitions.
  */
 __BEGIN_DECLS
-int     _find_dead_thread(pthread_t);
 int     _find_thread(pthread_t);
 struct pthread *_get_curthread(void);
 void	_set_curthread(struct pthread *);
diff --git a/lib/libc_r/uthread/uthread_cancel.c b/lib/libc_r/uthread/uthread_cancel.c
index b536acc4b8e..8c8515dbbc7 100644
--- a/lib/libc_r/uthread/uthread_cancel.c
+++ b/lib/libc_r/uthread/uthread_cancel.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_cancel.c,v 1.7 2001/12/08 14:51:36 fgsch Exp $	*/
+/*	$OpenBSD: uthread_cancel.c,v 1.8 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * David Leonard <d@openbsd.org>, 1999. Public domain.
  */
@@ -6,7 +6,6 @@
 #include <pthread.h>
 #include "pthread_private.h"
 
-
 static void	finish_cancellation(void *arg);
 
 int
@@ -44,6 +43,7 @@ pthread_cancel(pthread)
 			case PS_FDW_WAIT:
 			case PS_POLL_WAIT:
 			case PS_SELECT_WAIT:
+				/* Remove these threads from the work queue: */
 				if ((pthread->flags & PTHREAD_FLAGS_IN_WORKQ)
 				    != 0)
 					PTHREAD_WORKQ_REMOVE(pthread);
@@ -71,6 +71,19 @@ pthread_cancel(pthread)
 				break;
 
 			case PS_JOIN:
+				/*
+				 * Disconnect the thread from the joinee and
+				 * detach:
+				 */
+				if (pthread->data.thread != NULL) {
+					pthread->data.thread->joiner = NULL;
+					pthread_detach((pthread_t)
+					    pthread->data.thread);
+				}
+				pthread->cancelflags |= PTHREAD_CANCELLING;
+				PTHREAD_NEW_STATE(pthread, PS_RUNNING);
+				break;
+
 			case PS_SUSPENDED:
 				/* Simply wake: */
 				/* XXX may be incorrect */
@@ -165,6 +178,11 @@ pthread_testcancel()
 
 	if (((curthread->cancelflags & PTHREAD_CANCEL_DISABLE) == 0) &&
 	    ((curthread->cancelflags & PTHREAD_CANCELLING) != 0)) {
+		/*
+		 * It is possible for this thread to be swapped out
+		 * while performing cancellation; do not allow it
+		 * to be cancelled again.
+		 */
 		curthread->cancelflags &= ~PTHREAD_CANCELLING;
 #ifdef notyet
 		_thread_exit_cleanup();
diff --git a/lib/libc_r/uthread/uthread_create.c b/lib/libc_r/uthread/uthread_create.c
index 5b1897b7ef4..de96d4440de 100644
--- a/lib/libc_r/uthread/uthread_create.c
+++ b/lib/libc_r/uthread/uthread_create.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_create.c,v 1.16 2001/12/08 14:51:36 fgsch Exp $	*/
+/*	$OpenBSD: uthread_create.c,v 1.17 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -140,8 +140,8 @@ pthread_create(pthread_t * thread, const pthread_attr_t * attr,
 			new_thread->active_priority = new_thread->base_priority;
 			new_thread->inherited_priority = 0;
 
-			/* Initialise the join queue for the new thread: */
-			TAILQ_INIT(&(new_thread->join_queue));
+			/* Initialize joiner to NULL (no joiner): */
+			new_thread->joiner = NULL;
 
 			/* Initialize the mutex queue: */
 			TAILQ_INIT(&new_thread->mutexq);
diff --git a/lib/libc_r/uthread/uthread_detach.c b/lib/libc_r/uthread/uthread_detach.c
index d6accdc13cf..786df9d165c 100644
--- a/lib/libc_r/uthread/uthread_detach.c
+++ b/lib/libc_r/uthread/uthread_detach.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_detach.c,v 1.6 2000/01/06 07:15:05 d Exp $	*/
+/*	$OpenBSD: uthread_detach.c,v 1.7 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
@@ -41,7 +41,6 @@ int
 pthread_detach(pthread_t pthread)
 {
 	int             rval = 0;
-	pthread_t       next_thread;
 
 	/* Check for invalid calling parameters: */
 	if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
@@ -59,13 +58,20 @@ pthread_detach(pthread_t pthread)
 		 */
 		_thread_kern_sig_defer();
 
-		/* Enter a loop to bring all threads off the join queue: */
-		while ((next_thread = TAILQ_FIRST(&pthread->join_queue)) != NULL) {
-			/* Remove the thread from the queue: */
-			TAILQ_REMOVE(&pthread->join_queue, next_thread, qe);
+		/* Check if there is a joiner: */
+		if (pthread->joiner != NULL) {
+			struct pthread	*joiner = pthread->joiner;
 
-			/* Make the thread run: */
-			PTHREAD_NEW_STATE(next_thread,PS_RUNNING);
+			/* Make the thread runnable: */
+			PTHREAD_NEW_STATE(joiner, PS_RUNNING);
+
+			/* Set the return value for the woken thread: */
+			joiner->error = ESRCH;
+
+			/*
+			 * Disconnect the joiner from the thread being detached:
+			 */
+			pthread->joiner = NULL;
 		}
 
 		/*
diff --git a/lib/libc_r/uthread/uthread_exit.c b/lib/libc_r/uthread/uthread_exit.c
index c6013cbf1ea..232b55e008e 100644
--- a/lib/libc_r/uthread/uthread_exit.c
+++ b/lib/libc_r/uthread/uthread_exit.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_exit.c,v 1.13 2001/08/21 19:24:53 fgsch Exp $	*/
+/*	$OpenBSD: uthread_exit.c,v 1.14 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -146,7 +146,7 @@ void
 pthread_exit(void *status)
 {
 	struct pthread	*curthread = _get_curthread();
-	pthread_t       pthread;
+	pthread_t pthread;
 
 	/* Check if this thread is already in the process of exiting: */
 	if ((curthread->flags & PTHREAD_EXITING) != 0) {
@@ -162,11 +162,9 @@ pthread_exit(void *status)
 	while (curthread->cleanup != NULL) {
 		pthread_cleanup_pop(1);
 	}
-
 	if (curthread->attr.cleanup_attr != NULL) {
 		curthread->attr.cleanup_attr(curthread->attr.arg_attr);
 	}
-
 	/* Check if there is thread specific data: */
 	if (curthread->specific_data != NULL) {
 		/* Run the thread-specific data destructors: */
@@ -174,26 +172,6 @@ pthread_exit(void *status)
 	}
 
 	/*
-	 * Defer signals to protect the scheduling queues from access
-	 * by the signal handler:
-	 */
-	_thread_kern_sig_defer();
-
-	/* Check if there are any threads joined to this one: */
-	while ((pthread = TAILQ_FIRST(&(curthread->join_queue))) != NULL) {
-		/* Remove the thread from the queue: */
-		TAILQ_REMOVE(&curthread->join_queue, pthread, qe);
-
-		/* Wake the joined thread and let it detach this thread: */
-		PTHREAD_NEW_STATE(pthread,PS_RUNNING);
-	}
-
-	/*
-	 * Undefer and handle pending signals, yielding if necessary:
-	 */
-	_thread_kern_sig_undefer();
-
-	/*
 	 * Lock the garbage collector mutex to ensure that the garbage
 	 * collector is not using the dead thread list.
 	 */
@@ -204,20 +182,6 @@ pthread_exit(void *status)
 	TAILQ_INSERT_HEAD(&_dead_list, curthread, dle);
 
 	/*
-	 * Defer signals to protect the scheduling queues from access
-	 * by the signal handler:
-	 */
-	_thread_kern_sig_defer();
-
-	/* Remove this thread from the thread list: */
-	TAILQ_REMOVE(&_thread_list, curthread, tle);
-
-	/*
-	 * Undefer and handle pending signals, yielding if necessary:
-	 */
-	_thread_kern_sig_undefer();
-
-	/*
 	 * Signal the garbage collector thread that there is something
 	 * to clean up.
 	 */
@@ -225,17 +189,56 @@ pthread_exit(void *status)
 		PANIC("Cannot signal gc cond");
 
 	/*
-	 * Mark the thread as dead so it will not return if it
-	 * gets context switched out when the mutex is unlocked.
+	 * Avoid a race condition where a scheduling signal can occur
+	 * causing the garbage collector thread to run.  If this happens,
+	 * the current thread can be cleaned out from under us.
 	 */
-	PTHREAD_SET_STATE(curthread, PS_DEAD);
+	_thread_kern_sig_defer();
 
 	/* Unlock the garbage collector mutex: */
 	if (pthread_mutex_unlock(&_gc_mutex) != 0)
-		PANIC("Cannot lock gc mutex");
+		PANIC("Cannot unlock gc mutex");
+
+	/* Check if there is a thread joining this one: */
+	if (curthread->joiner != NULL) {
+		pthread = curthread->joiner;
+		curthread->joiner = NULL;
+
+		switch (pthread->suspended) {
+		case SUSP_JOIN:
+			/*
+			 * The joining thread is suspended.  Change the
+			 * suspension state to make the thread runnable when it
+			 * is resumed:
+			 */
+			pthread->suspended = SUSP_NO;
+			break;
+		case SUSP_NO:
+			/* Make the joining thread runnable: */
+			PTHREAD_NEW_STATE(pthread, PS_RUNNING);
+			break;
+		default:
+			PANIC("Unreachable code reached");
+		}
+
+		/* Set the return value for the joining thread: */
+		pthread->join_status.ret = curthread->ret;
+		pthread->join_status.error = 0;
+		pthread->join_status.thread = NULL;
+
+#ifdef notyet
+		/* Make this thread collectable by the garbage collector. */
+		PTHREAD_ASSERT(((curthread->attr.flags & PTHREAD_DETACHED) ==
+		    0), "Cannot join a detached thread");
+#endif
+		curthread->attr.flags |= PTHREAD_DETACHED;
+	}
+
+	/* Remove this thread from the thread list: */
+	TAILQ_REMOVE(&_thread_list, curthread, tle);
 
-	/* This this thread will never be re-scheduled. */
-	_thread_kern_sched(NULL);
+	/* This thread will never be re-scheduled. */
+	_thread_kern_sched_state(PS_DEAD, __FILE__, __LINE__);
 
 	/* This point should not be reached. */
 	PANIC("Dead thread has resumed");
diff --git a/lib/libc_r/uthread/uthread_find_thread.c b/lib/libc_r/uthread/uthread_find_thread.c
index 42b561524b9..c531643e325 100644
--- a/lib/libc_r/uthread/uthread_find_thread.c
+++ b/lib/libc_r/uthread/uthread_find_thread.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_find_thread.c,v 1.4 1999/11/25 07:01:35 d Exp $	*/
+/*	$OpenBSD: uthread_find_thread.c,v 1.5 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
@@ -66,36 +66,4 @@ _find_thread(pthread_t pthread)
 	/* Return zero if the thread exists: */
 	return ((pthread1 != NULL) ? 0:ESRCH);
 }
-
-/* Find a thread in the linked list of dead threads: */
-int
-_find_dead_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);
-
-	/*
-	 * Lock the garbage collector mutex to ensure that the garbage
-	 * collector is not using the dead thread list.
-	 */
-	if (pthread_mutex_lock(&_gc_mutex) != 0)
-		PANIC("Cannot lock gc mutex");
-
-	/* Search for the specified thread: */
-	TAILQ_FOREACH(pthread1, &_dead_list, dle) {
-		if (pthread1 == pthread)
-			break;
-	}
-
-	/* Unlock the garbage collector mutex: */
-	if (pthread_mutex_unlock(&_gc_mutex) != 0)
-		PANIC("Cannot lock gc mutex");
-
-	/* Return zero if the thread exists: */
-	return ((pthread1 != NULL) ? 0:ESRCH);
-}
 #endif
diff --git a/lib/libc_r/uthread/uthread_gc.c b/lib/libc_r/uthread/uthread_gc.c
index 5f4e520d6aa..956633e7fe4 100644
--- a/lib/libc_r/uthread/uthread_gc.c
+++ b/lib/libc_r/uthread/uthread_gc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_gc.c,v 1.10 2001/08/21 19:24:53 fgsch Exp $	*/
+/*	$OpenBSD: uthread_gc.c,v 1.11 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -59,8 +59,8 @@ _thread_gc(pthread_addr_t arg)
 	void		*p_stack;
 
 	/* Block all signals */
-	sigfillset (&mask);
-	sigprocmask (SIG_BLOCK, &mask, NULL);
+	sigfillset(&mask);
+	pthread_sigmask(SIG_BLOCK, &mask, NULL);
 
 	/* Mark this thread as a library thread (not a user thread). */
 	curthread->flags |= PTHREAD_FLAGS_PRIVATE;
@@ -98,6 +98,10 @@ _thread_gc(pthread_addr_t arg)
 		 */
 		_thread_kern_sig_undefer();
 
+		/* No stack of thread structure to free yet: */
+		p_stack = NULL;
+		pthread_cln = NULL;
+
 		/*
 		 * Lock the garbage collector mutex which ensures that
 		 * this thread sees another thread exit:
@@ -105,10 +109,6 @@ _thread_gc(pthread_addr_t arg)
 		if (pthread_mutex_lock(&_gc_mutex) != 0)
 			PANIC("Cannot lock gc mutex");
 
-		/* No stack of thread structure to free yet: */
-		p_stack = NULL;
-		pthread_cln = NULL;
-
 		/*
 		 * Enter a loop to search for the first dead thread that
 		 * has memory to free.
@@ -124,7 +124,7 @@ _thread_gc(pthread_addr_t arg)
 			 * Check if this thread has detached:
 			 */
 			else if ((pthread->attr.flags &
-				  PTHREAD_DETACHED) != 0) {
+			    PTHREAD_DETACHED) != 0) {
 				/* Remove this thread from the dead list: */
 				TAILQ_REMOVE(&_dead_list, pthread, dle);
 
@@ -193,13 +193,14 @@ _thread_gc(pthread_addr_t arg)
 			_thread_stack_free(p_stack);
 
 		if (pthread_cln != NULL) {
+			if (pthread_cln->name != NULL) {
+				/* Free the thread name string. */
+				free(pthread_cln->name);
+			}
 			/*
 			 * Free the memory allocated for the thread
 			 * structure.
 			 */
-			if (pthread_cln->name != NULL)
-				free(pthread_cln->name);
-
 			if (pthread_cln->poll_data.fds != NULL)
 				free(pthread_cln->poll_data.fds);
 
diff --git a/lib/libc_r/uthread/uthread_info_openbsd.c b/lib/libc_r/uthread/uthread_info_openbsd.c
index 439bf6a7655..a9f133550e9 100644
--- a/lib/libc_r/uthread/uthread_info_openbsd.c
+++ b/lib/libc_r/uthread/uthread_info_openbsd.c
@@ -1,3 +1,5 @@
+/*	$OpenBSD: uthread_info_openbsd.c,v 1.5 2001/12/11 00:19:47 fgsch Exp $	*/
+
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -29,7 +31,6 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * $OpenBSD: uthread_info_openbsd.c,v 1.4 2001/12/08 14:51:36 fgsch Exp $
  */
 #include <stdio.h>
 #include <fcntl.h>
@@ -220,6 +221,7 @@ _thread_dump_entry(pthread, fd, verbose)
 		    pthread->data.cond);
 		_thread_sys_write(fd, s, strlen(s));
 		break;
+#ifdef notyet
 	case PS_JOIN:
 		{
 			struct pthread *t, * volatile *last;
@@ -243,6 +245,7 @@ _thread_dump_entry(pthread, fd, verbose)
 			_thread_sys_write(fd, s, strlen(s));
 		}
 		break;
+#endif
 	case PS_SLEEP_WAIT:
 		{
 			struct timeval tv;
diff --git a/lib/libc_r/uthread/uthread_init.c b/lib/libc_r/uthread/uthread_init.c
index a0aaf8e8964..0c952b4130e 100644
--- a/lib/libc_r/uthread/uthread_init.c
+++ b/lib/libc_r/uthread/uthread_init.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_init.c,v 1.17 2001/12/08 14:51:36 fgsch Exp $	*/
+/*	$OpenBSD: uthread_init.c,v 1.18 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -186,8 +186,8 @@ _thread_init(void)
 		/* Initialise the state of the initial thread: */
 		_thread_initial->state = PS_RUNNING;
 
-		/* Initialise the queue: */
-		TAILQ_INIT(&(_thread_initial->join_queue));
+		/* Initialize joiner to NULL (no joiner): */
+		_thread_initial->joiner = NULL;
 
 		/* Initialize the owned mutex queue and count: */
 		TAILQ_INIT(&(_thread_initial->mutexq));
diff --git a/lib/libc_r/uthread/uthread_join.c b/lib/libc_r/uthread/uthread_join.c
index 310e5521268..1cf1624a884 100644
--- a/lib/libc_r/uthread/uthread_join.c
+++ b/lib/libc_r/uthread/uthread_join.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_join.c,v 1.7 2001/08/21 19:24:53 fgsch Exp $	*/
+/*	$OpenBSD: uthread_join.c,v 1.8 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
@@ -42,59 +42,120 @@ pthread_join(pthread_t pthread, void **thread_return)
 {
 	struct pthread	*curthread = _get_curthread();
 	int ret = 0;
+	pthread_t thread;
 
-	/* This is a cancellation point: */
 	_thread_enter_cancellation_point();
 
 	/* Check if the caller has specified an invalid thread: */
-	if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
+	if (pthread == NULL || pthread->magic != PTHREAD_MAGIC) {
 		/* Invalid thread: */
-		ret = EINVAL;
+		_thread_leave_cancellation_point();
+		return (EINVAL);
+	}
 
 	/* Check if the caller has specified itself: */
-	else if (pthread == curthread)
+	if (pthread == curthread) {
 		/* Avoid a deadlock condition: */
-		ret = EDEADLK;
+		_thread_leave_cancellation_point();
+		return (EDEADLK);
+	}
 
 	/*
-	 * Find the thread in the list of active threads or in the
-	 * list of dead threads:
+	 * Lock the garbage collector mutex to ensure that the garbage
+	 * collector is not using the dead thread list.
 	 */
-	else if (_find_thread(pthread) != 0 &&
-	    _find_dead_thread(pthread) != 0)
-		/* Return an error: */
-		ret = ESRCH;
+	if (pthread_mutex_lock(&_gc_mutex) != 0)
+		PANIC("Cannot lock gc mutex");
+
+	/*
+	 * Defer signals to protect the thread list from access
+	 * by the signal handler:
+	 */
+	_thread_kern_sig_defer();
+
+	/*
+	 * Unlock the garbage collector mutex, now that the garbage collector
+	 * can't be run:
+	 */
+	if (pthread_mutex_unlock(&_gc_mutex) != 0)
+		PANIC("Cannot unlock gc mutex");
+
+	/*
+	 * Search for the specified thread in the list of active threads.  This
+	 * is done manually here rather than calling _find_thread() because
+	 * the searches in _thread_list and _dead_list (as well as setting up
+	 * join/detach state) have to be done atomically.
+	 */
+	TAILQ_FOREACH(thread, &_thread_list, tle) {
+		if (thread == pthread)
+			break;
+	}
+	if (thread == NULL) {
+		/*
+		 * Search for the specified thread in the list of dead threads:
+		 */
+		TAILQ_FOREACH(thread, &_dead_list, dle) {
+			if (thread == pthread)
+				break;
+		}
+	}
+
+	/* Check if the thread was not found or has been detached: */
+	if (thread == NULL ||
+	    ((pthread->attr.flags & PTHREAD_DETACHED) != 0)) {
+		/* Undefer and handle pending signals, yielding if necessary: */
+		_thread_kern_sig_undefer();
 
-	/* Check if this thread has been detached: */
-	else if ((pthread->attr.flags & PTHREAD_DETACHED) != 0)
 		/* Return an error: */
 		ret = ESRCH;
 
+	} else if (pthread->joiner != NULL) {
+		/* Undefer and handle pending signals, yielding if necessary: */
+		_thread_kern_sig_undefer();
+
+		/* Multiple joiners are not supported. */
+		ret = EOPNOTSUPP;
+
 	/* Check if the thread is not dead: */
-	else if (pthread->state != PS_DEAD) {
-		/* Add the running thread to the join queue: */
-		TAILQ_INSERT_TAIL(&(pthread->join_queue), curthread, qe);
-
-		/* Schedule the next thread: */
-		_thread_kern_sched_state(PS_JOIN, __FILE__, __LINE__);
-
-		/* Check if the thread is not detached: */
-		if ((pthread->attr.flags & PTHREAD_DETACHED) == 0) {
-			/* Check if the return value is required: */
-			if (thread_return)
-				/* Return the thread's return value: */
-				*thread_return = pthread->ret;
+	} else if (pthread->state != PS_DEAD) {
+		/* Set the running thread to be the joiner: */
+		pthread->joiner = curthread;
+
+		/* Keep track of which thread we're joining to: */
+		curthread->join_status.thread = pthread;
+
+		while (curthread->join_status.thread == pthread) {
+			/* Schedule the next thread: */
+			_thread_kern_sched_state(PS_JOIN, __FILE__, __LINE__);
 		}
-		else
-			/* Return an error: */
-			ret = ESRCH;
 
-	/* Check if the return value is required: */
-	} else if (thread_return != NULL)
-		/* Return the thread's return value: */
-		*thread_return = pthread->ret;
+		/*
+		 * The thread return value and error are set by the thread we're
+		 * joining to when it exits or detaches:
+		 */
+		ret = curthread->join_status.error;
+		ret = curthread->join_status.error;
+		if ((ret == 0) && (thread_return != NULL))
+			*thread_return = curthread->join_status.ret;
+	} else {
+		/*
+		 * The thread exited (is dead) without being detached, and no
+		 * thread has joined it.
+		 */
+
+		/* Check if the return value is required: */
+		if (thread_return != NULL) {
+			/* Return the thread's return value: */
+			*thread_return = pthread->ret;
+		}
+
+		/* Make the thread collectable by the garbage collector. */
+		pthread->attr.flags |= PTHREAD_DETACHED;
+
+		/* Undefer and handle pending signals, yielding if necessary: */
+		_thread_kern_sig_undefer();
+	}
 
-	/* No longer in a cancellation point: */
 	_thread_leave_cancellation_point();
 
 	/* Return the completion status: */
diff --git a/lib/libpthread/uthread/pthread_private.h b/lib/libpthread/uthread/pthread_private.h
index a07ebaf431d..b5556c44ffe 100644
--- a/lib/libpthread/uthread/pthread_private.h
+++ b/lib/libpthread/uthread/pthread_private.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: pthread_private.h,v 1.30 2001/12/08 14:51:36 fgsch Exp $	*/
+/*	$OpenBSD: pthread_private.h,v 1.31 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
@@ -538,6 +538,12 @@ typedef void	(*thread_continuation_t) (void *);
 
 typedef V_TAILQ_ENTRY(pthread) pthread_entry_t;
 
+struct join_status {
+	struct pthread	*thread;
+	void		*ret;
+	int		error;
+};
+
 /*
  * Thread structure.
  */
@@ -638,8 +644,12 @@ struct pthread {
 	 */
 	int	error;
 
-	/* Join queue head and link for waiting threads: */
-	V_TAILQ_HEAD(join_head, pthread)	join_queue;
+	/*
+	 * The joiner is the thread that is joining this thraed. The
+	 * join status keeps track of a join operation to another thread.
+	 */
+	struct pthread		*joiner;
+	struct join_status	join_status;
 
 	/*
 	 * The current thread can belong to only one scheduling queue at
@@ -648,8 +658,6 @@ struct pthread {
 	 *
 	 *   o A queue of threads waiting for a mutex
 	 *   o A queue of threads waiting for a condition variable
-	 *   o A queue of threads waiting for another thread to terminate
-	 *     (the join queue above)
 	 *   o A queue of threads waiting for a file descriptor lock
 	 *   o A queue of threads needing work done by the kernel thread
 	 *     (waiting for a spinlock or file I/O)
@@ -661,6 +669,9 @@ struct pthread {
 	/* Priority queue entry for this thread: */
 	pthread_entry_t		pqe;
 
+	/* Priority queue entry for this thread: */
+	pthread_entry_t		sqe;
+
 	/* Queue entry for this thread: */
 	pthread_entry_t		qe;
 
@@ -1018,7 +1029,6 @@ SCLASS int	_thread_kern_new_state
  * Function prototype definitions.
  */
 __BEGIN_DECLS
-int     _find_dead_thread(pthread_t);
 int     _find_thread(pthread_t);
 struct pthread *_get_curthread(void);
 void	_set_curthread(struct pthread *);
diff --git a/lib/libpthread/uthread/uthread_cancel.c b/lib/libpthread/uthread/uthread_cancel.c
index b536acc4b8e..8c8515dbbc7 100644
--- a/lib/libpthread/uthread/uthread_cancel.c
+++ b/lib/libpthread/uthread/uthread_cancel.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_cancel.c,v 1.7 2001/12/08 14:51:36 fgsch Exp $	*/
+/*	$OpenBSD: uthread_cancel.c,v 1.8 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * David Leonard <d@openbsd.org>, 1999. Public domain.
  */
@@ -6,7 +6,6 @@
 #include <pthread.h>
 #include "pthread_private.h"
 
-
 static void	finish_cancellation(void *arg);
 
 int
@@ -44,6 +43,7 @@ pthread_cancel(pthread)
 			case PS_FDW_WAIT:
 			case PS_POLL_WAIT:
 			case PS_SELECT_WAIT:
+				/* Remove these threads from the work queue: */
 				if ((pthread->flags & PTHREAD_FLAGS_IN_WORKQ)
 				    != 0)
 					PTHREAD_WORKQ_REMOVE(pthread);
@@ -71,6 +71,19 @@ pthread_cancel(pthread)
 				break;
 
 			case PS_JOIN:
+				/*
+				 * Disconnect the thread from the joinee and
+				 * detach:
+				 */
+				if (pthread->data.thread != NULL) {
+					pthread->data.thread->joiner = NULL;
+					pthread_detach((pthread_t)
+					    pthread->data.thread);
+				}
+				pthread->cancelflags |= PTHREAD_CANCELLING;
+				PTHREAD_NEW_STATE(pthread, PS_RUNNING);
+				break;
+
 			case PS_SUSPENDED:
 				/* Simply wake: */
 				/* XXX may be incorrect */
@@ -165,6 +178,11 @@ pthread_testcancel()
 
 	if (((curthread->cancelflags & PTHREAD_CANCEL_DISABLE) == 0) &&
 	    ((curthread->cancelflags & PTHREAD_CANCELLING) != 0)) {
+		/*
+		 * It is possible for this thread to be swapped out
+		 * while performing cancellation; do not allow it
+		 * to be cancelled again.
+		 */
 		curthread->cancelflags &= ~PTHREAD_CANCELLING;
 #ifdef notyet
 		_thread_exit_cleanup();
diff --git a/lib/libpthread/uthread/uthread_create.c b/lib/libpthread/uthread/uthread_create.c
index 5b1897b7ef4..de96d4440de 100644
--- a/lib/libpthread/uthread/uthread_create.c
+++ b/lib/libpthread/uthread/uthread_create.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_create.c,v 1.16 2001/12/08 14:51:36 fgsch Exp $	*/
+/*	$OpenBSD: uthread_create.c,v 1.17 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -140,8 +140,8 @@ pthread_create(pthread_t * thread, const pthread_attr_t * attr,
 			new_thread->active_priority = new_thread->base_priority;
 			new_thread->inherited_priority = 0;
 
-			/* Initialise the join queue for the new thread: */
-			TAILQ_INIT(&(new_thread->join_queue));
+			/* Initialize joiner to NULL (no joiner): */
+			new_thread->joiner = NULL;
 
 			/* Initialize the mutex queue: */
 			TAILQ_INIT(&new_thread->mutexq);
diff --git a/lib/libpthread/uthread/uthread_detach.c b/lib/libpthread/uthread/uthread_detach.c
index d6accdc13cf..786df9d165c 100644
--- a/lib/libpthread/uthread/uthread_detach.c
+++ b/lib/libpthread/uthread/uthread_detach.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_detach.c,v 1.6 2000/01/06 07:15:05 d Exp $	*/
+/*	$OpenBSD: uthread_detach.c,v 1.7 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
@@ -41,7 +41,6 @@ int
 pthread_detach(pthread_t pthread)
 {
 	int             rval = 0;
-	pthread_t       next_thread;
 
 	/* Check for invalid calling parameters: */
 	if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
@@ -59,13 +58,20 @@ pthread_detach(pthread_t pthread)
 		 */
 		_thread_kern_sig_defer();
 
-		/* Enter a loop to bring all threads off the join queue: */
-		while ((next_thread = TAILQ_FIRST(&pthread->join_queue)) != NULL) {
-			/* Remove the thread from the queue: */
-			TAILQ_REMOVE(&pthread->join_queue, next_thread, qe);
+		/* Check if there is a joiner: */
+		if (pthread->joiner != NULL) {
+			struct pthread	*joiner = pthread->joiner;
 
-			/* Make the thread run: */
-			PTHREAD_NEW_STATE(next_thread,PS_RUNNING);
+			/* Make the thread runnable: */
+			PTHREAD_NEW_STATE(joiner, PS_RUNNING);
+
+			/* Set the return value for the woken thread: */
+			joiner->error = ESRCH;
+
+			/*
+			 * Disconnect the joiner from the thread being detached:
+			 */
+			pthread->joiner = NULL;
 		}
 
 		/*
diff --git a/lib/libpthread/uthread/uthread_exit.c b/lib/libpthread/uthread/uthread_exit.c
index c6013cbf1ea..232b55e008e 100644
--- a/lib/libpthread/uthread/uthread_exit.c
+++ b/lib/libpthread/uthread/uthread_exit.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_exit.c,v 1.13 2001/08/21 19:24:53 fgsch Exp $	*/
+/*	$OpenBSD: uthread_exit.c,v 1.14 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -146,7 +146,7 @@ void
 pthread_exit(void *status)
 {
 	struct pthread	*curthread = _get_curthread();
-	pthread_t       pthread;
+	pthread_t pthread;
 
 	/* Check if this thread is already in the process of exiting: */
 	if ((curthread->flags & PTHREAD_EXITING) != 0) {
@@ -162,11 +162,9 @@ pthread_exit(void *status)
 	while (curthread->cleanup != NULL) {
 		pthread_cleanup_pop(1);
 	}
-
 	if (curthread->attr.cleanup_attr != NULL) {
 		curthread->attr.cleanup_attr(curthread->attr.arg_attr);
 	}
-
 	/* Check if there is thread specific data: */
 	if (curthread->specific_data != NULL) {
 		/* Run the thread-specific data destructors: */
@@ -174,26 +172,6 @@ pthread_exit(void *status)
 	}
 
 	/*
-	 * Defer signals to protect the scheduling queues from access
-	 * by the signal handler:
-	 */
-	_thread_kern_sig_defer();
-
-	/* Check if there are any threads joined to this one: */
-	while ((pthread = TAILQ_FIRST(&(curthread->join_queue))) != NULL) {
-		/* Remove the thread from the queue: */
-		TAILQ_REMOVE(&curthread->join_queue, pthread, qe);
-
-		/* Wake the joined thread and let it detach this thread: */
-		PTHREAD_NEW_STATE(pthread,PS_RUNNING);
-	}
-
-	/*
-	 * Undefer and handle pending signals, yielding if necessary:
-	 */
-	_thread_kern_sig_undefer();
-
-	/*
 	 * Lock the garbage collector mutex to ensure that the garbage
 	 * collector is not using the dead thread list.
 	 */
@@ -204,20 +182,6 @@ pthread_exit(void *status)
 	TAILQ_INSERT_HEAD(&_dead_list, curthread, dle);
 
 	/*
-	 * Defer signals to protect the scheduling queues from access
-	 * by the signal handler:
-	 */
-	_thread_kern_sig_defer();
-
-	/* Remove this thread from the thread list: */
-	TAILQ_REMOVE(&_thread_list, curthread, tle);
-
-	/*
-	 * Undefer and handle pending signals, yielding if necessary:
-	 */
-	_thread_kern_sig_undefer();
-
-	/*
 	 * Signal the garbage collector thread that there is something
 	 * to clean up.
 	 */
@@ -225,17 +189,56 @@ pthread_exit(void *status)
 		PANIC("Cannot signal gc cond");
 
 	/*
-	 * Mark the thread as dead so it will not return if it
-	 * gets context switched out when the mutex is unlocked.
+	 * Avoid a race condition where a scheduling signal can occur
+	 * causing the garbage collector thread to run.  If this happens,
+	 * the current thread can be cleaned out from under us.
 	 */
-	PTHREAD_SET_STATE(curthread, PS_DEAD);
+	_thread_kern_sig_defer();
 
 	/* Unlock the garbage collector mutex: */
 	if (pthread_mutex_unlock(&_gc_mutex) != 0)
-		PANIC("Cannot lock gc mutex");
+		PANIC("Cannot unlock gc mutex");
+
+	/* Check if there is a thread joining this one: */
+	if (curthread->joiner != NULL) {
+		pthread = curthread->joiner;
+		curthread->joiner = NULL;
+
+		switch (pthread->suspended) {
+		case SUSP_JOIN:
+			/*
+			 * The joining thread is suspended.  Change the
+			 * suspension state to make the thread runnable when it
+			 * is resumed:
+			 */
+			pthread->suspended = SUSP_NO;
+			break;
+		case SUSP_NO:
+			/* Make the joining thread runnable: */
+			PTHREAD_NEW_STATE(pthread, PS_RUNNING);
+			break;
+		default:
+			PANIC("Unreachable code reached");
+		}
+
+		/* Set the return value for the joining thread: */
+		pthread->join_status.ret = curthread->ret;
+		pthread->join_status.error = 0;
+		pthread->join_status.thread = NULL;
+
+#ifdef notyet
+		/* Make this thread collectable by the garbage collector. */
+		PTHREAD_ASSERT(((curthread->attr.flags & PTHREAD_DETACHED) ==
+		    0), "Cannot join a detached thread");
+#endif
+		curthread->attr.flags |= PTHREAD_DETACHED;
+	}
+
+	/* Remove this thread from the thread list: */
+	TAILQ_REMOVE(&_thread_list, curthread, tle);
 
-	/* This this thread will never be re-scheduled. */
-	_thread_kern_sched(NULL);
+	/* This thread will never be re-scheduled. */
+	_thread_kern_sched_state(PS_DEAD, __FILE__, __LINE__);
 
 	/* This point should not be reached. */
 	PANIC("Dead thread has resumed");
diff --git a/lib/libpthread/uthread/uthread_find_thread.c b/lib/libpthread/uthread/uthread_find_thread.c
index 42b561524b9..c531643e325 100644
--- a/lib/libpthread/uthread/uthread_find_thread.c
+++ b/lib/libpthread/uthread/uthread_find_thread.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_find_thread.c,v 1.4 1999/11/25 07:01:35 d Exp $	*/
+/*	$OpenBSD: uthread_find_thread.c,v 1.5 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
@@ -66,36 +66,4 @@ _find_thread(pthread_t pthread)
 	/* Return zero if the thread exists: */
 	return ((pthread1 != NULL) ? 0:ESRCH);
 }
-
-/* Find a thread in the linked list of dead threads: */
-int
-_find_dead_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);
-
-	/*
-	 * Lock the garbage collector mutex to ensure that the garbage
-	 * collector is not using the dead thread list.
-	 */
-	if (pthread_mutex_lock(&_gc_mutex) != 0)
-		PANIC("Cannot lock gc mutex");
-
-	/* Search for the specified thread: */
-	TAILQ_FOREACH(pthread1, &_dead_list, dle) {
-		if (pthread1 == pthread)
-			break;
-	}
-
-	/* Unlock the garbage collector mutex: */
-	if (pthread_mutex_unlock(&_gc_mutex) != 0)
-		PANIC("Cannot lock gc mutex");
-
-	/* Return zero if the thread exists: */
-	return ((pthread1 != NULL) ? 0:ESRCH);
-}
 #endif
diff --git a/lib/libpthread/uthread/uthread_gc.c b/lib/libpthread/uthread/uthread_gc.c
index 5f4e520d6aa..956633e7fe4 100644
--- a/lib/libpthread/uthread/uthread_gc.c
+++ b/lib/libpthread/uthread/uthread_gc.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_gc.c,v 1.10 2001/08/21 19:24:53 fgsch Exp $	*/
+/*	$OpenBSD: uthread_gc.c,v 1.11 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -59,8 +59,8 @@ _thread_gc(pthread_addr_t arg)
 	void		*p_stack;
 
 	/* Block all signals */
-	sigfillset (&mask);
-	sigprocmask (SIG_BLOCK, &mask, NULL);
+	sigfillset(&mask);
+	pthread_sigmask(SIG_BLOCK, &mask, NULL);
 
 	/* Mark this thread as a library thread (not a user thread). */
 	curthread->flags |= PTHREAD_FLAGS_PRIVATE;
@@ -98,6 +98,10 @@ _thread_gc(pthread_addr_t arg)
 		 */
 		_thread_kern_sig_undefer();
 
+		/* No stack of thread structure to free yet: */
+		p_stack = NULL;
+		pthread_cln = NULL;
+
 		/*
 		 * Lock the garbage collector mutex which ensures that
 		 * this thread sees another thread exit:
@@ -105,10 +109,6 @@ _thread_gc(pthread_addr_t arg)
 		if (pthread_mutex_lock(&_gc_mutex) != 0)
 			PANIC("Cannot lock gc mutex");
 
-		/* No stack of thread structure to free yet: */
-		p_stack = NULL;
-		pthread_cln = NULL;
-
 		/*
 		 * Enter a loop to search for the first dead thread that
 		 * has memory to free.
@@ -124,7 +124,7 @@ _thread_gc(pthread_addr_t arg)
 			 * Check if this thread has detached:
 			 */
 			else if ((pthread->attr.flags &
-				  PTHREAD_DETACHED) != 0) {
+			    PTHREAD_DETACHED) != 0) {
 				/* Remove this thread from the dead list: */
 				TAILQ_REMOVE(&_dead_list, pthread, dle);
 
@@ -193,13 +193,14 @@ _thread_gc(pthread_addr_t arg)
 			_thread_stack_free(p_stack);
 
 		if (pthread_cln != NULL) {
+			if (pthread_cln->name != NULL) {
+				/* Free the thread name string. */
+				free(pthread_cln->name);
+			}
 			/*
 			 * Free the memory allocated for the thread
 			 * structure.
 			 */
-			if (pthread_cln->name != NULL)
-				free(pthread_cln->name);
-
 			if (pthread_cln->poll_data.fds != NULL)
 				free(pthread_cln->poll_data.fds);
 
diff --git a/lib/libpthread/uthread/uthread_info_openbsd.c b/lib/libpthread/uthread/uthread_info_openbsd.c
index 439bf6a7655..a9f133550e9 100644
--- a/lib/libpthread/uthread/uthread_info_openbsd.c
+++ b/lib/libpthread/uthread/uthread_info_openbsd.c
@@ -1,3 +1,5 @@
+/*	$OpenBSD: uthread_info_openbsd.c,v 1.5 2001/12/11 00:19:47 fgsch Exp $	*/
+
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -29,7 +31,6 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * $OpenBSD: uthread_info_openbsd.c,v 1.4 2001/12/08 14:51:36 fgsch Exp $
  */
 #include <stdio.h>
 #include <fcntl.h>
@@ -220,6 +221,7 @@ _thread_dump_entry(pthread, fd, verbose)
 		    pthread->data.cond);
 		_thread_sys_write(fd, s, strlen(s));
 		break;
+#ifdef notyet
 	case PS_JOIN:
 		{
 			struct pthread *t, * volatile *last;
@@ -243,6 +245,7 @@ _thread_dump_entry(pthread, fd, verbose)
 			_thread_sys_write(fd, s, strlen(s));
 		}
 		break;
+#endif
 	case PS_SLEEP_WAIT:
 		{
 			struct timeval tv;
diff --git a/lib/libpthread/uthread/uthread_init.c b/lib/libpthread/uthread/uthread_init.c
index a0aaf8e8964..0c952b4130e 100644
--- a/lib/libpthread/uthread/uthread_init.c
+++ b/lib/libpthread/uthread/uthread_init.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_init.c,v 1.17 2001/12/08 14:51:36 fgsch Exp $	*/
+/*	$OpenBSD: uthread_init.c,v 1.18 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
  * All rights reserved.
@@ -186,8 +186,8 @@ _thread_init(void)
 		/* Initialise the state of the initial thread: */
 		_thread_initial->state = PS_RUNNING;
 
-		/* Initialise the queue: */
-		TAILQ_INIT(&(_thread_initial->join_queue));
+		/* Initialize joiner to NULL (no joiner): */
+		_thread_initial->joiner = NULL;
 
 		/* Initialize the owned mutex queue and count: */
 		TAILQ_INIT(&(_thread_initial->mutexq));
diff --git a/lib/libpthread/uthread/uthread_join.c b/lib/libpthread/uthread/uthread_join.c
index 310e5521268..1cf1624a884 100644
--- a/lib/libpthread/uthread/uthread_join.c
+++ b/lib/libpthread/uthread/uthread_join.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uthread_join.c,v 1.7 2001/08/21 19:24:53 fgsch Exp $	*/
+/*	$OpenBSD: uthread_join.c,v 1.8 2001/12/11 00:19:47 fgsch Exp $	*/
 /*
  * Copyright (c) 1995 John Birrell <jb@cimlogic.com.au>.
  * All rights reserved.
@@ -42,59 +42,120 @@ pthread_join(pthread_t pthread, void **thread_return)
 {
 	struct pthread	*curthread = _get_curthread();
 	int ret = 0;
+	pthread_t thread;
 
-	/* This is a cancellation point: */
 	_thread_enter_cancellation_point();
 
 	/* Check if the caller has specified an invalid thread: */
-	if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
+	if (pthread == NULL || pthread->magic != PTHREAD_MAGIC) {
 		/* Invalid thread: */
-		ret = EINVAL;
+		_thread_leave_cancellation_point();
+		return (EINVAL);
+	}
 
 	/* Check if the caller has specified itself: */
-	else if (pthread == curthread)
+	if (pthread == curthread) {
 		/* Avoid a deadlock condition: */
-		ret = EDEADLK;
+		_thread_leave_cancellation_point();
+		return (EDEADLK);
+	}
 
 	/*
-	 * Find the thread in the list of active threads or in the
-	 * list of dead threads:
+	 * Lock the garbage collector mutex to ensure that the garbage
+	 * collector is not using the dead thread list.
 	 */
-	else if (_find_thread(pthread) != 0 &&
-	    _find_dead_thread(pthread) != 0)
-		/* Return an error: */
-		ret = ESRCH;
+	if (pthread_mutex_lock(&_gc_mutex) != 0)
+		PANIC("Cannot lock gc mutex");
+
+	/*
+	 * Defer signals to protect the thread list from access
+	 * by the signal handler:
+	 */
+	_thread_kern_sig_defer();
+
+	/*
+	 * Unlock the garbage collector mutex, now that the garbage collector
+	 * can't be run:
+	 */
+	if (pthread_mutex_unlock(&_gc_mutex) != 0)
+		PANIC("Cannot unlock gc mutex");
+
+	/*
+	 * Search for the specified thread in the list of active threads.  This
+	 * is done manually here rather than calling _find_thread() because
+	 * the searches in _thread_list and _dead_list (as well as setting up
+	 * join/detach state) have to be done atomically.
+	 */
+	TAILQ_FOREACH(thread, &_thread_list, tle) {
+		if (thread == pthread)
+			break;
+	}
+	if (thread == NULL) {
+		/*
+		 * Search for the specified thread in the list of dead threads:
+		 */
+		TAILQ_FOREACH(thread, &_dead_list, dle) {
+			if (thread == pthread)
+				break;
+		}
+	}
+
+	/* Check if the thread was not found or has been detached: */
+	if (thread == NULL ||
+	    ((pthread->attr.flags & PTHREAD_DETACHED) != 0)) {
+		/* Undefer and handle pending signals, yielding if necessary: */
+		_thread_kern_sig_undefer();
 
-	/* Check if this thread has been detached: */
-	else if ((pthread->attr.flags & PTHREAD_DETACHED) != 0)
 		/* Return an error: */
 		ret = ESRCH;
 
+	} else if (pthread->joiner != NULL) {
+		/* Undefer and handle pending signals, yielding if necessary: */
+		_thread_kern_sig_undefer();
+
+		/* Multiple joiners are not supported. */
+		ret = EOPNOTSUPP;
+
 	/* Check if the thread is not dead: */
-	else if (pthread->state != PS_DEAD) {
-		/* Add the running thread to the join queue: */
-		TAILQ_INSERT_TAIL(&(pthread->join_queue), curthread, qe);
-
-		/* Schedule the next thread: */
-		_thread_kern_sched_state(PS_JOIN, __FILE__, __LINE__);
-
-		/* Check if the thread is not detached: */
-		if ((pthread->attr.flags & PTHREAD_DETACHED) == 0) {
-			/* Check if the return value is required: */
-			if (thread_return)
-				/* Return the thread's return value: */
-				*thread_return = pthread->ret;
+	} else if (pthread->state != PS_DEAD) {
+		/* Set the running thread to be the joiner: */
+		pthread->joiner = curthread;
+
+		/* Keep track of which thread we're joining to: */
+		curthread->join_status.thread = pthread;
+
+		while (curthread->join_status.thread == pthread) {
+			/* Schedule the next thread: */
+			_thread_kern_sched_state(PS_JOIN, __FILE__, __LINE__);
 		}
-		else
-			/* Return an error: */
-			ret = ESRCH;
 
-	/* Check if the return value is required: */
-	} else if (thread_return != NULL)
-		/* Return the thread's return value: */
-		*thread_return = pthread->ret;
+		/*
+		 * The thread return value and error are set by the thread we're
+		 * joining to when it exits or detaches:
+		 */
+		ret = curthread->join_status.error;
+		ret = curthread->join_status.error;
+		if ((ret == 0) && (thread_return != NULL))
+			*thread_return = curthread->join_status.ret;
+	} else {
+		/*
+		 * The thread exited (is dead) without being detached, and no
+		 * thread has joined it.
+		 */
+
+		/* Check if the return value is required: */
+		if (thread_return != NULL) {
+			/* Return the thread's return value: */
+			*thread_return = pthread->ret;
+		}
+
+		/* Make the thread collectable by the garbage collector. */
+		pthread->attr.flags |= PTHREAD_DETACHED;
+
+		/* Undefer and handle pending signals, yielding if necessary: */
+		_thread_kern_sig_undefer();
+	}
 
-	/* No longer in a cancellation point: */
 	_thread_leave_cancellation_point();
 
 	/* Return the completion status: */