Fix pthread_join so that it works if the target thread exits while

the joining thread is in a signal handler.

Reported by:	Loren James Rittle <rittle@labs.mot.com>
MFC after:	1 week

4 files changed, 32 insertions, 10 deletions

diff --git a/lib/libc_r/uthread/pthread_private.h b/lib/libc_r/uthread/pthread_private.h
index 151fd03..b60d8b7 100644
--- a/lib/libc_r/uthread/pthread_private.h
+++ b/lib/libc_r/uthread/pthread_private.h
@@ -601,6 +601,11 @@ struct pthread_state_data {
 	/* XXX - What about thread->timeout and/or thread->error? */
 };
 
+struct join_status {
+	struct pthread	*thread;
+	int		ret;
+	int		error;
+};
 
 /*
  * Normally thread contexts are stored as jmp_bufs via _setjmp()/_longjmp(),
@@ -757,8 +762,12 @@ struct pthread {
 	 */
 	int	error;
 
-	/* Pointer to a thread that is waiting to join (NULL if no joiner). */
-	struct pthread *joiner;
+	/*
+	 * The joiner is the thread that is joining to this thread.  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
diff --git a/lib/libc_r/uthread/uthread_exit.c b/lib/libc_r/uthread/uthread_exit.c
index 9376350..d916f5c 100644
--- a/lib/libc_r/uthread/uthread_exit.c
+++ b/lib/libc_r/uthread/uthread_exit.c
@@ -220,8 +220,9 @@ _pthread_exit(void *status)
 		}
 
 		/* Set the return value for the joining thread: */
-		pthread->ret = curthread->ret;
-		pthread->error = 0;
+		pthread->join_status.ret = curthread->ret;
+		pthread->join_status.error = 0;
+		pthread->join_status.thread = NULL;
 
 		/* Make this thread collectable by the garbage collector. */
 		PTHREAD_ASSERT(((curthread->attr.flags & PTHREAD_DETACHED) ==
diff --git a/lib/libc_r/uthread/uthread_join.c b/lib/libc_r/uthread/uthread_join.c
index 454c79a..0f5e8fc 100644
--- a/lib/libc_r/uthread/uthread_join.c
+++ b/lib/libc_r/uthread/uthread_join.c
@@ -122,18 +122,20 @@ _pthread_join(pthread_t pthread, void **thread_return)
 		pthread->joiner = curthread;
 
 		/* Keep track of which thread we're joining to: */
-		curthread->data.thread = pthread;
+		curthread->join_status.thread = pthread;
 
-		/* Schedule the next thread: */
-		_thread_kern_sched_state(PS_JOIN, __FILE__, __LINE__);
+		while (curthread->join_status.thread == pthread) {
+			/* Schedule the next thread: */
+			_thread_kern_sched_state(PS_JOIN, __FILE__, __LINE__);
+		}
 
 		/*
 		 * The thread return value and error are set by the thread we're
 		 * joining to when it exits or detaches:
 		 */
-		ret = curthread->error;
+		ret = curthread->join_status.error;
 		if ((ret == 0) && (thread_return != NULL))
-			*thread_return = curthread->ret;
+			*thread_return = curthread->join_status.ret;
 	} else {
 		/*
 		 * The thread exited (is dead) without being detached, and no
diff --git a/lib/libc_r/uthread/uthread_sig.c b/lib/libc_r/uthread/uthread_sig.c
index 9ca197e..a05f914 100644
--- a/lib/libc_r/uthread/uthread_sig.c
+++ b/lib/libc_r/uthread/uthread_sig.c
@@ -671,7 +671,6 @@ thread_sig_add(pthread_t pthread, int sig, int has_args)
 	 * signal handler to run:
 	 */
 	case PS_COND_WAIT:
-	case PS_JOIN:
 	case PS_MUTEX_WAIT:
 		/*
 		 * Remove the thread from the wait queue.  It will
@@ -681,6 +680,17 @@ thread_sig_add(pthread_t pthread, int sig, int has_args)
 		PTHREAD_WAITQ_REMOVE(pthread);
 		break;
 
+	case PS_JOIN:
+		/*
+		 * Remove the thread from the wait queue.  It will
+		 * be added back to the wait queue once all signal
+		 * handlers have been invoked.
+		 */
+		PTHREAD_WAITQ_REMOVE(pthread);
+		/* Make the thread runnable: */
+		PTHREAD_SET_STATE(pthread, PS_RUNNING);
+		break;
+
 	/*
 	 * States which are interruptible but may need to be removed
 	 * from queues before any signal handler is called.