Index: main/channel.c
===================================================================
--- main/channel.c	(revision 121861)
+++ main/channel.c	(working copy)
@@ -768,9 +768,29 @@
 			return NULL;
 		} else {
 			flags = fcntl(tmp->alertpipe[0], F_GETFL);
-			fcntl(tmp->alertpipe[0], F_SETFL, flags | O_NONBLOCK);
+			if (fcntl(tmp->alertpipe[0], F_SETFL, flags | O_NONBLOCK) < 0) {
+				ast_log(LOG_WARNING, "Unable to set alertpipe nonblocking! (%d: %s)\n", errno, strerror(errno));
+#ifdef HAVE_ZAPTEL
+				if (tmp->timingfd > -1)
+					close(tmp->timingfd);
+#endif
+				sched_context_destroy(tmp->sched);
+				ast_string_field_free_memory(tmp);
+				free(tmp);
+				return NULL;
+			}
 			flags = fcntl(tmp->alertpipe[1], F_GETFL);
-			fcntl(tmp->alertpipe[1], F_SETFL, flags | O_NONBLOCK);
+			if (fcntl(tmp->alertpipe[1], F_SETFL, flags | O_NONBLOCK) < 0) {
+				ast_log(LOG_WARNING, "Unable to set alertpipe nonblocking! (%d: %s)\n", errno, strerror(errno));
+#ifdef HAVE_ZAPTEL
+				if (tmp->timingfd > -1)
+					close(tmp->timingfd);
+#endif
+				sched_context_destroy(tmp->sched);
+				ast_string_field_free_memory(tmp);
+				free(tmp);
+				return NULL;
+			}
 		}
 	} else	/* Make sure we've got it done right if they don't */
 		tmp->alertpipe[0] = tmp->alertpipe[1] = -1;
@@ -1994,8 +2014,18 @@
 	
 	/* Read and ignore anything on the alertpipe, but read only
 	   one sizeof(blah) per frame that we send from it */
-	if (chan->alertpipe[0] > -1)
+	if (chan->alertpipe[0] > -1) {
+		int flags = fcntl(chan->alertpipe[0], F_GETFL);
+		if ((flags & O_NONBLOCK) == 0) {
+			ast_log(LOG_ERROR, "Alertpipe on channel %s lost O_NONBLOCK?!!\n", chan->name);
+			if (fcntl(chan->alertpipe[0], F_SETFL, flags | O_NONBLOCK) == 0) {
+				ast_log(LOG_WARNING, "Unable to set alertpipe nonblocking! (%d: %s)\n", errno, strerror(errno));
+				f = &ast_null_frame;
+				goto done;
+			}
+		}
 		read(chan->alertpipe[0], &blah, sizeof(blah));
+	}
 
 #ifdef HAVE_ZAPTEL
 	if (chan->timingfd > -1 && chan->fdno == AST_TIMING_FD && ast_test_flag(chan, AST_FLAG_EXCEPTION)) {