Do not loop on EAGAIN in imsg_read(). Better to return the error to the

caller and let him do another poll loop. This fixes spinning relayd
processes seen on busy TLS relays. OK benno@ henning@

src/lib/libutil/imsg.c

@@ -1,4 +1,4 @@
-/*	$OpenBSD: imsg.c,v 1.11 2015/11/27 01:57:59 mmcc Exp $	*/
+/*	$OpenBSD: imsg.c,v 1.12 2015/12/05 13:06:52 claudio Exp $	*/
 
 /*
  * Copyright (c) 2003, 2004 Henning Brauer <henning@openbsd.org>
@@ -80,11 +80,9 @@ again:
 	}
 
 	if ((n = recvmsg(ibuf->fd, &msg, 0)) == -1) {
-		if (errno == EMSGSIZE)
-			goto fail;
-		if (errno != EINTR && errno != EAGAIN)
-			goto fail;
-		goto again;
+		if (errno == EINTR)
+			goto again;
+		goto fail;
 	}
 
 	ibuf->r.wpos += n;

src/lib/libutil/imsg_init.3

@@ -1,4 +1,4 @@
-.\" $OpenBSD: imsg_init.3,v 1.13 2015/07/11 16:23:59 deraadt Exp $
+.\" $OpenBSD: imsg_init.3,v 1.14 2015/12/05 13:06:52 claudio Exp $
 .\"
 .\" Copyright (c) 2010 Nicholas Marriott <nicm@openbsd.org>
 .\"
@@ -14,7 +14,7 @@
 .\" IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 .\" OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: July 11 2015 $
+.Dd $Mdocdate: December 5 2015 $
 .Dt IMSG_INIT 3
 .Os
 .Sh NAME
@@ -515,7 +515,7 @@ dispatch_imsg(struct imsgbuf *ibuf)
 	ssize_t         n, datalen;
 	int		idata;
 
-	if ((n = imsg_read(ibuf)) == -1 || n == 0) {
+	if (((n = imsg_read(ibuf)) == -1 && errno != EAGAIN) || n == 0) {
 		/* handle socket error */
 	}