From owner-freebsd-current@FreeBSD.ORG  Thu Oct 13 12:54:18 2011
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From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= <des@des.no>
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Date: Thu, 13 Oct 2011 14:54:16 +0200
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Cc: pjd@freebsd.org
Subject: Re: incorrect use of pidfile(3)
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--=-=-=
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After discussing this with pjd@ on IRC, I arrived at the attached patch,
which increases the length of time pidfile_open() itself waits (I hadn't
noticed that it already looped) and sets *pidptr to -1 if it fails to read
a pid.

DES
--=20
Dag-Erling Sm=C3=B8rgrav - des@des.no


--=-=-=
Content-Type: text/x-patch
Content-Disposition: inline; filename=pidfile_open-loop.diff

Index: lib/libutil/pidfile.c
===================================================================
--- lib/libutil/pidfile.c	(revision 226271)
+++ lib/libutil/pidfile.c	(working copy)
@@ -118,22 +118,19 @@
 	 */
 	fd = flopen(pfh->pf_path,
 	    O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, mode);
-	if (fd == -1) {
-		count = 0;
+	if (fd == -1 && errno == EWOULDBLOCK && pidptr != NULL) {
+		*pidptr = -1;
+		count = 20;
 		rqtp.tv_sec = 0;
 		rqtp.tv_nsec = 5000000;
-		if (errno == EWOULDBLOCK && pidptr != NULL) {
-		again:
+		for (;;) {
 			errno = pidfile_read(pfh->pf_path, pidptr);
-			if (errno == 0)
-				errno = EEXIST;
-			else if (errno == EAGAIN) {
-				if (++count <= 3) {
-					nanosleep(&rqtp, 0);
-					goto again;
-				}
-			}
+			if (errno != EAGAIN || --count == 0)
+				break;
+			nanosleep(&rqtp, 0);
 		}
+		if (errno == 0)
+			errno = EEXIST;
 		free(pfh);
 		return (NULL);
 	}

--=-=-=--