Update pidfile module from FreeBSD

Use EINVAL instead of EDOOFUS. Add a missing synopsis for
pidfile_fileno() in the man page. Move the definition of struct pidfh
from libutil.h into pidfile.c following upstream change.

src/pidfile.c

@@ -29,20 +29,27 @@
 #include <sys/file.h>
 #include <sys/stat.h>
 
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <fcntl.h>
-#include <string.h>
-#include <time.h>
 #include <err.h>
 #include <errno.h>
+#include <fcntl.h>
 #include <libutil.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+
+struct pidfh {
+	int	pf_fd;
+	char	*pf_path;
+	dev_t	pf_dev;
+	ino_t	pf_ino;
+};
 
 static int _pidfile_remove(struct pidfh *pfh, int freeit);
 
 static int
-pidfile_verify(struct pidfh *pfh)
+pidfile_verify(const struct pidfh *pfh)
 {
 	struct stat sb;
 
@@ -114,25 +121,33 @@ pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
 	fd = flopen(pfh->pf_path,
 	    O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, mode);
 	if (fd == -1) {
-		count = 0;
-		rqtp.tv_sec = 0;
-		rqtp.tv_nsec = 5000000;
-		if (errno == EWOULDBLOCK && pidptr != NULL) {
-		again:
-			errno = pidfile_read(pfh->pf_path, pidptr);
-			if (errno == 0)
+		if (errno == EWOULDBLOCK) {
+			if (pidptr == NULL) {
 				errno = EEXIST;
-			else if (errno == EAGAIN) {
-				if (++count <= 3) {
+			} else {
+				count = 20;
+				rqtp.tv_sec = 0;
+				rqtp.tv_nsec = 5000000;
+				for (;;) {
+					errno = pidfile_read(pfh->pf_path,
+					                     pidptr);
+					if (errno != EAGAIN || --count == 0)
+						break;
 					nanosleep(&rqtp, 0);
-					goto again;
 				}
+				if (errno == EAGAIN)
+					*pidptr = -1;
+				if (errno == 0 || errno == EAGAIN)
+					errno = EEXIST;
 			}
 		}
+		error = errno;
 		free(pfh->pf_path);
 		free(pfh);
+		errno = error;
 		return (NULL);
 	}
+
 	/*
 	 * Remember file information, so in pidfile_write() we are sure we write
 	 * to the proper descriptor.
@@ -251,3 +266,14 @@ pidfile_remove(struct pidfh *pfh)
 
 	return (_pidfile_remove(pfh, 1));
 }
+
+int
+pidfile_fileno(const struct pidfh *pfh)
+{
+
+	if (pfh == NULL || pfh->pf_fd == -1) {
+		errno = EINVAL;
+		return (-1);
+	}
+	return (pfh->pf_fd);
+}