[hackers] [PATCH][ubase] respawn: reopen the fifo at end of line, and use read-only

[Mattias Andrée]

Signed-off-by: Mattias Andrée <maand...@kth.se>
---
 respawn.c | 35 +++++++++++++++++++++--------------
 1 file changed, 21 insertions(+), 14 deletions(-)

diff --git a/respawn.c b/respawn.c
index 77670f5..7fdd1ec 100644
--- a/respawn.c
+++ b/respawn.c
@@ -1,5 +1,4 @@
 /* See LICENSE file for copyright and license details. */
-#include <sys/select.h>
 #include <sys/stat.h>
 #include <sys/time.h>
 #include <sys/types.h>
@@ -7,6 +6,7 @@
 
 #include <errno.h>
 #include <fcntl.h>
+#include <poll.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -37,9 +37,9 @@ main(int argc, char *argv[])
        pid_t pid;
        char buf[BUFSIZ];
        int savederrno;
-       int fd;
        ssize_t n;
-       fd_set rdfd;
+       struct pollfd pollset[1];
+       int polln;
 
        ARGBEGIN {
        case 'd':
@@ -63,26 +63,33 @@ main(int argc, char *argv[])
        signal(SIGTERM, sigterm);
 
        if (fifo) {
-               /* TODO: we should use O_RDONLY and re-open the fd on EOF */
-               fd = open(fifo, O_RDWR | O_NONBLOCK);
-               if (fd < 0)
+               pollset->fd = open(fifo, O_RDONLY | O_NONBLOCK);
+               if (pollset->fd < 0)
                        eprintf("open %s:", fifo);
+               pollset->events = POLLIN;
        }
 
        while (1) {
                if (fifo) {
-                       FD_ZERO(&rdfd);
-                       FD_SET(fd, &rdfd);
-                       n = select(fd + 1, &rdfd, NULL, NULL, NULL);
-                       if (n < 0)
-                               eprintf("select:");
-                       if (n == 0 || FD_ISSET(fd, &rdfd) == 0)
-                               continue;
-                       while ((n = read(fd, buf, sizeof(buf))) > 0)
+                       pollset->revents = 0;
+                       polln = poll(pollset, 1, -1);
+                       if (polln <= 0) {
+                               if (polln == 0 || errno == EAGAIN)
+                                       continue;
+                               eprintf("poll:");
+                       }
+                       while ((n = read(pollset->fd, buf, sizeof(buf))) > 0)
                                ;
                        if (n < 0)
                                if (errno != EAGAIN)
                                        eprintf("read %s:", fifo);
+                       if (n == 0) {
+                               close(pollset->fd);
+                               pollset->fd = open(fifo, O_RDONLY | O_NONBLOCK);
+                               if (pollset->fd < 0)
+                                       eprintf("open %s:", fifo);
+                               pollset->events = POLLIN;
+                       }
                }
                pid = fork();
                if (pid < 0)
-- 
2.10.0