event: fix monitoring of the monitor process on Illuminos

Using read(0) will return 0 on Illuminos, even if there is no data.
Request at least one byte. I hope I don't break something else by
doing that.

diff --git a/src/daemon/event.c b/src/daemon/event.c
index 59a4ac0923f7824b9442ef21c6ea9f6f10cff7d0..a1f8bd813dc8e6845c2e0ae644c41264a6987715 100644 (file)
--- a/src/daemon/event.c
+++ b/src/daemon/event.c
@@ -431,7 +431,7 @@ levent_priv(evutil_socket_t fd, short what, void *arg)
        /* Check if we have some data available. We need to pass the socket in
         * non-blocking mode to be able to run the check without disruption. */
        levent_make_socket_nonblocking(fd);
-       n = read(fd, &one, 0); err = errno;
+       n = read(fd, &one, 1); err = errno;
        levent_make_socket_blocking(fd);
 
        switch (n) {
@@ -445,11 +445,10 @@ levent_priv(evutil_socket_t fd, short what, void *arg)
                log_warnx("event", "monitor process has terminated, exit");
                break;
        default:
-               /* Unfortunately, dead code, if we have data, we have requested
-                * 0 byte, so we will fall in the previous case. It seems safer
-                * to ask for 0 byte than asking for 1 byte. In the later case,
-                * if we have to speak with the monitor again before exiting, we
-                * would be out of sync. */
+               /* This is a bit unsafe as we are now out-of-sync with the
+                * monitor. It would be safer to request 0 byte, but some OS
+                * (Illuminos) seem to take the shortcut that by asking 0 byte,
+                * we can just return 0 byte. */
                log_warnx("event", "received unexpected data from monitor process, exit");
                break;
        }