do check for utmp checking at the right time

We were doing the check for whether we need to watch utmp from a
thread cloned from that which will actually do the utmp watching.
As a result, the utmp file was always being watched, even if it
didn't need to be.

Move the check to the parent thread.

Bug-Ubuntu: https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/948623

Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>

diff --git a/src/lxc/start.c b/src/lxc/start.c
index fc2a1b148b9256cfc6355b9a4863690e0d2ffbd8..7af1e371f2af2cb583eb6cfb7bfbb99fc551152d 100644 (file)
--- a/src/lxc/start.c
+++ b/src/lxc/start.c
@@ -503,16 +503,12 @@ static int do_start(void *data)
        if (lxc_sync_barrier_parent(handler, LXC_SYNC_CONFIGURE))
                return -1;
 
-       if (must_drop_cap_sys_boot()) {
+       if (handler->conf->need_utmp_watch) {
                if (prctl(PR_CAPBSET_DROP, CAP_SYS_BOOT, 0, 0, 0)) {
                        SYSERROR("failed to remove CAP_SYS_BOOT capability");
                        return -1;
                }
-               handler->conf->need_utmp_watch = 1;
                DEBUG("Dropped cap_sys_boot\n");
-       } else {
-               DEBUG("Not dropping cap_sys_boot or watching utmp\n");
-               handler->conf->need_utmp_watch = 0;
        }
 
        /* Setup the container, ip, names, utsname, ... */
@@ -635,6 +631,14 @@ int __lxc_start(const char *name, struct lxc_conf *conf,
        handler->ops = ops;
        handler->data = data;
 
+       if (must_drop_cap_sys_boot()) {
+               handler->conf->need_utmp_watch = 1;
+               DEBUG("Dropping cap_sys_boot and watching utmp\n");
+       } else {
+               DEBUG("Not dropping cap_sys_boot or watching utmp\n");
+               handler->conf->need_utmp_watch = 0;
+       }
+
        err = lxc_spawn(handler);
        if (err) {
                ERROR("failed to spawn '%s'", name);