fail to stop daemon-server

[wangwang3210]

Found a bug in function daemon_start from libdaemon/server/daemon-server.c. It may occur in daemons like lvmetad, lvmlockd, lvmpolld.
In stable-2.02 branch, if we use the daemon lvmetad without -t option. when lvmetad is running a sub process, if the daemon recieve a SIGTERM from systemd. _shutdown_requested will turn to 1, s.threads->next is not NULL, then the while loop could not break, in the next loop, select will be blocked. Sometimes, it will lead to timeout of shutdown machine.
It could be reproduced following the steps:
1.run process 1 like,

while :
do
    lvs
done

2.run process 2 like,

while : 
do 
    service lvm2-lvmetad stop
    if [ $? -ne 0 ];then 
        echo "fail to stop"
        break
    fi
    sleep 2
done

3.soon, process 2 will be blocked, then press "CTRL+C" to stop process 1, we will see process still blocke there. Using gdb attach to lvm2-lvmetad daemon, we will see, lvm2-lvmetad blocket in select function of daemon_start. Although, at this time, _shutdown_requested is 1, s.threads->next is NULL(the _client_thread thread has already quit).

Suggested patch:

diff --git a/libdaemon/server/daemon-server.c b/libdaemon/server/daemon-server.c
index a2216ac..c753473 100644
--- a/libdaemon/server/daemon-server.c
+++ b/libdaemon/server/daemon-server.c
@@ -559,6 +559,8 @@ void daemon_start(daemon_state s)
        thread_state _threads = { .next = NULL };
        unsigned timeout_count = 0;
        fd_set in;
+ struct timeval slect_timeout = { .tv_sec = 1, .tv_usec = 0 };
+        struct timeval *ptimeout;
 
        /*
         * Switch to C locale to avoid reading large locale-archive file used by
@@ -643,9 +645,15 @@ void daemon_start(daemon_state s)
 
        while (!failed) {
                _reset_timeout(s);
+                slect_timeout.tv_sec = 1;
+                slect_timeout.tv_usec = 0;
                FD_ZERO(&in);
                FD_SET(s.socket_fd, &in);
-           if (select(FD_SETSIZE, &in, NULL, NULL, _get_timeout(s)) < 0 && errno != EINTR)
+                ptimeout = _get_timeout(s);
+         if (_shutdown_requested && !ptimeout)
+                 ptimeout = &slect_timeout;
+
+         if (select(FD_SETSIZE, &in, NULL, NULL, ptimeout) < 0 && errno != EINTR)
                        perror("select error");
                if (FD_ISSET(s.socket_fd, &in)) {
                        timeout_count = 0;

[zkabelac]

This does not look as a correct solution - but rather a race 'shift' to lower the chances to hit it - but IMHO it should be handled properly with pselect(). - I'll take a look if there is an easy way to provide correct patch.

[zkabelac]

Already fixed upstream with 44cfa55 and few follow up patches.