(#2174645) Make sure journalctl --flush does not hang

src/journal/journald-server.c

@@ -1188,6 +1188,7 @@ int server_process_datagram(sd_event_source *es, int fd, uint32_t revents, void
 
 static int dispatch_sigusr1(sd_event_source *es, const struct signalfd_siginfo *si, void *userdata) {
         Server *s = userdata;
+        int r;
 
         assert(s);
 
@@ -1197,6 +1198,10 @@ static int dispatch_sigusr1(sd_event_source *es, const struct signalfd_siginfo *
         server_sync(s);
         server_vacuum(s, false);
 
+        r = touch("/run/systemd/journal/flushed");
+        if (r < 0)
+                log_warning_errno(r, "Failed to touch /run/systemd/journal/flushed, ignoring: %m");
+
         server_space_usage_message(s, NULL);
         return 0;
 }
@@ -1253,20 +1258,14 @@ static int dispatch_sigrtmin1(sd_event_source *es, const struct signalfd_siginfo
         return 0;
 }
 
-
-static int dispatch_sigrtmin2(sd_event_source *es, const struct signalfd_siginfo *si, void *userdata) {
-        Server *s = userdata;
-        int r;
-
+static void relinquish_var(Server *s) {
         assert(s);
 
         if (s->storage == STORAGE_NONE)
-                return 0;
+                return;
 
         if (s->runtime_journal && !s->system_journal)
-                return 0;
-
-        log_debug("Received request to relinquish /var from PID " PID_FMT, si->ssi_pid);
+                return;
 
         (void) system_journal_open(s, false, true);
 
@@ -1277,6 +1276,23 @@ static int dispatch_sigrtmin2(sd_event_source *es, const struct signalfd_siginfo
         if (unlink("/run/systemd/journal/flushed") < 0 && errno != ENOENT)
                 log_warning_errno(errno, "Failed to unlink /run/systemd/journal/flushed, ignoring: %m")  ;
 
+        /* NOTE: We don't create our own state file here, because dispatch_sigrtmin2() has to do it anyway.
+         * But if this function is ever called from another place, the creation must be done here too. */
+
+        return;
+}
+
+static int dispatch_sigrtmin2(sd_event_source *es, const struct signalfd_siginfo *si, void *userdata) {
+        Server *s = userdata;
+        int r;
+
+        assert(s);
+        assert(si);
+
+        log_debug("Received request to relinquish /var from PID " PID_FMT, si->ssi_pid);
+
+        relinquish_var(s);
+
         r = write_timestamp_file_atomic("/run/systemd/journal/relinquished", now(CLOCK_MONOTONIC));
         if (r < 0)
                 log_warning_errno(r, "Failed to write /run/systemd/journal/relinquished, ignoring: %m");