daemon: Raise an error if 'max_workers' < 1 in libvirtd.conf

Hypervisor drivers (e.g. QEMU) assume that they run in a separate
thread from the main event loop thread otherwise deadlocks can
occur. Therefore let's report an error if max_workers < 1 is set in
the libvirtd configuration file.
Signed-off-by: NMarc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: NBoris Fiuczynski <fiuczy@linux.ibm.com>
Reviewed-by: NBjoern Walk <bwalk@linux.ibm.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>

src/remote/remote_daemon_config.c

@@ -337,6 +337,11 @@ daemonConfigLoadOptions(struct daemonConfig *data,
         goto error;
     if (virConfGetValueUInt(conf, "max_workers", &data->max_workers) < 0)
         goto error;
+    if (data->max_workers < 1) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("'max_workers' must be greater than 0"));
+        goto error;
+    }
     if (virConfGetValueUInt(conf, "max_clients", &data->max_clients) < 0)
         goto error;
     if (virConfGetValueUInt(conf, "max_queued_clients", &data->max_queued_clients) < 0)