--- a/configure.ac	Mon Oct 21 19:16:48 2013 +0200
+++ b/configure.ac	Mon Oct 21 19:27:50 2013 +0200
@@ -932,6 +932,35 @@
 fi
 
 #------------------------------------------------------------------------------
+# syslog output in realtime context
+#------------------------------------------------------------------------------
+
+AC_MSG_CHECKING([whether to syslog in realtime context])
+
+AC_ARG_ENABLE([rt-syslog],
+    AS_HELP_STRING([--enable-rt-syslog],
+                   [Enable RT syslog (default: yes)]),
+    [
+        case "${enableval}" in
+            yes) rtsyslog=1
+                ;;
+            no) rtsyslog=0
+                ;;
+            *) AC_MSG_ERROR([Invalid value for --enable-rt-syslog])
+                ;;
+        esac
+    ],
+    [rtsyslog=1]
+)
+
+if test "x${rtsyslog}" = "x1"; then
+    AC_DEFINE([EC_RT_SYSLOG], [1], [Output to syslog in RT context])
+    AC_MSG_RESULT([yes])
+else
+    AC_MSG_RESULT([no])
+fi
+
+#------------------------------------------------------------------------------
 
 AC_CONFIG_FILES([
         Doxyfile

--- a/master/domain.c	Mon Oct 21 19:16:48 2013 +0200
+++ b/master/domain.c	Mon Oct 21 19:27:50 2013 +0200
@@ -466,7 +466,10 @@
             ec_fmmu_config_t, list);
     unsigned int redundancy;
 #endif
-    unsigned int dev_idx, wc_change;
+    unsigned int dev_idx;
+#ifdef EC_RT_SYSLOG
+    unsigned int wc_change;
+#endif
 
 #if DEBUG_REDUNDANCY
     EC_MASTER_DBG(domain->master, 1, "domain %u process\n", domain->index);
@@ -569,6 +572,7 @@
 
     redundancy = redundant_wc > 0;
     if (redundancy != domain->redundancy_active) {
+#ifdef EC_RT_SYSLOG
         if (redundancy) {
             EC_MASTER_WARN(domain->master,
                     "Domain %u: Redundant link in use!\n",
@@ -578,23 +582,29 @@
                     "Domain %u: Redundant link unused again.\n",
                     domain->index);
         }
+#endif
         domain->redundancy_active = redundancy;
     }
 #else
     domain->redundancy_active = 0;
 #endif
 
+#ifdef EC_RT_SYSLOG
     wc_change = 0;
+#endif
     wc_total = 0;
     for (dev_idx = EC_DEVICE_MAIN;
             dev_idx < ec_master_num_devices(domain->master); dev_idx++) {
         if (wc_sum[dev_idx] != domain->working_counter[dev_idx]) {
+#ifdef EC_RT_SYSLOG
             wc_change = 1;
+#endif
             domain->working_counter[dev_idx] = wc_sum[dev_idx];
         }
         wc_total += wc_sum[dev_idx];
     }
 
+#ifdef EC_RT_SYSLOG
     if (wc_change) {
         domain->working_counter_changes++;
     }
@@ -630,6 +640,7 @@
 
         domain->working_counter_changes = 0;
     }
+#endif
 }
 
 /*****************************************************************************/

--- a/master/master.c	Mon Oct 21 19:16:48 2013 +0200
+++ b/master/master.c	Mon Oct 21 19:27:50 2013 +0200
@@ -852,9 +852,13 @@
                     > ext_injection_timeout_jiffies)
 #endif
             {
+#if defined EC_RT_SYSLOG || DEBUG_INJECT
                 unsigned int time_us;
+#endif
 
                 datagram->state = EC_DATAGRAM_ERROR;
+
+#if defined EC_RT_SYSLOG || DEBUG_INJECT
 #ifdef EC_HAVE_CYCLES
                 time_us = (unsigned int)
                     ((cycles_now - datagram->cycles_sent) * 1000LL)
@@ -867,6 +871,7 @@
                         " external datagram %s size=%zu,"
                         " max_queue_size=%zu\n", time_us, datagram->name,
                         datagram->data_size, master->max_queue_size);
+#endif
             }
             else {
 #if DEBUG_INJECT
@@ -944,8 +949,10 @@
     list_for_each_entry(queued_datagram, &master->datagram_queue, queue) {
         if (queued_datagram == datagram) {
             datagram->skip_count++;
+#ifdef EC_RT_SYSLOG
             EC_MASTER_DBG(master, 1,
                     "Datagram %p already queued (skipping).\n", datagram);
+#endif
             datagram->state = EC_DATAGRAM_QUEUED;
             return;
         }
@@ -1132,7 +1139,9 @@
             ec_print_data(frame_data, size);
         }
         master->stats.corrupted++;
+#ifdef EC_RT_SYSLOG
         ec_master_output_stats(master);
+#endif
         return;
     }
 
@@ -1151,7 +1160,9 @@
             ec_print_data(frame_data, size);
         }
         master->stats.corrupted++;
+#ifdef EC_RT_SYSLOG
         ec_master_output_stats(master);
+#endif
         return;
     }
 
@@ -1173,7 +1184,9 @@
                 ec_print_data(frame_data, size);
             }
             master->stats.corrupted++;
+#ifdef EC_RT_SYSLOG
             ec_master_output_stats(master);
+#endif
             return;
         }
 
@@ -1192,7 +1205,9 @@
         // no matching datagram was found
         if (!matched) {
             master->stats.unmatched++;
+#ifdef EC_RT_SYSLOG
             ec_master_output_stats(master);
+#endif
 
             if (unlikely(master->debug_level > 0)) {
                 EC_MASTER_DBG(master, 0, "UNMATCHED datagram:\n");
@@ -2485,6 +2500,8 @@
             list_del_init(&datagram->queue);
             datagram->state = EC_DATAGRAM_TIMED_OUT;
             master->stats.timeouts++;
+
+#ifdef EC_RT_SYSLOG
             ec_master_output_stats(master);
 
             if (unlikely(master->debug_level > 0)) {
@@ -2502,6 +2519,7 @@
                         " index %02X waited %u us.\n",
                         datagram, datagram->index, time_us);
             }
+#endif /* RT_SYSLOG */
         }
     }
 }