Index: dahdi-base.c
===================================================================
--- dahdi-base.c	(revision 4909)
+++ dahdi-base.c	(working copy)
@@ -230,7 +230,8 @@
 static sumtype *conf_sums;
 static sumtype *conf_sums_prev;
 
-static struct dahdi_span *master;
+static struct dahdi_span *master = NULL;
+static struct dahdi_span *pref_master = NULL;
 static struct file_operations dahdi_fops;
 struct file_operations *dahdi_transcode_fops = NULL;
 
@@ -3221,6 +3222,47 @@
 	spin_unlock_irqrestore(&chan->lock, flags);
 }
 
+static inline int __can_be_master (struct dahdi_span *span) {
+	if (span && !span->alarms && (span->flags & DAHDI_FLAG_RUNNING)) 
+		return 1;
+	return 0;
+}
+
+/*
+  pavel[AT]parabel.ru
+  1. trying preffered master SPAN
+  2. trying non-zero channel SPANS
+  3. trying zero-channel SPANS (dahdi_dummy,...)
+*/
+static void dahdi_checkmaster (void) {
+	struct dahdi_span *dummy = NULL;
+	struct dahdi_span *newmaster = NULL;
+	struct dahdi_span *curmaster = master;
+	int x;
+
+	if (__can_be_master(pref_master)) {
+		newmaster = pref_master;
+	} else {
+		/* Switch to other master if current master in alarm */
+		for (x=1; x<maxspans; x++) {
+			if (__can_be_master(spans[x])) {
+				if (spans[x]->channels > 0) {
+					newmaster = spans[x];
+					break; //We're happy now.
+				} else {
+					if (!dummy) 
+						dummy = spans[x];
+				}
+
+			}
+		}
+	}
+
+	master = (newmaster) ? newmaster : dummy;
+	if (master != curmaster)
+		module_printk(KERN_INFO, "Master changed to %s\n", (master)? master->name: "no master");
+}
+
 void dahdi_alarm_notify(struct dahdi_span *span)
 {
 	int x;
@@ -3237,16 +3279,8 @@
 		span->lastalarms = span->alarms;
 		for (x = 0; x < span->channels; x++)
 			dahdi_alarm_channel(span->chans[x], span->alarms);
-		/* Switch to other master if current master in alarm */
-		for (x=1; x<maxspans; x++) {
-			if (spans[x] && !spans[x]->alarms && (spans[x]->flags & DAHDI_FLAG_RUNNING)) {
-				if(master != spans[x])
-					module_printk(KERN_NOTICE, "Master changed to %s\n", spans[x]->name);
-				master = spans[x];
-				break;
-			}
-		}
 	}
+	dahdi_checkmaster ();
 }
 
 #define VALID_SPAN(j) do { \
@@ -3729,6 +3763,7 @@
 				spin_unlock_irqrestore(&spans[j]->chans[x]->lock, flags);
 				spans[j]->chans[x]->rxhooksig = DAHDI_RXSIG_INITIAL;
 			}
+			dahdi_checkmaster ();
 		}
 		return 0;
 	case DAHDI_SHUTDOWN:
@@ -5374,14 +5409,10 @@
 				"%d channels\n", span->spanno, span->name, span->channels);
 	}
 
-	if (!master || prefmaster) {
-		master = span;
-		if (debug) {
-			module_printk(KERN_NOTICE, "Span ('%s') is new master\n", 
-					span->name);
-		}
-	}
 
+	if (prefmaster)
+		pref_master = span;
+
 	return 0;
 }
 
@@ -5389,7 +5420,6 @@
 {
 	int x;
 	int new_maxspans;
-	static struct dahdi_span *new_master;
 
 #ifdef CONFIG_PROC_FS
 	char tempfile[17];
@@ -5426,23 +5456,17 @@
 	for (x=0;x<span->channels;x++)
 		dahdi_chan_unreg(span->chans[x]);
 	new_maxspans = 0;
-	new_master = master; /* FIXME: locking */
 	if (master == span)
-		new_master = NULL;
+		master = NULL;
+	if (pref_master == span)
+		pref_master = NULL;
 	for (x=1;x<DAHDI_MAX_SPANS;x++) {
 		if (spans[x]) {
 			new_maxspans = x+1;
-			if (!new_master)
-				new_master = spans[x];
 		}
 	}
 	maxspans = new_maxspans;
-	if (master != new_master)
-		if (debug)
-			module_printk(KERN_NOTICE, "%s: Span ('%s') is new master\n", __FUNCTION__,
-				      (new_master)? new_master->name: "no master");
-	master = new_master;
-
+	dahdi_checkmaster ();
 	return 0;
 }