--- dahdi-linux-complete-2.7.0.1+2.7.0.1/linux/drivers/dahdi/dahdi-base.c	2013-08-22 02:36:34.000000000 +0700
+++ dahdi-linux-complete/linux/drivers/dahdi/dahdi-base.c	2013-11-07 22:04:15.605488557 +0700
@@ -173,7 +173,7 @@
 static sumtype *conf_sums;
 static sumtype *conf_sums_prev;
 
-static struct dahdi_span *master;
+static struct dahdi_span *master = NULL;
 struct file_operations *dahdi_transcode_fops = NULL;
 
 
@@ -241,10 +241,13 @@
 static int dahdi_chan_ioctl(struct file *file, unsigned int cmd, unsigned long data);
 
 #if defined(CONFIG_DAHDI_MMX) || defined(ECHO_CAN_FP)
-#if (defined(CONFIG_X86) && !defined(CONFIG_X86_64)) || defined(CONFIG_I386)
+#if (defined(CONFIG_X86) || defined(CONFIG_X86_64))
+#include <linux/hardirq.h> /* in_atomic */
+#ifndef X86_CR0_TS
+# define X86_CR0_TS	0x00000008 /* Task Switched */
+#endif
 struct fpu_save_buf {
 	unsigned long cr0;
-	unsigned long fpu_buf[128];
 };
 
 static DEFINE_PER_CPU(struct fpu_save_buf, fpu_buf);
@@ -260,14 +263,18 @@
  * inside a spinlock. Otherwise the context might be restored to the
  * wrong process.
  *
- * Current implementation is x86/ia32-specific and will not even build on 
- * x86_64)
+ * This code is x86/x86_64-specific.
  * */
 static inline void dahdi_kernel_fpu_begin(void)
 {
 	struct fpu_save_buf *buf = &__get_cpu_var(fpu_buf);
-	__asm__ __volatile__ ("movl %%cr0,%0; clts" : "=r" (buf->cr0));
-	__asm__ __volatile__ ("fnsave %0" : "=m" (buf->fpu_buf));
+
+	buf->cr0 = 0; /* irq_ts_save */
+	if (in_atomic() && (read_cr0() & X86_CR0_TS)) {
+		clts();
+		buf->cr0 = 1;
+	} /* endof irq_ts_save */
+        kernel_fpu_begin();
 }
 
 /** dahdi_kernel_fpu_end() - restore floating point context
@@ -278,20 +285,16 @@
 static inline void dahdi_kernel_fpu_end(void)
 {
 	struct fpu_save_buf *buf = &__get_cpu_var(fpu_buf);
-	__asm__ __volatile__ ("frstor %0" : "=m" (buf->fpu_buf));
-	__asm__ __volatile__ ("movl %0,%%cr0" : : "r" (buf->cr0));
+	kernel_fpu_end();
+	if (buf->cr0)
+		stts();
 }
 
-#else /* We haven't fixed FP context saving/restoring yet */
-/* Very strange things can happen when the context is not properly
- * restored. OTOH, some people do report success with this. Hence we
- * so far just issue a warning */
-#warning CONFIG_DAHDI_MMX may behave randomly on this platform
-#define dahdi_kernel_fpu_begin kernel_fpu_begin
-#define dahdi_kernel_fpu_end   kernel_fpu_end
+#else
+#error CONFIG_DAHDI_MMX | ECHO_CAN_FP is x86/x86_64-specific.
 #endif
 
-#endif
+#endif /* defined(CONFIG_DAHDI_MMX) || defined(ECHO_CAN_FP) */
 
 struct dahdi_timer {
 	spinlock_t lock;
@@ -3835,31 +3838,28 @@
 
 static void __dahdi_find_master_span(void)
 {
-	struct dahdi_span *s;
+	struct dahdi_span *s, *old_master, *new_master = NULL;
 	unsigned long flags;
-	struct dahdi_span *old_master;
 
 	spin_lock_irqsave(&chan_lock, flags);
 	old_master = master;
-	list_for_each_entry(s, &span_list, spans_node) {
-		if (s->alarms && old_master)
+        /* Searching for the FIRST reliable sync source with reverse for. */
+	list_for_each_entry_reverse(s, &span_list, spans_node) {
+		if (!can_provide_timing(s) || s->alarms)
 			continue;
 		if (dahdi_is_digital_span(s) &&
-		    !test_bit(DAHDI_FLAGBIT_RUNNING, &s->flags) &&
-		    old_master)
+		    !test_bit(DAHDI_FLAGBIT_RUNNING, &s->flags))
 			continue;
-		if (!can_provide_timing(s))
-			continue;
-		if (master == s)
-			continue;
-
-		master = s;
-		break;
+		if ((0 == s->channels) && !new_master)	/* dummy is better than nothing (coretimer). */
+			new_master = s;
+		new_master = s;	/* But real span is better than dummy. */
 	}
+	master = new_master;
 	spin_unlock_irqrestore(&chan_lock, flags);
 
 	if ((debug & DEBUG_MAIN) && (old_master != master))
-		module_printk(KERN_NOTICE, "Master changed to %s\n", s->name);
+		module_printk(KERN_NOTICE, "Master changed to '%s'\n",
+			      master ? master->name : "no master (core timer)");
 }
 
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 20)
@@ -7437,7 +7437,6 @@
 {
 	int res;
 	int x;
-	struct dahdi_span *new_master, *s;
 	unsigned long flags;
 
 	if (!test_bit(DAHDI_FLAGBIT_REGISTERED, &span->flags)) {
@@ -7472,25 +7471,7 @@
 	for (x=0;x<span->channels;x++)
 		dahdi_chan_unreg(span->chans[x]);
 
-	new_master = master; /* FIXME: locking */
-	if (master == span)
-		new_master = NULL;
-
-	spin_lock_irqsave(&chan_lock, flags);
-	list_for_each_entry(s, &span_list, spans_node) {
-		if ((s == new_master) || !can_provide_timing(s))
-			continue;
-		new_master = s;
-		break;
-	}
-	spin_unlock_irqrestore(&chan_lock, flags);
-	if (master != new_master) {
-		if (debug & DEBUG_MAIN) {
-			module_printk(KERN_NOTICE, "%s: Span ('%s') is new master\n", __FUNCTION__,
-				      (new_master)? new_master->name: "no master");
-		}
-	}
-	master = new_master;
+        __dahdi_find_master_span();
 	return 0;
 }