[PATCH] Cleanup & fix lost ticks handling on x86-64

This cleans up the x86-64 lost tick handling and fixes some issues:

First it moves that code into an own function.

The newer could would become very noisy when the machine loses timer ticks
regularly.  This happens often on some laptops etc.  during the acpi ec
access (nothing much can be really done about it) This patch prints the
warnings only once.

It also fixes the logic on when to ask cpufreq for a new estimate.

And it implements timer fallback to HPET when there are really lots of lost
ticks.  This is following i386.  PIT fallback isn't implemented right now
though, but I hope we don't need this.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/x86_64/kernel/time.c

@@ -309,6 +309,43 @@ unsigned long long monotonic_clock(void)
 }
 EXPORT_SYMBOL(monotonic_clock);
 
+static noinline void handle_lost_ticks(int lost, struct pt_regs *regs)
+{
+    static long lost_count;
+    static int warned;
+
+    if (report_lost_ticks) {
+	    printk(KERN_WARNING "time.c: Lost %d timer "
+		   "tick(s)! ", lost);
+	    print_symbol("rip %s)\n", regs->rip);
+    }
+
+    if (lost_count == 100 && !warned) {
+	    printk(KERN_WARNING
+		   "warning: many lost ticks.\n"
+		   KERN_WARNING "Your time source seems to be instable or "
+		   		"some driver is hogging interupts\n");
+	    print_symbol("rip %s\n", regs->rip);
+	    if (vxtime.mode == VXTIME_TSC && vxtime.hpet_address) {
+		    printk(KERN_WARNING "Falling back to HPET\n");
+		    vxtime.last = hpet_readl(HPET_T0_CMP) - hpet_tick;
+		    vxtime.mode = VXTIME_HPET;
+		    do_gettimeoffset = do_gettimeoffset_hpet;
+	    }
+	    /* else should fall back to PIT, but code missing. */
+	    warned = 1;
+    } else
+	    lost_count++;
+
+#ifdef CONFIG_CPU_FREQ
+    /* In some cases the CPU can change frequency without us noticing
+       (like going into thermal throttle)
+       Give cpufreq a change to catch up. */
+    if ((lost_count+1) % 25 == 0) {
+	    cpufreq_delayed_get();
+    }
+#endif
+}
 
 static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 {
@@ -371,28 +408,7 @@ static irqreturn_t timer_interrupt(int irq, void *dev_id, struct pt_regs *regs)
 	}
 
 	if (lost > 0) {
-		static long lost_count;
-
-		if (report_lost_ticks) {
-			printk(KERN_WARNING "time.c: Lost %d timer "
-			       "tick(s)! ", lost);
-			print_symbol("rip %s)\n", regs->rip);
-		}
-
-		if (lost_count == 100) {
-			printk(KERN_WARNING
-   "warning: many lost ticks.\n"
-   KERN_WARNING "Your time source seems to be instable or some driver is hogging interupts\n");
-			print_symbol("rip %s\n", regs->rip);
-			lost_count = 0;
-		} else
-			lost_count++;
-
-		if ((lost_count % 25) == 0) {
-#ifdef CONFIG_CPU_FREQ
-			cpufreq_delayed_get();
-#endif
-		}
+		handle_lost_ticks(lost, regs);
 		jiffies += lost;
 	}
 
@@ -563,9 +579,13 @@ static void handle_cpufreq_delayed_get(void *v)
  */
 static void cpufreq_delayed_get(void)
 {
+	static int warned;
 	if (cpufreq_init && !cpufreq_delayed_issched) {
 		cpufreq_delayed_issched = 1;
+		if (!warned) {
+			warned = 1;
 			printk(KERN_DEBUG "Losing some ticks... checking if CPU frequency changed.\n");
+		}
 		schedule_work(&cpufreq_delayed_get_work);
 	}
 }