If the CPU load measurements are being driven by an external clock, then the prototype for sched_process_cpuload() must be available in include/nuttx/arch.h

ChangeLog

@@ -7275,3 +7275,7 @@
 	* configs/sam4s-xplained-pro/Kconfig, nsh/defconfig, and src/sam_tc.c:
 	  The SAM4S Xplained Pro now uses the extended timer/counter features.
 	  From Bob Doiron (2014-4-30).
+	* include/nuttx/arch.h and sched/os_internal.h:  If the CPU load
+	  measurements are being driven by an external clock, then the prototype
+	  for sched_process_cpuload() must be available in include/nuttx/arch.h
+	  (2014-4-30).

configs/sam4s-xplained-pro/src/sam_tc.c

@@ -48,6 +48,7 @@
 #include <stdio.h>
 #include <fcntl.h>
 
+#include <nuttx/arch.h>
 #include <nuttx/timer.h>
 #include <nuttx/clock.h>
 #include <nuttx/kthread.h>

include/nuttx/arch.h

@@ -1029,6 +1029,28 @@ void up_cxxinitialize(void);
 
 void sched_process_timer(void);
 
+/************************************************************************
+ * Name: sched_process_cpuload
+ *
+ * Description:
+ *   Collect data that can be used for CPU load measurements.
+ *
+ * Inputs:
+ *   None
+ *
+ * Return Value:
+ *   None
+ *
+ * Assumptions/Limitations:
+ *   This function is called from a timer interrupt handler with all
+ *   interrupts disabled.
+ *
+ ************************************************************************/
+
+#if defined(CONFIG_SCHED_CPULOAD) && defined(CONFIG_SCHED_CPULOAD_EXTCLK)
+void weak_function sched_process_cpuload(void);
+#endif
+
 /****************************************************************************
  * Name: irq_dispatch
  *

sched/os_internal.h

@@ -255,7 +255,7 @@ int  sched_reprioritize(FAR struct tcb_s *tcb, int sched_priority);
 #else
 #  define sched_reprioritize(tcb,sched_priority) sched_setpriority(tcb,sched_priority)
 #endif
-#ifdef CONFIG_SCHED_CPULOAD
+#if defined(CONFIG_SCHED_CPULOAD) && !defined(CONFIG_SCHED_CPULOAD_EXTCLK)
 void weak_function sched_process_cpuload(void);
 #endif
 bool sched_verifytcb(FAR struct tcb_s *tcb);