调整代码，以支持cpu usage

libcpu/arm/cortex-a/interrupt.c

@@ -27,6 +27,20 @@ struct rt_irq_desc isr_table[MAX_HANDLERS];
 rt_uint32_t rt_interrupt_from_thread        = 0;
 rt_uint32_t rt_interrupt_to_thread          = 0;
 rt_uint32_t rt_thread_switch_interrupt_flag = 0;
+
+#ifdef RT_USING_HOOK
+static void (*rt_interrupt_switch_hook)(void);
+
+void rt_interrupt_switch_sethook(void (*hook)(void))
+{
+    rt_interrupt_switch_hook = hook;
+}
+#endif
+
+void rt_interrupt_hook(void)
+{
+    RT_OBJECT_HOOK_CALL(rt_interrupt_switch_hook, ());
+}
 #endif
 
 const unsigned int VECTOR_BASE = 0x00;

libcpu/arm/cortex-a/start_gcc.S

@@ -341,6 +341,8 @@ rt_hw_context_switch_interrupt_do:
     ldr     r6,  [r6]
     ldr     sp,  [r6]       @ get new task's stack pointer
 
+    bl rt_interrupt_hook
+
 #ifdef RT_USING_FPU
 /* fpu context */
     ldmfd sp!, {r6}