diff --git a/src/Kconfig b/src/Kconfig
index 70805264c5..22942a017e 100644
--- a/src/Kconfig
+++ b/src/Kconfig
@@ -20,7 +20,7 @@ config RT_USING_ARCH_DATA_TYPE
 config RT_USING_SMP
     bool "Enable SMP(Symmetric multiprocessing)"
     default n
-	help
+    help
         This option should be selected by machines which have an SMP-
         capable CPU.
         The only effect of this option is to make the SMP-related
@@ -28,10 +28,10 @@ config RT_USING_SMP
 
 config RT_CPUS_NR
     int "Number of CPUs"
-	default 2
-	depends on RT_USING_SMP
+    default 2
+    depends on RT_USING_SMP
     help
-		Number of CPUs in the system
+        Number of CPUs in the system
 
 config RT_ALIGN_SIZE
     int "Alignment size for CPU architecture data access"
diff --git a/src/cpu.c b/src/cpu.c
index f6f210eda8..96e585713b 100644
--- a/src/cpu.c
+++ b/src/cpu.c
@@ -7,9 +7,8 @@
  * Date           Author       Notes
  * 2018-10-30     Bernard      The first version
  */
-
-#include <rtthread.h>
 #include <rthw.h>
+#include <rtthread.h>
 
 #ifdef RT_USING_SMP
 static struct rt_cpu rt_cpus[RT_CPUS_NR];
@@ -20,24 +19,24 @@ rt_hw_spinlock_t _cpus_lock;
  */
 static void rt_preempt_disable(void)
 {
-	register rt_base_t level;
-	struct rt_thread *current_thread;
+    register rt_base_t level;
+    struct rt_thread *current_thread;
 
-	/* disable interrupt */
-	level = rt_hw_local_irq_disable();
+    /* disable interrupt */
+    level = rt_hw_local_irq_disable();
 
-	current_thread = rt_thread_self();
-	if (!current_thread)
-	{
-		rt_hw_local_irq_enable(level);
-		return;
-	}
+    current_thread = rt_thread_self();
+    if (!current_thread)
+    {
+        rt_hw_local_irq_enable(level);
+        return;
+    }
 
-	/* lock scheduler for local cpu */
-	current_thread->scheduler_lock_nest ++;
+    /* lock scheduler for local cpu */
+    current_thread->scheduler_lock_nest ++;
 
-	/* enable interrupt */
-	rt_hw_local_irq_enable(level);
+    /* enable interrupt */
+    rt_hw_local_irq_enable(level);
 }
 
 /*
@@ -45,66 +44,66 @@ static void rt_preempt_disable(void)
  */
 static void rt_preempt_enable(void)
 {
-	register rt_base_t level;
-	struct rt_thread *current_thread;
+    register rt_base_t level;
+    struct rt_thread *current_thread;
 
-	/* disable interrupt */
-	level = rt_hw_local_irq_disable();
+    /* disable interrupt */
+    level = rt_hw_local_irq_disable();
 
-	current_thread = rt_thread_self();
-	if (!current_thread)
-	{
-		rt_hw_local_irq_enable(level);
-		return;
-	}
+    current_thread = rt_thread_self();
+    if (!current_thread)
+    {
+        rt_hw_local_irq_enable(level);
+        return;
+    }
 
-	/* unlock scheduler for local cpu */
-	current_thread->scheduler_lock_nest --;
+    /* unlock scheduler for local cpu */
+    current_thread->scheduler_lock_nest --;
 
-	rt_schedule();
-	/* enable interrupt */
-	rt_hw_local_irq_enable(level);
+    rt_schedule();
+    /* enable interrupt */
+    rt_hw_local_irq_enable(level);
 }
 
 void rt_spin_lock_init(struct rt_spinlock *lock)
 {
-	rt_hw_spin_lock_init(&lock->lock);
+    rt_hw_spin_lock_init(&lock->lock);
 }
 RTM_EXPORT(rt_spin_lock_init)
 
 void rt_spin_lock(struct rt_spinlock *lock)
 {
-	rt_preempt_disable();
-	rt_hw_spin_lock(&lock->lock);
+    rt_preempt_disable();
+    rt_hw_spin_lock(&lock->lock);
 }
 RTM_EXPORT(rt_spin_lock)
 
 void rt_spin_unlock(struct rt_spinlock *lock)
 {
-	rt_hw_spin_unlock(&lock->lock);
-	rt_preempt_enable();
+    rt_hw_spin_unlock(&lock->lock);
+    rt_preempt_enable();
 }
 RTM_EXPORT(rt_spin_unlock)
 
 rt_base_t rt_spin_lock_irqsave(struct rt_spinlock *lock)
 {
-	unsigned long level;
+    unsigned long level;
 
-	rt_preempt_disable();
+    rt_preempt_disable();
 
-	level = rt_hw_local_irq_disable();
-	rt_hw_spin_lock(&lock->lock);
+    level = rt_hw_local_irq_disable();
+    rt_hw_spin_lock(&lock->lock);
 
-	return level;
+    return level;
 }
 RTM_EXPORT(rt_spin_lock_irqsave)
 
 void rt_spin_unlock_irqrestore(struct rt_spinlock *lock, rt_base_t level)
 {
-	rt_hw_spin_unlock(&lock->lock);
-	rt_hw_local_irq_enable(level);
+    rt_hw_spin_unlock(&lock->lock);
+    rt_hw_local_irq_enable(level);
 
-	rt_preempt_enable();
+    rt_preempt_enable();
 }
 RTM_EXPORT(rt_spin_unlock_irqrestore)
 
diff --git a/src/scheduler.c b/src/scheduler.c
index 0faafaa2fc..f671a49623 100644
--- a/src/scheduler.c
+++ b/src/scheduler.c
@@ -83,7 +83,7 @@ static void _rt_scheduler_stack_check(struct rt_thread *thread)
     RT_ASSERT(thread != RT_NULL);
 
 #if defined(ARCH_CPU_STACK_GROWS_UPWARD)
-	if (*((rt_uint8_t *)((rt_ubase_t)thread->stack_addr + thread->stack_size - 1)) != '#' ||
+    if (*((rt_uint8_t *)((rt_ubase_t)thread->stack_addr + thread->stack_size - 1)) != '#' ||
 #else
     if (*((rt_uint8_t *)thread->stack_addr) != '#' ||
 #endif
@@ -958,7 +958,7 @@ rt_uint16_t rt_critical_level(void)
 
     return current_thread->critical_lock_nest;
 #else
-	return rt_scheduler_lock_nest;
+    return rt_scheduler_lock_nest;
 #endif /*RT_USING_SMP*/
 }
 RTM_EXPORT(rt_critical_level);