diff --git a/AppKit/fifo.c b/AppKit/fifo.c
index b632666..a24e210 100644
--- a/AppKit/fifo.c
+++ b/AppKit/fifo.c
@@ -12,10 +12,7 @@ os_err_t fifo_put(fifo_t* self, uint8_t data){
 
     os_size_t write_idx = self->write_idx;
 
-    os_size_t next_write_idx = write_idx + 1;
-    if(next_write_idx >= self->buffer_size){
-        next_write_idx = 0;
-    }
+    os_size_t next_write_idx = fifo_next(self, self->write_idx);
 
     if(next_write_idx == self->read_idx){
         return OS_ERR_FULL;
@@ -38,10 +35,7 @@ os_err_t fifo_get(fifo_t* self, uint8_t* data){
         *data = self->buffer[read_idx];
     }
 
-    os_size_t next_read_idx = read_idx + 1;
-    if(next_read_idx >= self->buffer_size){
-        next_read_idx = 0;
-    }
+    os_size_t next_read_idx = fifo_next(self, self->read_idx);
     self->read_idx = next_read_idx;
     return OS_ERR_OK;
 }
diff --git a/AppKit/fifo.h b/AppKit/fifo.h
index 0794224..b1f32bc 100644
--- a/AppKit/fifo.h
+++ b/AppKit/fifo.h
@@ -22,11 +22,11 @@
 typedef struct fifo_t{
     uint8_t* buffer;
     os_size_t buffer_size;
-    os_size_t write_idx;
-    os_size_t read_idx;
+    volatile os_size_t write_idx;
+    volatile os_size_t read_idx;
 }fifo_t;
 
-#define FIFO_INVALID_POS ((os_size_t)(-1))
+#define FIFO_INVALID_POS ((os_size_t)(-1u))
 
 /* ==================================================================================================== */
 /* 接口 */
@@ -61,11 +61,17 @@ os_size_t fifo_capacity(fifo_t* self){
 }
 
 OS_STATIC_FORCE_INLINE
-os_bool_t fifo_is_full(fifo_t* self){
-    os_size_t next_write_idx = self->write_idx + 1;
-    if(next_write_idx>=self->buffer_size){
-        next_write_idx = 0;
+os_size_t fifo_next(fifo_t* self, os_size_t idx){
+    idx += 1;
+    if(idx >= self->buffer_size){
+        idx = 0;
     }
+    return idx;
+}
+
+OS_STATIC_FORCE_INLINE
+os_bool_t fifo_is_full(fifo_t* self){
+    os_size_t next_write_idx = fifo_next(self, self->write_idx);
     return (next_write_idx==self->read_idx)?OS_TRUE:OS_FALSE;
 }