diff --git a/src/gausskernel/cbb/bbox/bbox_lib.cpp b/src/gausskernel/cbb/bbox/bbox_lib.cpp
index 62873f7f6..41f522373 100644
--- a/src/gausskernel/cbb/bbox/bbox_lib.cpp
+++ b/src/gausskernel/cbb/bbox/bbox_lib.cpp
@@ -245,9 +245,6 @@ char* bbox_strstr(const char* s1, const char* s2)
     return NULL;
 }
 
-/*
- * make a directory
- */
 /*
 function name: bbox_mkdir
 description: We distinguish parent directory and child directory through character '/',
@@ -304,8 +301,16 @@ s32 bbox_mkdir(const char* pszDir)
 }
 
 /*
- * search free pipe id
- */
+function name: bbox_GetFreePid
+description: Through a for loop, we search a free pipe in a structure array, to an array element if its 
+					member variable isUsed's value is 0, we return the array element's another member variable
+                    stPid's address.
+arguments: void
+return value: An pointer of type struct PIPE_ID* or NULL.
+note: none
+date: 2022/8/2
+contact tel: same
+*/
 struct PIPE_ID* bbox_GetFreePid(void)
 {
     u32 i;