diff --git a/ChangeLog.md b/ChangeLog.md
index b7360119..4f50fc32 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,7 @@
+## [2.5.2] - 2022-06-28
+### Changed
+- modify the global lock to protect the at agent.
+
 ## [2.5.1] - 2022-06-02
 ### Added
 - add dynamic create and destroy api for task, sem, mutex, event, timer and corresponding unit test case.
diff --git a/devices/ec20_200_600/ec600s.c b/devices/ec20_200_600/ec600s.c
index 4b135183..e3109338 100644
--- a/devices/ec20_200_600/ec600s.c
+++ b/devices/ec20_200_600/ec600s.c
@@ -42,7 +42,7 @@ static int ec600s_check_ready(void)
 {
     at_echo_t echo;
     int try = 0;
-    
+
     while (try++ < 10) {
         tos_at_echo_create(&echo, NULL, 0, NULL);
         tos_at_cmd_exec(AT_AGENT, &echo, 1000, "AT\r\n");
@@ -60,7 +60,7 @@ static int ec600s_echo_close(void)
     int try = 0;
 
     tos_at_echo_create(&echo, NULL, 0, NULL);
-    
+
     while (try++ < 10) {
         tos_at_cmd_exec(AT_AGENT, &echo, 1000, "ATE0\r\n");
         if (echo.status == AT_ECHO_STATUS_OK) {
@@ -75,7 +75,7 @@ static int ec600s_sim_card_check(void)
     at_echo_t echo;
     int try = 0;
     char echo_buffer[32];
-	
+
     tos_at_echo_create(&echo, echo_buffer, sizeof(echo_buffer), NULL);
     while (try++ < 10) {
         tos_at_cmd_exec(AT_AGENT, &echo, 1000, "AT+CPIN?\r\n");
@@ -84,7 +84,7 @@ static int ec600s_sim_card_check(void)
         }
         tos_sleep_ms(2000);
     }
-    
+
     return -1;
 }
 
@@ -94,7 +94,7 @@ static int ec600s_signal_quality_check(void)
     at_echo_t echo;
     char echo_buffer[32], *str;
     int try = 0;
-	
+
     tos_at_echo_create(&echo, echo_buffer, sizeof(echo_buffer), NULL);
     while (try++ < 10) {
         tos_at_cmd_exec(AT_AGENT, &echo, 1000, "AT+CSQ\r\n");
@@ -106,7 +106,7 @@ static int ec600s_signal_quality_check(void)
         if (!str) {
             return -1;
         }
-        
+
         sscanf(str, "+CSQ:%d,%d", &rssi, &ber);
         if (rssi != 99) {
             return 0;
@@ -122,7 +122,7 @@ static int ec600s_gsm_network_check(void)
     at_echo_t echo;
     char echo_buffer[32], *str;
     int try = 0;
-	
+
     tos_at_echo_create(&echo, echo_buffer, sizeof(echo_buffer), NULL);
     while (try++ < 10) {
         tos_at_cmd_exec(AT_AGENT, &echo, 1000, "AT+CREG?\r\n");
@@ -140,8 +140,8 @@ static int ec600s_gsm_network_check(void)
         }
         tos_sleep_ms(2000);
     }
-    
-    return -1;	
+
+    return -1;
 }
 
 static int ec600s_gprs_network_check(void)
@@ -168,7 +168,7 @@ static int ec600s_gprs_network_check(void)
         }
         tos_sleep_ms(2000);
     }
-		
+
     return -1;
 }
 
@@ -181,7 +181,7 @@ static int ec600s_close_apn(void)
     if (echo.status == AT_ECHO_STATUS_OK) {
         return 0;
     }
-   
+
     return -1;
 }
 
@@ -206,17 +206,17 @@ static int ec600s_set_apn(void)
 static int ec600s_init(void)
 {
     printf("Init ec600s ...\n" );
-    
+
     if (ec600s_check_ready() != 0) {
         printf("wait module ready timeout, please check your module\n");
         return -1;
     }
-    
+
     if (ec600s_echo_close() != 0) {
         printf("echo close failed,please check your module\n");
         return -1;
     }
-		
+
     if(ec600s_sim_card_check() != 0) {
         printf("sim card check failed,please insert your card\n");
         return -1;
@@ -226,22 +226,22 @@ static int ec600s_init(void)
         printf("signal quality check status failed\n");
         return -1;
     }
-		
+
     if(ec600s_gsm_network_check() != 0) {
         printf("GSM network register status check fail\n");
         return -1;
     }
-    
+
     if(ec600s_gprs_network_check() != 0) {
         printf("GPRS network register status check fail\n");
         return -1;
     }
-    
+
     if(ec600s_close_apn() != 0) {
         printf("close apn failed\n");
         return -1;
     }
-		
+
     if (ec600s_set_apn() != 0) {
         printf("apn set FAILED\n");
         return -1;
@@ -259,14 +259,14 @@ static int ec600s_connect_establish(int id, sal_proto_t proto)
     char *query_result_str = NULL;
     char *remote_ip = NULL;
     char *remote_port = NULL;
-    
+
     tos_at_echo_create(&echo, echo_buffer, sizeof(echo_buffer), NULL);
     tos_at_cmd_exec(AT_AGENT, &echo, 1000, "AT+QISTATE=1,%d\r\n", id);
     if (echo.status != AT_ECHO_STATUS_OK) {
         printf("query socket %d state fail\r\n", id);
         return -1;
     }
-    
+
     sprintf(except_str, "+QISTATE: %d", id);
     query_result_str = strstr(echo_buffer, except_str);
     if (query_result_str) {
@@ -277,13 +277,13 @@ static int ec600s_connect_establish(int id, sal_proto_t proto)
 
     memset(except_str, 0, sizeof(except_str));
     sprintf(except_str, "+QIOPEN: %d,0", id);
-    
+
     remote_ip = (char*)tos_at_channel_ip_get(AT_AGENT, id);
     remote_port = (char*)tos_at_channel_port_get(AT_AGENT, id);
     if (!remote_ip || !remote_port) {
         return -2;
     }
-    
+
     tos_at_echo_create(&echo, NULL, 0, except_str);
     tos_at_cmd_exec_until(AT_AGENT, &echo, 4000, "AT+QIOPEN=1,%d,\"%s\",\"%s\",%d,0,1\r\n",
                         id, proto == TOS_SAL_PROTO_UDP ? "UDP" : "TCP", remote_ip, atoi(remote_port));
@@ -291,32 +291,32 @@ static int ec600s_connect_establish(int id, sal_proto_t proto)
         printf("establish socket %d on module fail\r\n", id);
         return -3;
     }
-    
+
     return 0;
 }
 
 static int ec600s_connect(const char *ip, const char *port, sal_proto_t proto)
 {
     int id;
-    
+
     id = tos_at_channel_alloc(AT_AGENT, ip, port);
     if (id == -1) {
         printf("at channel alloc fail\r\n");
         return -1;
     }
-    
+
     if (ec600s_connect_establish(id, proto) < 0) {
         tos_at_channel_free(AT_AGENT, id);
         return -2;
     }
-    
+
     return id;
 }
 
 static int ec600s_connect_with_size(const char *ip, const char *port, sal_proto_t proto, size_t socket_buffer_size)
 {
     int id;
-    
+
     id = tos_at_channel_alloc_with_size(AT_AGENT, ip, port, socket_buffer_size);
     if (id == -1) {
         printf("at channel alloc fail\r\n");
@@ -327,7 +327,7 @@ static int ec600s_connect_with_size(const char *ip, const char *port, sal_proto_
         tos_at_channel_free(AT_AGENT, id);
         return -2;
     }
-    
+
     return id;
 }
 
@@ -348,29 +348,21 @@ int ec600s_send(int id, const void *buf, size_t len)
     if (!tos_at_channel_is_working(AT_AGENT, id)) {
         return -1;
     }
-	
-    if (tos_at_global_lock_pend(AT_AGENT) != 0) {
-        return -1;
-    }
 
     tos_at_echo_create(&echo, NULL, 0, ">");
 
     tos_at_cmd_exec_until(AT_AGENT, &echo, 1000, "AT+QISEND=%d,%d\r\n", id, len);
 
     if (echo.status != AT_ECHO_STATUS_EXPECT) {
-        tos_at_global_lock_post(AT_AGENT);
         return -1;
     }
 
     tos_at_echo_create(&echo, NULL, 0, "SEND OK");
     tos_at_raw_data_send_until(AT_AGENT, &echo, 10000, (uint8_t *)buf, len);
     if (echo.status != AT_ECHO_STATUS_EXPECT) {
-        tos_at_global_lock_post(AT_AGENT);
         return -1;
     }
 
-    tos_at_global_lock_post(AT_AGENT);
-
     return len;
 }
 
@@ -388,34 +380,26 @@ int ec600s_sendto(int id, char *ip, char *port, const void *buf, size_t len)
 {
     at_echo_t echo;
 
-    if (tos_at_global_lock_pend(AT_AGENT) != 0) {
-        return -1;
-    }
-
     tos_at_echo_create(&echo, NULL, 0, ">");
     tos_at_cmd_exec_until(AT_AGENT, &echo, 1000, "AT+QISEND=%d,%d\r\n", id, len);
 
     if (echo.status != AT_ECHO_STATUS_EXPECT) {
-        tos_at_global_lock_post(AT_AGENT);
         return -1;
     }
 
     tos_at_echo_create(&echo, NULL, 0, "SEND OK");
     tos_at_raw_data_send(AT_AGENT, &echo, 1000, (uint8_t *)buf, len);
     if (echo.status != AT_ECHO_STATUS_EXPECT) {
-        tos_at_global_lock_post(AT_AGENT);
         return -1;
     }
 
-    tos_at_global_lock_post(AT_AGENT);
-
     return len;
 }
 
 static void ec600s_transparent_mode_exit(void)
 {
     at_echo_t echo;
-    
+
     tos_at_echo_create(&echo, NULL, 0, NULL);
     tos_at_cmd_exec(AT_AGENT, &echo, 500, "+++");
 }
@@ -423,7 +407,7 @@ static void ec600s_transparent_mode_exit(void)
 static int ec600s_close(int id)
 {
     at_echo_t echo;
-    
+
     ec600s_transparent_mode_exit();
 
     tos_at_echo_create(&echo, NULL, 0, NULL);
@@ -467,7 +451,7 @@ __STATIC__ void ec600s_incoming_data_process(void)
 		+QIURC: "recv",<sockid>,<datalen>
 		<data content>
     */
-	
+
     while (1) {
         if (tos_at_uart_read(AT_AGENT, &data, 1) != 1) {
             return;
@@ -492,7 +476,7 @@ __STATIC__ void ec600s_incoming_data_process(void)
     if (tos_at_uart_read(AT_AGENT, &data, 1) != 1) {
         return;
     }
-		
+
     do {
 #if !defined(MIN)
 #define MIN(a, b)   ((a) < (b) ? (a) : (b))
@@ -529,7 +513,7 @@ __STATIC__ void ec600s_domain_data_process(void)
     if (data == '0') {
         return;
     }
-    
+
     if (data == '\"') {
         /* start parser domain */
         while (1) {
@@ -595,7 +579,7 @@ sal_module_t sal_module_ec600s = {
 
 int ec600s_sal_init(hal_uart_port_t uart_port)
 {
-    
+
     if (tos_at_init(AT_AGENT, "ec600s_at", ec600s_at_parse_task_stk,
                     uart_port, ec600s_at_event,
                         sizeof(ec600s_at_event) / sizeof(ec600s_at_event[0])) != 0) {
@@ -608,7 +592,7 @@ int ec600s_sal_init(hal_uart_port_t uart_port)
     if (tos_sal_module_init() != 0) {
         return -1;
     }
-		
+
     return 0;
 }
 
@@ -623,7 +607,7 @@ int ec600s_sal_deinit()
     tos_sal_module_register_default();
 
     tos_at_deinit(AT_AGENT);
-    
+
     return 0;
 }
 
diff --git a/devices/esp8266/esp8266.c b/devices/esp8266/esp8266.c
index 13c340e6..5ba6094c 100644
--- a/devices/esp8266/esp8266.c
+++ b/devices/esp8266/esp8266.c
@@ -105,12 +105,15 @@ int esp8266_join_ap(const char *ssid, const char *pwd)
 {
     int try = 0;
     at_echo_t echo;
+    char echo_buffer[128];
 
-    tos_at_echo_create(&echo, NULL, 0, NULL);
+    tos_at_echo_create(&echo, echo_buffer, sizeof(echo_buffer), NULL);
     while (try++ < 10) {
-        tos_at_cmd_exec(AT_AGENT, &echo, 15000, "AT+CWJAP=\"%s\",\"%s\"\r\n", ssid, pwd);
+        tos_at_cmd_exec(AT_AGENT, &echo, 20000, "AT+CWJAP=\"%s\",\"%s\"\r\n", ssid, pwd);
         if (echo.status == AT_ECHO_STATUS_OK) {
-            return 0;
+            if (strstr(echo_buffer, "WIFI GOT IP")) {
+                return 0;
+            }
         }
     }
     return -1;
@@ -200,10 +203,6 @@ static int esp8266_send(int id, const void *buf, size_t len)
         return -1;
     }
 
-    if (tos_at_global_lock_pend(AT_AGENT) != 0) {
-        return -1;
-    }
-
     tos_at_echo_create(&echo, echo_buffer, sizeof(echo_buffer), ">");
 #if TOS_CFG_MODULE_SINGLE_LINK_EN > 0u
     tos_at_cmd_exec_until(&echo, 5000,
@@ -218,7 +217,6 @@ static int esp8266_send(int id, const void *buf, size_t len)
             tos_at_channel_set_broken(AT_AGENT, id);
         }
 
-        tos_at_global_lock_post(AT_AGENT);
         return -1;
     }
 
@@ -234,11 +232,9 @@ static int esp8266_send(int id, const void *buf, size_t len)
             tos_at_channel_set_broken(AT_AGENT, id);
         }
 
-        tos_at_global_lock_post(AT_AGENT);
         return -1;
     }
 
-    tos_at_global_lock_post(AT_AGENT);
     return len;
 }
 
@@ -251,10 +247,6 @@ static int esp8266_sendto(int id, char *ip, char *port, const void *buf, size_t
         return -1;
     }
 
-    if (tos_at_global_lock_pend(AT_AGENT) != 0) {
-        return -1;
-    }
-
     tos_at_echo_create(&echo, echo_buffer, sizeof(echo_buffer), ">");
 
     if (ip && port) {
@@ -280,7 +272,6 @@ static int esp8266_sendto(int id, char *ip, char *port, const void *buf, size_t
             tos_at_channel_set_broken(AT_AGENT, id);
         }
 
-        tos_at_global_lock_post(AT_AGENT);
         return -1;
     }
 
@@ -296,11 +287,9 @@ static int esp8266_sendto(int id, char *ip, char *port, const void *buf, size_t
             tos_at_channel_set_broken(AT_AGENT, id);
         }
 
-        tos_at_global_lock_post(AT_AGENT);
         return -1;
     }
 
-    tos_at_global_lock_post(AT_AGENT);
     return len;
 }
 
@@ -317,9 +306,9 @@ static int esp8266_recvfrom(int id, void *buf, size_t len)
 static int esp8266_close(int id)
 {
     at_echo_t echo;
-    
+
     tos_at_echo_create(&echo, NULL, 0, NULL);
-    
+
 #if TOS_CFG_MODULE_SINGLE_LINK_EN > 0u
     tos_at_cmd_exec(AT_AGENT, &echo, 1000, "AT+CIPCLOSE\r\n");
 #else
@@ -441,7 +430,7 @@ __STATIC__ void esp8266_incoming_data_process(void)
         if (tos_at_uart_read(AT_AGENT, buffer, read_len) != read_len) {
             return;
         }
-        
+
         //delay has two reason, wait for the data to be cached and untrigger scheduling
         tos_stopwatch_delay(200);
 
@@ -501,7 +490,7 @@ int esp8266_sal_deinit()
     tos_sal_module_register_default();
 
     tos_at_deinit(AT_AGENT);
-    
+
     return 0;
 }
 
diff --git a/kernel/core/include/tos_version.h b/kernel/core/include/tos_version.h
index 81c127bc..88e55ada 100644
--- a/kernel/core/include/tos_version.h
+++ b/kernel/core/include/tos_version.h
@@ -25,8 +25,8 @@
 
 #define TOS_VERSION_MAJOR   0x02
 #define TOS_VERSION_MINOR   0x05
-#define TOS_VERSION_PATCH   0x01
-#define TOS_VERSION "2.5.1"
+#define TOS_VERSION_PATCH   0x02
+#define TOS_VERSION "2.5.2"
 
 #endif /* _TOS_VERSION_H_ */
 
diff --git a/net/at/include/tos_at.h b/net/at/include/tos_at.h
index f3c3f3b1..70a74fab 100644
--- a/net/at/include/tos_at.h
+++ b/net/at/include/tos_at.h
@@ -140,22 +140,26 @@ typedef struct at_agent_st {
     k_task_t        parser;
     at_cache_t      recv_cache;
 
+    /* protected the AT agent, so only one AT instruction is executing any one time. */
     k_mutex_t       global_lock;
 
     char           *cmd_buf;
-    k_mutex_t       cmd_buf_lock;
+
+    /* global_lock has protected the at agent, so cmd buf lock is unnecessary,
+        the code will be removed in next version. */
+    // k_mutex_t       cmd_buf_lock;
 
     hal_uart_t      uart;
     k_mutex_t       uart_tx_lock;
 //    k_mutex_t       uart_rx_lock;
-    
+
 #if AT_INPUT_TYPE_FRAME_EN
     k_mail_q_t      uart_rx_frame_mail;
     uint8_t        *uart_rx_frame_mail_buffer;
     uint16_t        fifo_available_len;
 #else
     k_sem_t         uart_rx_sem;
-    
+
 #if AT_INPUT_SIMULATE_IDLE_EN
     k_timer_t       idle_check_timer;
 #endif  /* AT_INPUT_SIMULATE_IDLE_EN */
@@ -329,7 +333,7 @@ __API__ int tos_at_init(at_agent_t *at_agent, char *task_name, k_stack_t *stk, h
  * @brief De-initialize the at framework.
  *
  * @param[in]   at_agent    pointer to the at agent struct.
- * 
+ *
  * @attention None
  *
  * @return
diff --git a/net/at/src/tos_at.c b/net/at/src/tos_at.c
index 0e4e19e6..924d7a62 100644
--- a/net/at/src/tos_at.c
+++ b/net/at/src/tos_at.c
@@ -14,7 +14,7 @@
  * as the other licenses applicable to the third-party components included
  * within TencentOS.
  *---------------------------------------------------------------------------*/
- 
+
 /*
 Note:
     If you find that the AT framework occasionally loses characters,
@@ -46,11 +46,11 @@ __STATIC__ int at_uart_getchar_from_fifo(at_agent_t *at_agent, uint8_t *data)
 {
     TOS_CPU_CPSR_ALLOC();
     k_err_t err;
-    
+
     TOS_CPU_INT_DISABLE();
     err = tos_chr_fifo_pop(&at_agent->uart_rx_fifo, data);
     TOS_CPU_INT_ENABLE();
-    
+
     return err;
 }
 
@@ -79,30 +79,30 @@ __STATIC__ int at_uart_getchar(at_agent_t *at_agent, uint8_t *data, k_tick_t tim
             return -1;
         }
     }
-    
+
     if (at_uart_getchar_from_fifo(at_agent, data) != K_ERR_NONE) {
         return -1;
     }
-    
+
     return 0;
-    
+
 #else
     tos_stopwatch_delay(1);
 
     if (tos_sem_pend(&at_agent->uart_rx_sem, timeout) != K_ERR_NONE) {
         return -1;
     }
-    
+
     /*
         the uart_rx_fifo is only read by at_parser task,
         and it will be written in usart interrupt handler,
         so it is more effective to use critical sections.
     */
-    
+
 //    if (tos_mutex_pend(&at_agent->uart_rx_lock) != K_ERR_NONE) {
 //        return -1;
 //    }
-    
+
     if (at_uart_getchar_from_fifo(at_agent, data) != K_ERR_NONE) {
         return -1;
     }
@@ -274,7 +274,7 @@ __STATIC__ at_parse_status_t at_uart_line_parse(at_agent_t *at_agent)
             recv_cache->buffer[recv_cache->buffer_size - 1] = '\0';
             return AT_PARSE_STATUS_OVERFLOW;
         }
-        
+
         if (at_get_event(at_agent) != K_NULL) {
             return AT_PARSE_STATUS_EVENT;
         }
@@ -282,9 +282,9 @@ __STATIC__ at_parse_status_t at_uart_line_parse(at_agent_t *at_agent)
         if (at_is_echo_expect(at_agent)) {
             return AT_PARSE_STATUS_EXPECT;
         }
-        
+
         AT_LOG("recv_cache:[%s](%d)\r\n", recv_cache->buffer, recv_cache->recv_len);
-        
+
         if (strstr((char*)recv_cache->buffer, "OK")) {
             return AT_PARSE_STATUS_OK;
         } else if (strstr((char*)recv_cache->buffer, "FAIL")) {
@@ -344,11 +344,11 @@ __STATIC__ void at_parser(void *arg)
     recv_cache = &at_agent->recv_cache;
 
     while (K_TRUE) {
-        
+
         at_parse_status = at_uart_line_parse(at_agent);
-        
+
         AT_LOG("at line parser end!(%d)\r\n", at_parse_status);
-        
+
         tos_kprintln("--->%s", recv_cache->buffer);
 
         if (at_parse_status == AT_PARSE_STATUS_OVERFLOW) {
@@ -368,7 +368,7 @@ __STATIC__ void at_parser(void *arg)
         if (!at_echo) {
             continue;
         }
-        
+
         if (at_echo->buffer) {
             at_echo_buffer_copy(recv_cache, at_echo);
         }
@@ -467,16 +467,24 @@ __API__ int tos_at_raw_data_send(at_agent_t *at_agent, at_echo_t *echo, uint32_t
 {
     int ret = 0;
 
-    if (echo) {
-        at_echo_attach(at_agent, echo);
+    if (!echo) {
+        return -1;
     }
 
+    if (tos_at_global_lock_pend(at_agent) != 0) {
+        return -1;
+    }
+
+    at_echo_attach(at_agent, echo);
+
     ret = at_uart_send(at_agent, buf, size, 0xFFFF);
 
     tos_task_delay(tos_millisec2tick(timeout));
 
     at_agent->echo = K_NULL;
 
+    tos_at_global_lock_post(at_agent);
+
     return ret;
 }
 
@@ -488,7 +496,12 @@ __API__ int tos_at_raw_data_send_until(at_agent_t *at_agent, at_echo_t *echo, ui
         return -1;
     }
 
+    if (tos_at_global_lock_pend(at_agent) != 0) {
+        return -1;
+    }
+
     if (tos_sem_create(&echo->__expect_notify, 0) != K_ERR_NONE) {
+        tos_at_global_lock_post(at_agent);
         return -1;
     }
     echo->__is_expecting = K_TRUE;
@@ -504,6 +517,8 @@ __API__ int tos_at_raw_data_send_until(at_agent_t *at_agent, at_echo_t *echo, ui
 
     at_agent->echo = K_NULL;
 
+    tos_at_global_lock_post(at_agent);
+
     return ret;
 }
 
@@ -511,9 +526,9 @@ __STATIC__ int at_cmd_do_exec(at_agent_t *at_agent, const char *format, va_list
 {
     size_t cmd_len = 0;
 
-    if (tos_mutex_pend(&at_agent->cmd_buf_lock) != K_ERR_NONE) {
-        return -1;
-    }
+    // if (tos_mutex_pend(&at_agent->cmd_buf_lock) != K_ERR_NONE) {
+    //     return -1;
+    // }
 
     cmd_len = vsnprintf(at_agent->cmd_buf, AT_CMD_BUFFER_SIZE, format, args);
 
@@ -521,7 +536,7 @@ __STATIC__ int at_cmd_do_exec(at_agent_t *at_agent, const char *format, va_list
 
     at_uart_send(at_agent, (uint8_t *)at_agent->cmd_buf, cmd_len, 0xFFFF);
 
-    tos_mutex_post(&at_agent->cmd_buf_lock);
+    // tos_mutex_post(&at_agent->cmd_buf_lock);
 
     return 0;
 }
@@ -530,23 +545,29 @@ __API__ int tos_at_cmd_exec(at_agent_t *at_agent, at_echo_t *echo, uint32_t time
 {
     int ret = 0;
     va_list args;
-    
+
     if (!echo) {
         return -1;
     }
-    
+
+    if (tos_at_global_lock_pend(at_agent) != 0) {
+        return -1;
+    }
+
     if (tos_sem_create(&echo->__status_set_notify, 0) != K_ERR_NONE) {
+        tos_at_global_lock_post(at_agent);
         return -1;
     }
 
     at_echo_attach(at_agent, echo);
-    
+
     va_start(args, cmd);
     ret = at_cmd_do_exec(at_agent, cmd, args);
     va_end(args);
 
     if (ret != 0) {
         at_agent->echo = K_NULL;
+        tos_at_global_lock_post(at_agent);
         return -1;
     }
 
@@ -558,6 +579,8 @@ __API__ int tos_at_cmd_exec(at_agent_t *at_agent, at_echo_t *echo, uint32_t time
 
     at_agent->echo = K_NULL;
 
+    tos_at_global_lock_post(at_agent);
+
     return ret;
 }
 
@@ -570,7 +593,12 @@ __API__ int tos_at_cmd_exec_until(at_agent_t *at_agent, at_echo_t *echo, uint32_
         return -1;
     }
 
+    if (tos_at_global_lock_pend(at_agent) != 0) {
+        return -1;
+    }
+
     if (tos_sem_create(&echo->__expect_notify, 0) != K_ERR_NONE) {
+        tos_at_global_lock_post(at_agent);
         return -1;
     }
     echo->__is_expecting = K_TRUE;
@@ -582,6 +610,7 @@ __API__ int tos_at_cmd_exec_until(at_agent_t *at_agent, at_echo_t *echo, uint32_
 
     if (ret != 0) {
         at_agent->echo = K_NULL;
+        tos_at_global_lock_post(at_agent);
         return -1;
     }
 
@@ -593,6 +622,8 @@ __API__ int tos_at_cmd_exec_until(at_agent_t *at_agent, at_echo_t *echo, uint32_
 
     at_agent->echo = K_NULL;
 
+    tos_at_global_lock_post(at_agent);
+
     return ret;
 }
 
@@ -696,7 +727,7 @@ __API__ int tos_at_channel_read_timed(at_agent_t *at_agent, int channel_id, uint
 
     remain_tick = tos_millisec2tick(timeout);
     tos_stopwatch_countdown(&data_channel->timer, remain_tick);
-    
+
     while (!tos_stopwatch_is_expired(&data_channel->timer)) {
         remain_tick = tos_stopwatch_remain(&data_channel->timer);
         if (remain_tick == (k_tick_t)0u) {
@@ -710,7 +741,7 @@ __API__ int tos_at_channel_read_timed(at_agent_t *at_agent, int channel_id, uint
         read_len = tos_chr_fifo_pop_stream(&data_channel->rx_fifo, buffer + total_read_len, buffer_len - total_read_len);
 
         tos_mutex_post(&data_channel->rx_lock);
-        
+
         if (read_len == 0) {
             remain_tick = tos_stopwatch_remain(&data_channel->timer);
             tos_sem_pend(&data_channel->rx_sem, remain_tick);
@@ -752,13 +783,13 @@ __API__ int tos_at_channel_write(at_agent_t *at_agent, int channel_id, uint8_t *
 __STATIC_INLINE__ int at_channel_construct(at_data_channel_t *data_channel, const char *ip, const char *port, size_t socket_buffer_size)
 {
     uint8_t *fifo_buffer = K_NULL;
-    
+
     fifo_buffer = tos_mmheap_alloc(socket_buffer_size);
-    
+
     if (!fifo_buffer) {
         return -1;
     }
-    
+
     if (tos_sem_create_max(&data_channel->rx_sem, 0, 1) != K_ERR_NONE) {
         goto errout;
     }
@@ -860,7 +891,7 @@ __API__ int tos_at_channel_free(at_agent_t *at_agent, int channel_id)
     if (!data_channel) {
         return -1;
     }
-    
+
     tos_sem_destroy(&data_channel->rx_sem);
 
     tos_mutex_destroy(&data_channel->rx_lock);
@@ -957,7 +988,7 @@ __STATIC__ void tos_at_uart_input_notify(at_agent_t *at_agent)
 }
 
 __STATIC__ void idle_check_timer_callback(void *args)
-{   
+{
     at_agent_t *at_agent = (at_agent_t *)args;
     tos_at_uart_input_notify(at_agent);
 }
@@ -987,9 +1018,9 @@ __API__ int tos_at_init(at_agent_t *at_agent, char *task_name, k_stack_t *stk, h
     }
     at_agent->cmd_buf = (char *)buffer;
 
-    if (tos_mutex_create(&at_agent->cmd_buf_lock) != K_ERR_NONE) {
-        goto errout1;
-    }
+    // if (tos_mutex_create(&at_agent->cmd_buf_lock) != K_ERR_NONE) {
+    //     goto errout1;
+    // }
 
     if (at_recv_cache_init(at_agent) != 0) {
         goto errout2;
@@ -1000,9 +1031,9 @@ __API__ int tos_at_init(at_agent_t *at_agent, char *task_name, k_stack_t *stk, h
     if (!buffer) {
         goto errout3;
     }
-    
+
     at_agent->uart_rx_frame_mail_buffer = (uint8_t *)buffer;
-    
+
     if (tos_mail_q_create(&at_agent->uart_rx_frame_mail, buffer, AT_FRAME_LEN_MAIL_MAX, sizeof(at_frame_len_mail_t)) != K_ERR_NONE) {
         goto errout4;
     }
@@ -1019,22 +1050,22 @@ __API__ int tos_at_init(at_agent_t *at_agent, char *task_name, k_stack_t *stk, h
     if (tos_mutex_create(&at_agent->uart_tx_lock) != K_ERR_NONE) {
         goto errout6;
     }
-    
+
     if (tos_mutex_create(&at_agent->global_lock) != K_ERR_NONE) {
         goto errout7;
     }
-    
+
 #if AT_INPUT_SIMULATE_IDLE_EN
     if (tos_timer_create(&at_agent->idle_check_timer, SIMULATE_IDLE_DEFAULT_TIME,
         0, idle_check_timer_callback, at_agent, TOS_OPT_TIMER_ONESHOT) != K_ERR_NONE) {
         goto errout8;
     }
-#endif /* AT_INPUT_SIMULATE_IDLE_EN */  
+#endif /* AT_INPUT_SIMULATE_IDLE_EN */
 
     if (tos_hal_uart_init(&at_agent->uart, uart_port) != 0) {
         goto errout9;
     }
-    
+
     if (tos_task_create(&at_agent->parser, task_name, at_parser,
                         at_agent, AT_PARSER_TASK_PRIO, stk,
                         AT_PARSER_TASK_STACK_SIZE, 0) != K_ERR_NONE) {
@@ -1044,18 +1075,18 @@ __API__ int tos_at_init(at_agent_t *at_agent, char *task_name, k_stack_t *stk, h
     return 0;
 errout10:
     tos_hal_uart_deinit(&at_agent->uart);
-    
+
 errout9:
 #if AT_INPUT_SIMULATE_IDLE_EN
-    tos_timer_destroy(&at_agent->idle_check_timer);     
+    tos_timer_destroy(&at_agent->idle_check_timer);
 errout8:
 #endif /* AT_INPUT_SIMULATE_IDLE_EN */
-    
+
     tos_mutex_destroy(&at_agent->global_lock);
 
 errout7:
     tos_mutex_destroy(&at_agent->uart_tx_lock);
-    
+
 errout6:
 //    tos_mutex_destroy(&at_agent->uart_rx_lock);
 
@@ -1065,7 +1096,7 @@ errout6:
 #else
     tos_sem_destroy(&at_agent->uart_rx_sem);
 #endif /* AT_INPUT_TYPE_FRAME_EN */
-    
+
 #if AT_INPUT_TYPE_FRAME_EN
 errout4:
     tos_mmheap_free(at_agent->uart_rx_frame_mail_buffer);
@@ -1076,9 +1107,9 @@ errout3:
     at_recv_cache_deinit(at_agent);
 
 errout2:
-    tos_mutex_destroy(&at_agent->cmd_buf_lock);
+    // tos_mutex_destroy(&at_agent->cmd_buf_lock);
 
-errout1:
+//errout1:
     tos_mmheap_free(at_agent->cmd_buf);
     at_agent->cmd_buf = K_NULL;
 
@@ -1093,15 +1124,15 @@ errout0:
 __API__ void tos_at_deinit(at_agent_t *at_agent)
 {
     tos_task_destroy(&at_agent->parser);
-    
+
     tos_hal_uart_deinit(&at_agent->uart);
-    
+
     tos_mutex_destroy(&at_agent->global_lock);
 
     tos_mutex_destroy(&at_agent->uart_tx_lock);
 
     //tos_mutex_destroy(&at_agent->uart_tx_lock);
-    
+
 #if AT_INPUT_SIMULATE_IDLE_EN
     tos_timer_destroy(&at_agent->idle_check_timer);
 #endif /* AT_INPUT_SIMULATE_IDLE_EN */
@@ -1113,10 +1144,10 @@ __API__ void tos_at_deinit(at_agent_t *at_agent)
 #else
     tos_sem_destroy(&at_agent->uart_rx_sem);
 #endif /* AT_INPUT_TYPE_FRAME_EN */
-    
+
     at_recv_cache_deinit(at_agent);
 
-    tos_mutex_destroy(&at_agent->cmd_buf_lock);
+    // tos_mutex_destroy(&at_agent->cmd_buf_lock);
 
     tos_mmheap_free(at_agent->cmd_buf);
     at_agent->cmd_buf = K_NULL;
@@ -1136,12 +1167,12 @@ __API__ void tos_at_uart_input_frame(at_agent_t *at_agent, uint8_t *pdata, uint1
 {
     int ret;
     at_frame_len_mail_t at_frame_len_mail;
-    
+
     ret = tos_chr_fifo_push_stream(&at_agent->uart_rx_fifo, pdata, len);
     if (ret != len) {
         return;
     }
-    
+
     at_frame_len_mail.frame_len = len;
     tos_mail_q_post(&at_agent->uart_rx_frame_mail, &at_frame_len_mail, sizeof(at_frame_len_mail_t));
 }