bt_conn_disconnect() - ASSERTION FAILED [err == 0] k_sem_take return err -11

Question

Hi, 
 I just started developing a BLE Central device on a nRF52840 DK. After successfully connect my DevKit with a phone acting as a peripheral (using nRF Connect Mobile), The DK was able to subscribe to some services I configured on the phone and receive the corresponding notifications. 
 Right now I'm trying to disconnect every BLE connections the DK has when a specific button is pressed. I managed to init the button and to add a callback function on it. The function works great but when I'm trying to disconnect the peripheral, I got an error: 
 
 ASSERTION FAIL [err == 0] @ ZEPHYR_BASE/subsys/bluetooth/host/hci_core.c:306 k_sem_take failed with err -11 
 
 This is the part of my code that should disconnect every BLE connection that the central has: 
 static void disconnect(struct bt_conn *conn, void *data)
{
 char addr[BT_ADDR_LE_STR_LEN];
 
 bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));
 printk("Disconnecting %s...
", addr);

int err = bt_conn_disconnect(conn, BT_HCI_ERR_REMOTE_USER_TERM_CONN);
 if (err)
 {
 printk("Failed disconnection %s
", addr);
 }
 else
 {
 printk("Success
");
 }
}

void ble_disconnect_all(void)
{ 
 bt_conn_foreach(BT_CONN_TYPE_LE, disconnect, NULL);
} 
 The function ble_disconnect_all(void) is called when the button1 is pressed, the printk("Disconnecting %s...
", addr) is actually printed but when the program called bt_conn_disconnect(conn, BT_HCI_REMOTE_USER_TERM_CONN) , then I get the error above. 
 I look up to the hci_core.c at the line 306. It's in the function called bt_hci_cmd_send_sync() . In this function, k_sem_take(&sync_sem, HCI_CMD_TIMEOUT) tried to take a semaphore, failed and then the BT_ASSERT_MSG() triggered. The message appears immediately when I pressed the button, it doesn't wait the 10 seconds that is configure by default in HCI_CMD_TIMEOUT . 
 Since this error appears, the program seems to be frozen. Nothing happen when I manually disconnect my phone (either by disabling the bluetooth or just by pressing the Disconnect option in nRF Connect Mobile). The only way I found to unfroze the device is by turning it off/on. 
 My setup 
 
 Ubuntu 22.04 in WSL2 (Host OS is Windows 10) 
 PlatformIO CLI, version 6.1.15 
 Zephyr framework, version 2.20701.220422 
 
 Prj.conf: 
 CONFIG_BT=y CONFIG_BT_DEVICE_NAME="BLE_test" CONFIG_BT_CENTRAL=y CONFIG_BT_GATT_CLIENT=y CONFIG_CONSOLE=y CONFIG_GPIO=y

Hieu · Accepted Answer

Hi Victor, 
 In your code, last_press_time could be volatile , which helps ensuring that the value is up to date. It could also be local to the callback, but that should not affect performance/behavior. 
 printk() by default is in-place and blocking , so the printk() calls will prolong the execution of the callback. It might be a good idea to replace them with Logging APIs or CONFIG_LOG_PRINTK , both together with CONFIG_LOG_MODE_DEFERRED , to make printk() non-blocking. 
 Otherwise, I think the logic is reasonable. I also discuss a bit further on debouncing here: Zephyr debounce support 
 Please let me know if the flag handling improves the situation. If that works, you might also want to consider upgrading it to using workqueue or other Zephyr kernel services . 
 Regards, 
 Hieu

Susheel Nuguru · Answer

Victor, I think the reason you have the garbage after the device name is because log_strdup does not make use of the struct bt_data->datalen. 
 Easiest would be to append a '\0' to data->data[bt_data->data_len] and then log_strdup might handle this better. 
 I am also unsure why bt_conn_foreach does not work for disconnecting for each connection. If you are pretty sure that you have more than one device connected at this point, then bt_conn_foreach should have looped through them. I did a quick test at my end and it seems that it disconnects both devices that I was connected to.

bt_conn_disconnect() - ASSERTION FAILED [err == 0] k_sem_take return err -11

My setup

Top Replies