RE: Bluetooth RPC Stack Hangs When Running a Second BLE Scan

Amr Moussa — Tue, 04 Oct 2022 14:21:22 GMT

After inspecting your code I was able to resolve the issue. The problem is that I was calling bt_le_scan_stop() in a timer handler thread. If my understanding is correct, timer handlers are "interrupt threads" which do not get to live for very long, and it seems not long enough to properly shut down BLE scanning. I moved my bt_le_scan_stop() call into a work queue job that is submitted to the queue from the timer handler and that resolved the issue. Thank you for your help!

RE: Bluetooth RPC Stack Hangs When Running a Second BLE Scan

Sigurd — Mon, 26 Sep 2022 11:53:12 GMT

I'm not able to reproduce it.

I tried using central_uart sample with some modification. Here is the code I used:

/*
 * Copyright (c) 2018 Nordic Semiconductor ASA
 *
 * SPDX-License-Identifier: LicenseRef-Nordic-5-Clause
 */

/** @file
 *  @brief Nordic UART Service Client sample
 */

#include <errno.h>
#include <zephyr/kernel.h>
#include <zephyr/device.h>
#include <zephyr/devicetree.h>
#include <zephyr/sys/byteorder.h>
#include <zephyr/sys/printk.h>

#include <zephyr/types.h>
#include <zephyr/kernel.h>

#include <zephyr/bluetooth/bluetooth.h>
#include <zephyr/bluetooth/hci.h>
#include <zephyr/bluetooth/conn.h>
#include <zephyr/bluetooth/uuid.h>
#include <zephyr/bluetooth/gatt.h>

#include <bluetooth/services/nus.h>
#include <bluetooth/services/nus_client.h>
#include <bluetooth/gatt_dm.h>
#include <bluetooth/scan.h>

#include <zephyr/settings/settings.h>

#include <zephyr/drivers/uart.h>

#include <zephyr/logging/log.h>

#define LOG_MODULE_NAME central_uart
LOG_MODULE_REGISTER(LOG_MODULE_NAME);

/* UART payload buffer element size. */
#define UART_BUF_SIZE 20

#define KEY_PASSKEY_ACCEPT DK_BTN1_MSK
#define KEY_PASSKEY_REJECT DK_BTN2_MSK

#define NUS_WRITE_TIMEOUT K_MSEC(150)
#define UART_WAIT_FOR_BUF_DELAY K_MSEC(50)
#define UART_RX_TIMEOUT 50

static const struct device *uart = DEVICE_DT_GET(DT_NODELABEL(uart0));
static struct k_work_delayable uart_work;

K_SEM_DEFINE(nus_write_sem, 0, 1);

struct uart_data_t {
	void *fifo_reserved;
	uint8_t  data[UART_BUF_SIZE];
	uint16_t len;
};

static K_FIFO_DEFINE(fifo_uart_tx_data);
static K_FIFO_DEFINE(fifo_uart_rx_data);

static struct bt_conn *default_conn;
static struct bt_nus_client nus_client;

static void ble_data_sent(struct bt_nus_client *nus, uint8_t err,
					const uint8_t *const data, uint16_t len)
{
	ARG_UNUSED(nus);

	struct uart_data_t *buf;

	/* Retrieve buffer context. */
	buf = CONTAINER_OF(data, struct uart_data_t, data);
	k_free(buf);

	k_sem_give(&nus_write_sem);

	if (err) {
		LOG_WRN("ATT error code: 0x%02X", err);
	}
}

static uint8_t ble_data_received(struct bt_nus_client *nus,
						const uint8_t *data, uint16_t len)
{
	ARG_UNUSED(nus);

	int err;

	for (uint16_t pos = 0; pos != len;) {
		struct uart_data_t *tx = k_malloc(sizeof(*tx));

		if (!tx) {
			LOG_WRN("Not able to allocate UART send data buffer");
			return BT_GATT_ITER_CONTINUE;
		}

		/* Keep the last byte of TX buffer for potential LF char. */
		size_t tx_data_size = sizeof(tx->data) - 1;

		if ((len - pos) > tx_data_size) {
			tx->len = tx_data_size;
		} else {
			tx->len = (len - pos);
		}

		memcpy(tx->data, &data[pos], tx->len);

		pos += tx->len;

		/* Append the LF character when the CR character triggered
		 * transmission from the peer.
		 */
		if ((pos == len) && (data[len - 1] == '\r')) {
			tx->data[tx->len] = '\n';
			tx->len++;
		}

		err = uart_tx(uart, tx->data, tx->len, SYS_FOREVER_MS);
		if (err) {
			k_fifo_put(&fifo_uart_tx_data, tx);
		}
	}

	return BT_GATT_ITER_CONTINUE;
}

static void uart_cb(const struct device *dev, struct uart_event *evt, void *user_data)
{
	ARG_UNUSED(dev);

	static size_t aborted_len;
	struct uart_data_t *buf;
	static uint8_t *aborted_buf;
	static bool disable_req;

	switch (evt->type) {
	case UART_TX_DONE:
		LOG_DBG("UART_TX_DONE");
		if ((evt->data.tx.len == 0) ||
		    (!evt->data.tx.buf)) {
			return;
		}

		if (aborted_buf) {
			buf = CONTAINER_OF(aborted_buf, struct uart_data_t,
					   data);
			aborted_buf = NULL;
			aborted_len = 0;
		} else {
			buf = CONTAINER_OF(evt->data.tx.buf,
					   struct uart_data_t,
					   data);
		}

		k_free(buf);

		buf = k_fifo_get(&fifo_uart_tx_data, K_NO_WAIT);
		if (!buf) {
			return;
		}

		if (uart_tx(uart, buf->data, buf->len, SYS_FOREVER_MS)) {
			LOG_WRN("Failed to send data over UART");
		}

		break;

	case UART_RX_RDY:
		LOG_DBG("UART_RX_RDY");
		buf = CONTAINER_OF(evt->data.rx.buf, struct uart_data_t, data);
		buf->len += evt->data.rx.len;

		if (disable_req) {
			return;
		}

		if ((evt->data.rx.buf[buf->len - 1] == '\n') ||
		    (evt->data.rx.buf[buf->len - 1] == '\r')) {
			disable_req = true;
			uart_rx_disable(uart);
		}

		break;

	case UART_RX_DISABLED:
		LOG_DBG("UART_RX_DISABLED");
		disable_req = false;

		buf = k_malloc(sizeof(*buf));
		if (buf) {
			buf->len = 0;
		} else {
			LOG_WRN("Not able to allocate UART receive buffer");
			k_work_reschedule(&uart_work, UART_WAIT_FOR_BUF_DELAY);
			return;
		}

		uart_rx_enable(uart, buf->data, sizeof(buf->data),
			       UART_RX_TIMEOUT);

		break;

	case UART_RX_BUF_REQUEST:
		LOG_DBG("UART_RX_BUF_REQUEST");
		buf = k_malloc(sizeof(*buf));
		if (buf) {
			buf->len = 0;
			uart_rx_buf_rsp(uart, buf->data, sizeof(buf->data));
		} else {
			LOG_WRN("Not able to allocate UART receive buffer");
		}

		break;

	case UART_RX_BUF_RELEASED:
		LOG_DBG("UART_RX_BUF_RELEASED");
		buf = CONTAINER_OF(evt->data.rx_buf.buf, struct uart_data_t,
				   data);

		if (buf->len > 0) {
			k_fifo_put(&fifo_uart_rx_data, buf);
		} else {
			k_free(buf);
		}

		break;

	case UART_TX_ABORTED:
		LOG_DBG("UART_TX_ABORTED");
		if (!aborted_buf) {
			aborted_buf = (uint8_t *)evt->data.tx.buf;
		}

		aborted_len += evt->data.tx.len;
		buf = CONTAINER_OF(aborted_buf, struct uart_data_t,
				   data);

		uart_tx(uart, &buf->data[aborted_len],
			buf->len - aborted_len, SYS_FOREVER_MS);

		break;

	default:
		break;
	}
}

static void uart_work_handler(struct k_work *item)
{
	struct uart_data_t *buf;

	buf = k_malloc(sizeof(*buf));
	if (buf) {
		buf->len = 0;
	} else {
		LOG_WRN("Not able to allocate UART receive buffer");
		k_work_reschedule(&uart_work, UART_WAIT_FOR_BUF_DELAY);
		return;
	}

	uart_rx_enable(uart, buf->data, sizeof(buf->data), UART_RX_TIMEOUT);
}

static int uart_init(void)
{
	int err;
	struct uart_data_t *rx;

	if (!device_is_ready(uart)) {
		LOG_ERR("UART device not ready");
		return -ENODEV;
	}

	rx = k_malloc(sizeof(*rx));
	if (rx) {
		rx->len = 0;
	} else {
		return -ENOMEM;
	}

	k_work_init_delayable(&uart_work, uart_work_handler);

	err = uart_callback_set(uart, uart_cb, NULL);
	if (err) {
		return err;
	}

	return uart_rx_enable(uart, rx->data, sizeof(rx->data),
			      UART_RX_TIMEOUT);
}

static void discovery_complete(struct bt_gatt_dm *dm,
			       void *context)
{
	struct bt_nus_client *nus = context;
	LOG_INF("Service discovery completed");

	bt_gatt_dm_data_print(dm);

	bt_nus_handles_assign(dm, nus);
	bt_nus_subscribe_receive(nus);

	bt_gatt_dm_data_release(dm);
}

static void discovery_service_not_found(struct bt_conn *conn,
					void *context)
{
	LOG_INF("Service not found");
}

static void discovery_error(struct bt_conn *conn,
			    int err,
			    void *context)
{
	LOG_WRN("Error while discovering GATT database: (%d)", err);
}

struct bt_gatt_dm_cb discovery_cb = {
	.completed         = discovery_complete,
	.service_not_found = discovery_service_not_found,
	.error_found       = discovery_error,
};

static void gatt_discover(struct bt_conn *conn)
{
	int err;

	if (conn != default_conn) {
		return;
	}

	err = bt_gatt_dm_start(conn,
			       BT_UUID_NUS_SERVICE,
			       &discovery_cb,
			       &nus_client);
	if (err) {
		LOG_ERR("could not start the discovery procedure, error "
			"code: %d", err);
	}
}

static void exchange_func(struct bt_conn *conn, uint8_t err, struct bt_gatt_exchange_params *params)
{
	if (!err) {
		LOG_INF("MTU exchange done");
	} else {
		LOG_WRN("MTU exchange failed (err %" PRIu8 ")", err);
	}
}

static void connected(struct bt_conn *conn, uint8_t conn_err)
{
	char addr[BT_ADDR_LE_STR_LEN];
	int err;

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	if (conn_err) {
		LOG_INF("Failed to connect to %s (%d)", addr, conn_err);

		if (default_conn == conn) {
			bt_conn_unref(default_conn);
			default_conn = NULL;

			err = bt_scan_start(BT_SCAN_TYPE_SCAN_ACTIVE);
			if (err) {
				LOG_ERR("Scanning failed to start (err %d)",
					err);
			}
		}

		return;
	}

	LOG_INF("Connected: %s", addr);

	static struct bt_gatt_exchange_params exchange_params;

	exchange_params.func = exchange_func;
	err = bt_gatt_exchange_mtu(conn, &exchange_params);
	if (err) {
		LOG_WRN("MTU exchange failed (err %d)", err);
	}

	err = bt_conn_set_security(conn, BT_SECURITY_L2);
	if (err) {
		LOG_WRN("Failed to set security: %d", err);

		gatt_discover(conn);
	}

	err = bt_scan_stop();
	if ((!err) && (err != -EALREADY)) {
		LOG_ERR("Stop LE scan failed (err %d)", err);
	}
}

static void disconnected(struct bt_conn *conn, uint8_t reason)
{
	char addr[BT_ADDR_LE_STR_LEN];
	int err;

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Disconnected: %s (reason %u)", addr, reason);

	if (default_conn != conn) {
		return;
	}

	bt_conn_unref(default_conn);
	default_conn = NULL;

	err = bt_scan_start(BT_SCAN_TYPE_SCAN_ACTIVE);
	if (err) {
		LOG_ERR("Scanning failed to start (err %d)",
			err);
	}
}

static void security_changed(struct bt_conn *conn, bt_security_t level,
			     enum bt_security_err err)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	if (!err) {
		LOG_INF("Security changed: %s level %u", addr, level);
	} else {
		LOG_WRN("Security failed: %s level %u err %d", addr,
			level, err);
	}

	gatt_discover(conn);
}

BT_CONN_CB_DEFINE(conn_callbacks) = {
	.connected = connected,
	.disconnected = disconnected,
	.security_changed = security_changed
};

static void scan_filter_match(struct bt_scan_device_info *device_info,
			      struct bt_scan_filter_match *filter_match,
			      bool connectable)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(device_info->recv_info->addr, addr, sizeof(addr));

	LOG_INF("Filters matched. Address: %s connectable: %d",
		addr, connectable);
}

static void no_match_fun(struct bt_scan_device_info *device_info,
			      struct bt_scan_filter_match *filter_match,
			      bool connectable)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(device_info->recv_info->addr, addr, sizeof(addr));

	LOG_INF("Filters not matched. Address: %s connectable: %d",
		addr, connectable);
}

static void scan_connecting_error(struct bt_scan_device_info *device_info)
{
	LOG_WRN("Connecting failed");
}

static void scan_connecting(struct bt_scan_device_info *device_info,
			    struct bt_conn *conn)
{
	default_conn = bt_conn_ref(conn);
}

static int nus_client_init(void)
{
	int err;
	struct bt_nus_client_init_param init = {
		.cb = {
			.received = ble_data_received,
			.sent = ble_data_sent,
		}
	};

	err = bt_nus_client_init(&nus_client, &init);
	if (err) {
		LOG_ERR("NUS Client initialization failed (err %d)", err);
		return err;
	}

	LOG_INF("NUS Client module initialized");
	return err;
}

BT_SCAN_CB_INIT(scan_cb, scan_filter_match, no_match_fun,
		scan_connecting_error, scan_connecting);

static int scan_init(void)
{
	int err;
	struct bt_scan_init_param scan_init = {
		.connect_if_match = 0,
	};

	bt_scan_init(&scan_init);
	bt_scan_cb_register(&scan_cb);

	err = bt_scan_filter_add(BT_SCAN_FILTER_TYPE_UUID, BT_UUID_NUS_SERVICE);
	if (err) {
		LOG_ERR("Scanning filters cannot be set (err %d)", err);
		return err;
	}

	err = bt_scan_filter_enable(BT_SCAN_UUID_FILTER, false);
	if (err) {
		LOG_ERR("Filters cannot be turned on (err %d)", err);
		return err;
	}

	LOG_INF("Scan module initialized");
	return err;
}


static void auth_cancel(struct bt_conn *conn)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Pairing cancelled: %s", addr);
}


static void pairing_complete(struct bt_conn *conn, bool bonded)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_INF("Pairing completed: %s, bonded: %d", addr, bonded);
}


static void pairing_failed(struct bt_conn *conn, enum bt_security_err reason)
{
	char addr[BT_ADDR_LE_STR_LEN];

	bt_addr_le_to_str(bt_conn_get_dst(conn), addr, sizeof(addr));

	LOG_WRN("Pairing failed conn: %s, reason %d", addr, reason);
}

static struct bt_conn_auth_cb conn_auth_callbacks = {
	.cancel = auth_cancel,
};

static struct bt_conn_auth_info_cb conn_auth_info_callbacks = {
	.pairing_complete = pairing_complete,
	.pairing_failed = pairing_failed
};

void main(void)
{
	int err;

	err = bt_conn_auth_cb_register(&conn_auth_callbacks);
	if (err) {
		LOG_ERR("Failed to register authorization callbacks.");
		return;
	}

	err = bt_conn_auth_info_cb_register(&conn_auth_info_callbacks);
	if (err) {
		printk("Failed to register authorization info callbacks.\n");
		return;
	}

	err = bt_enable(NULL);
	if (err) {
		LOG_ERR("Bluetooth init failed (err %d)", err);
		return;
	}
	LOG_INF("Bluetooth initialized");

	if (IS_ENABLED(CONFIG_SETTINGS)) {
		settings_load();
	}

	int (*module_init[])(void) = {uart_init, scan_init, nus_client_init};
	for (size_t i = 0; i < ARRAY_SIZE(module_init); i++) {
		err = (*module_init[i])();
		if (err) {
			return;
		}
	}

	printk("Starting Bluetooth Central UART example\n");


	err = bt_scan_start(BT_SCAN_TYPE_SCAN_ACTIVE);
	if (err) {
		LOG_ERR("Scanning failed to start (err %d)", err);
		return;
	}

	LOG_INF("Scanning successfully started");

	for (;;) {
		/* Wait indefinitely for data to be sent over Bluetooth */
		struct uart_data_t *buf = k_fifo_get(&fifo_uart_rx_data,
						     K_FOREVER);

		err = bt_nus_client_send(&nus_client, buf->data, buf->len);
		if (err) {
			LOG_WRN("Failed to send data over BLE connection"
				"(err %d)", err);
		}

		err = k_sem_take(&nus_write_sem, NUS_WRITE_TIMEOUT);
		if (err) {
			LOG_WRN("NUS send timeout");
		}
	}
}

void ble_scan_stop_start_thread(void)
{
	int err;
	while(true){

	k_sleep(K_MSEC(5000));

	err = bt_le_scan_stop();
	if (err) {
		LOG_ERR("Scanning failed to stop (err %d)", err);
	}
	else{
			LOG_INF("Scanning stopped");
	}


	k_sleep(K_MSEC(5000));

	err = bt_scan_start(BT_SCAN_TYPE_SCAN_ACTIVE);
	if (err) {
		LOG_ERR("Scanning failed to start (err %d)", err);
	}
	else{
			LOG_INF("Scanning started");
	}


	}


}

K_THREAD_DEFINE(ble_scan_stop_start_thread_id, 1024, ble_scan_stop_start_thread, NULL, NULL,
		NULL, 7, 0, 0);

I have a thread that is stopping/starting the scanning called ble_scan_stop_start_thread, and I don't see any hanging when the scanning starts again.

RE: Bluetooth RPC Stack Hangs When Running a Second BLE Scan

Amr Moussa — Thu, 22 Sep 2022 18:40:24 GMT

I am still experiencing the same issue on 2.1.0 and the main branch.

RE: Bluetooth RPC Stack Hangs When Running a Second BLE Scan

Sigurd — Wed, 21 Sep 2022 12:30:37 GMT

Hi,

This should now be fixed. I tested again now with nRF Connect SDK version 2.1.0, and I could no longer reproduce the issue.

RE: Bluetooth RPC Stack Hangs When Running a Second BLE Scan

Sigurd — Fri, 19 Aug 2022 11:17:29 GMT

Hi,

I see similar behavior here as well. We are looking into it.

RE: Bluetooth RPC Stack Hangs When Running a Second BLE Scan

Amr Moussa — Thu, 18 Aug 2022 13:52:19 GMT

Any updates on this ticket?

RE: Bluetooth RPC Stack Hangs When Running a Second BLE Scan

Amr Moussa — Mon, 15 Aug 2022 14:37:26 GMT

I have replicated the issue with both version 2.02 and the latest main branch.

RE: Bluetooth RPC Stack Hangs When Running a Second BLE Scan

Sigurd — Mon, 15 Aug 2022 13:02:11 GMT

Hi,

I'm not aware of any issues that could cause this. I can try to reproduce it here. What version of nRF Connect SDK are you using?