BLE Central: freeze on disconnect with FreeRTOS

RE: BLE Central: freeze on disconnect with FreeRTOS

Susheel Nuguru — Mon, 23 Aug 2021 07:35:13 GMT

Hi,

I am sorry but I am not able to backtrace the changes I thought were approved. So this issue still exists in app_timer_freertoc.c->app_timer_stop.c where the timer_id is dereferenced without any checks. Please make sure that you do not send a NULL as a timer_id

RE: BLE Central: freeze on disconnect with FreeRTOS

Davide Di Gesualdo — Sun, 22 Nov 2020 21:42:05 GMT

Hi everyone! I have the same issue and it is solved by applying the solution below.
FYI, I am using SDK 17.0.2 and the code in ble_conn_params.c of the on_disconnect function is the same as the one posted by KevinG.

RE: BLE Central: freeze on disconnect with FreeRTOS

Susheel Nuguru — Thu, 16 Apr 2020 11:35:48 GMT

the changes are pushed in and accepted after SDK16 was released, they should come out in SDK17

RE: BLE Central: freeze on disconnect with FreeRTOS

He!k0 — Thu, 16 Apr 2020 10:40:03 GMT

Just had the same issue on SDK16 (0098a08e2) and could solve it buy applying the suggested changing of KevinG. Looks like the pull request hasn't been accepted yet.

RE: BLE Central: freeze on disconnect with FreeRTOS

Susheel Nuguru — Tue, 17 Dec 2019 13:07:03 GMT

KevinG, your way seems cleaner than the rest. I will do a pull request to apply this change for the next release.

RE: BLE Central: freeze on disconnect with FreeRTOS

KevinG — Mon, 16 Dec 2019 22:55:08 GMT

I had a similar issue that I believe is a bug as well. on_disconnect is called inside ble_conn_params.c when BLE disconnects and it looks to stop a timer, but if the timer is null, an assertion happens. The call to stop the timer should not be made if it's null so I updated the code to check for that:

Old code:

static void on_disconnect(ble_evt_t const * p_ble_evt)
{
    ret_code_t                   err_code;
    uint16_t                     conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
    ble_conn_params_instance_t * p_instance  = instance_get(conn_handle);

    if (p_instance != NULL)
    {
    // Stop timer if running
        err_code = app_timer_stop(p_instance->timer_id);
        if (err_code != NRF_SUCCESS)
        {
            send_error_evt(err_code);
        }

        instance_free(p_instance);
    }
}

New Code:

static void on_disconnect(ble_evt_t const * p_ble_evt)
{
    ret_code_t                   err_code;
    uint16_t                     conn_handle = p_ble_evt->evt.gap_evt.conn_handle;
    ble_conn_params_instance_t * p_instance  = instance_get(conn_handle);

    if (p_instance != NULL)
    {
    // Stop timer if running
        if(p_instance->timer_id != NULL) 
        {
            err_code = app_timer_stop(p_instance->timer_id);
            if (err_code != NRF_SUCCESS)
            {
                send_error_evt(err_code);
            }
        }
        instance_free(p_instance);
    }
}

I used this method over yours because I didn't want on_disconnect throwing an error when one didn't actually exist.

RE: BLE Central: freeze on disconnect with FreeRTOS

Susheel Nuguru — Tue, 05 Nov 2019 18:01:23 GMT

nice work DjVenczel

RE: BLE Central: freeze on disconnect with FreeRTOS

Viktor Venczel — Fri, 01 Nov 2019 16:35:45 GMT

Hello everyone!

I've run into the same issue a few days ago, then luckily found this thread, I had spent lots of time to find this bug. Based on Susheel Nuguru's post I made a fix in "app_timer_freertos.c"

The timer not just never started, it is even never created, therefore a null pointer is given to the "app_timer_stop" function. If you comment out those lines, the same SDK would make problems when it is used in an application with BLE device. Hence a better fix:

uint32_t app_timer_stop(app_timer_id_t timer_id)
{
    //invalid timer
    if (timer_id == NULL)
    {
        return NRF_ERROR_INVALID_STATE;
    }

    app_timer_info_t * pinfo = (app_timer_info_t*)(timer_id);
    ...

Same applies to "app_timer_start" just to avoid future problems.

RE: BLE Central: freeze on disconnect with FreeRTOS

Susheel Nuguru — Wed, 02 Oct 2019 12:32:27 GMT

DanielK,

I found the bug you are trying to trace.

It seems that the ble_conn_params.c could have a bug that it might not be suitable for central. I am not 100% sure on that part but the problem seems to be a hardfault when trying to remove a timer from kernel queue where the timer does not exist.

The app_timer is never started in ble_conn_params.c since the negotiations were never triggered.

So in ble_conn_params.c->on_disconnect()-> comment out the app_timer_stop function as below

        // Stop timer if running
        //err_code = app_timer_stop(p_instance->timer_id);

I will discuss this internally how to handle it. But for you this workaround should fix your problem.

RE: BLE Central: freeze on disconnect with FreeRTOS

DanielK — Tue, 01 Oct 2019 13:36:55 GMT

Hi Susheel,

in the minimal example I have created a blinking LED task which stops blinking after a disconnect. I made it to make an easy reproducible example, I hope you can try it out and reproduce the behaviour. It connects to any peripheral you want which has the same device name as specified in DEVICE_NAME_PERIPHERAL.

I'm not that experienced with gdb, but by setting a breakpoint on the line 151 and stepping through the following instructions it won't get into any fault handler, but it finally stays in ulTaskNotifyTake inside the softdevice_task without allowing any possiblity to make another step in the debugger.

RE: BLE Central: freeze on disconnect with FreeRTOS

Susheel Nuguru — Tue, 01 Oct 2019 07:46:27 GMT

Hi Daniel,

You need to give us more details on what you mean by "freezes" on a disconnect event.

How did you come to the conclusion that the execution is hanging inside softdevice_task inside nrf_sdh_freertos.c task? Was there some event that your application expected that never arrived?

RE: BLE Central: freeze on disconnect with FreeRTOS

Kenneth — Thu, 26 Sep 2019 11:11:53 GMT

The FreeRTOS expert is currently out of office, but we'll try to look into this next week.