Occasional core dump occurs during LVGL runtime

General discussion
1

In LVGL, there is an occasional error when clicking a button to switch pages. This issue appeared in LVGL version 8.2 and still persists in version 8.3.9. Below is the error message that occurs. Please help analyze this. Thank you.

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2

Perhaps you need to lock your threads?

3

The lv_timer_handler(); function and the lv_tick_inc(1); function in my code are mutually locked using mutexes, is that what you’re referring to? Even after adding the mutexes, it still doesn’t work.

4

Yes, thats what I mean.

… a mutex […] should be invoked before the call of lv_timer_handler and released after it. Also, you have to use the same mutex in other tasks and threads around every LVGL (lv_... ) related function call and code

So from my understanding, you need to lock like this:

        mutex_lock(&lvgl_mutex);
        lv_task_handler();
        mutex_unlock(&lvgl_mutex);

//most places in code where you use LVGL:
        mutex_lock(&lvgl_mutex);
        /* change to the next image */
        lv_img_set_src(img, next_image);
        mutex_unlock(&lvgl_mutex);

its not necessary to lock lv_tick_inc(1)

Now, since you (likely) switch pages in an event to a click, you don’t need to lock there. Because events are thread safe. But still, a crash that occurs only sometimes can point to concurrent calling of LVGL functions.

from the docs

5

How so?. If I modify a widget in LVGL inside of the event and meanwhile another thread modifies the same widget the same way that is going to cause an issue. Yes you can modify a widget in an event and not have to worry about it clashing with a thread calling lv_task_handler unless the function is being called from 2 different threads, I believe there are safeguards for that specific thing happening tho.

No part of LVGL is 100% thread safe you still have to be cautious of how things are coded even if dealing with events.

6

Thank you for your response. I will test and provide you with the final results.

7

I’m referring to this statement from the docs;

However, in the following conditions it’s valid to call LVGL related functions:

  • In events. Learn more in Events.

It may still be necessary to lock.