LV_ASYC_CALL() segfaults while multi-threading

How-to
1

What do you want to achieve?

Call a function from a thread other than the LVGL thread

What have you tried so far?

Using lv_async_call() with a lv_lock()/lv_unlock to call a function on the next lvgl tick.

Code runs for a few seconds before segfaulting.

Code to reproduce

#include “lvgl/lvgl.h”
#include “lvgl/demos/widgets/lv_demo_widgets.h”
#include <pthread.h>

static void do_nothing(void * ptr){}

static void * nothing_thread(void *){
while(true){
lv_lock();
lv_async_call(do_nothing, NULL);
lv_unlock();
usleep(1000);
}
}

int main(){
lv_init();
lv_display_t * display = lv_sdl_window_create(1920,1080);
lv_indev_t * mouse = lv_sdl_mouse_create();
lv_demo_widgets();

pthread noThread;
pthread_create(&noThread, NULL, nothing_thread, NULL);

while(true){
lv_timer_handler_run_in_period(5);
}
}

Screenshot and/or video

Environment

  • SDL simulator (Desktop)
  • LVGL version: 9.3
2

When you call an execution of a piece of code (function) via lv_async_call(), you don’t need to call lv_lock() and lv_unlock() before and after.

3

I tried removing lv_lock() and lv_unlock(). The code still compile and runs but still segfaults shortly after

It seems to crash with the error:

Asserted at expression: block_is_free(block) && “block must be free” lv_tlsf.c:716

OR

block_locate_free: Asserted at expression: block_size(block) >= size lv_tlsf.c:774

4

Hi

Do you have #define LV_USE_OS LV_OS_PTHREAD set?

Tried your code, and with that property set, and with the lv_lock() / lv_unlock() don’t have that issue, but if either LV_USE_OS is not set or not using lv_lock() / lv_unlock() will generate the seg fault.

5

I had #define LV_USE_OS LV_OS_NONE set. After changing to LV_OS_PTHREAD it appears to have fixed the segfaulting issue. Thanks!