1# Operating system and interrupts
2
3LVGL is **not thread-safe** by default.
4
5However, in the following conditions it's valid to call LVGL related functions:
6- In *events*. Learn more in [Events](/overview/event).
7- In *lv_timer*. Learn more in [Timers](/overview/timer).
8
9
10## Tasks and threads
11If you need to use real tasks or threads, you need a mutex which should be invoked before the call of `lv_timer_handler` and released after it.
12Also, you have to use the same mutex in other tasks and threads around every LVGL (`lv_...`) related function call and code.
13This way you can use LVGL in a real multitasking environment. Just make use of a mutex to avoid the concurrent calling of LVGL functions.
14
15Here is some pseudocode to illustrate the concept:
16
17```c
18static mutex_t lvgl_mutex;
19
20void lvgl_thread(void)
21{
22    while(1) {
23        mutex_lock(&lvgl_mutex);
24        lv_task_handler();
25        mutex_unlock(&lvgl_mutex);
26        thread_sleep(10); /* sleep for 10 ms */
27    }
28}
29
30void other_thread(void)
31{
32    /* You must always hold the mutex while using LVGL APIs */
33    mutex_lock(&lvgl_mutex);
34    lv_obj_t *img = lv_img_create(lv_scr_act());
35    mutex_unlock(&lvgl_mutex);
36
37    while(1) {
38        mutex_lock(&lvgl_mutex);
39        /* change to the next image */
40        lv_img_set_src(img, next_image);
41        mutex_unlock(&lvgl_mutex);
42        thread_sleep(2000);
43    }
44}
45```
46
47## Interrupts
48Try to avoid calling LVGL functions from interrupt handlers (except `lv_tick_inc()` and `lv_disp_flush_ready()`). But if you need to do this you have to disable the interrupt which uses LVGL functions while `lv_timer_handler` is running.
49
50It's a better approach to simply set a flag or some value in the interrupt, and periodically check it in an LVGL timer (which is run by `lv_timer_handler`).
51