NTP overheads with RTOS

[RadianM]

I've been trying to trace why a program with several running tasks has one low priority task that never gets serviced. I found by a process of elimination that if I simply comment out the line: configTime(gmtOffset_sec, daylightOffset_sec, ntpServer) everything works as I would expect, except for the time being wrong (obviously). All my tasks yield at some point and let execution take place at all priority levels so long as I don't call configTime(). I even tried calling it from a lowest priority task of its own but that made no difference.

I haven't had any success trying to find the inner workings of NTP for arduino-esp32 as some important links seem to be to esp8266 code and some are broken. Is anyone familiar with the way NTP time is handled and how it might interfere with the task scheduler?

[markxoe]

The function you are looking for is defined here:

arduino-esp32/cores/esp32/esp32-hal-time.c

Lines 48 to 61 in c93bf11

	void configTime(long gmtOffset_sec, int daylightOffset_sec, const char* server1, const char* server2, const char* server3)
	{
	//tcpip_adapter_init(); // Should not hurt anything if already inited
	esp_netif_init();
	if(sntp_enabled()){
	sntp_stop();
	}
	sntp_setoperatingmode(SNTP_OPMODE_POLL);
	sntp_setservername(0, (char*)server1);
	sntp_setservername(1, (char*)server2);
	sntp_setservername(2, (char*)server3);
	sntp_init();
	setTimeZone(-gmtOffset_sec, daylightOffset_sec);
	}

And I suspect the esp_netif_init(); to crash your program as

this function should be called exactly once from application code, when the application starts up

(See IDF docs), but the function is already called for the WiFi stuff:

arduino-esp32/libraries/WiFi/src/WiFiGeneric.cpp

Line 618 in c93bf11

initialized = esp_netif_init() == ESP_OK;

You may need to create an issue and/or PR for this...