yield(), esp_yield() or delay(0) ?

[s0170071]

@TD-er just found this: esp8266/Arduino#5254
Apparently there is a difference between the three. And using the wrong one has the potential to crash the system. Were you aware of this ?

I still need to dig deeper.
If you know something about this, please enlighten me.

[TD-er]

I already used esp_yield() in a call.

The main different is that esp_yield will test if it is being run from cont stack or system stack.
So it is a safe call to yield for use in callback functions, since they may or may not be run from cont stack.
This will only make a difference if the error is about incorrect use of yield.

Not sure what the delay(0) does different from delay(1), apart from probably being 1 msec faster ;)

[uzi18]

esp_yield(): ESP8266Ping only
there are quiet some places where delay(1) could be changed into delay(0), as we not need delay but be sure system is stable.

[TD-er]

There are not that many places anymore where we are calling delay with 1, are there?

[ascillato]

in the Arduino core, they change a yield() for esp_yield() and the webserver got unresponsive.

See esp8266/Arduino#5259

So, a delay(0) was the solution there to avoid the issue.

[uzi18]

@TD-er 110 places only in ESPEasy, did not count in libraries

[TD-er]

OK, good to know.
I will have to look at the source code to see what is the difference between delay(0) and yield(), although I have some idea, but maybe not yet all the details present.
@ascillato do you have a link already? Otherwise I will have a look tomorrow.

Edit:
Found it:
https://github.com/esp8266/Arduino/blob/74819a763bfb6e9890a57411dcea4aba221a778d/cores/esp8266/core_esp8266_wiring.c#L43-L54

[TD-er]

@ascillato
Is it possible the core library has changed in such a way that delay(0) does feed the watchdog timer and yield() no longer does?
I that is true, then what is the use for yield() compared to delay(0) ?

[ascillato]

@TD-er I really don't know. Sorry. May be we need to ask that to Arduino Guys.

[s0170071]

Maybe @d-a-v or @earlephilhower can shed some light on the difference between esp_yield(), yield() or sleep(0) They were participating in the issue referenced in the first post.

[d-a-v]

Maybe an issue should be opened in the core repository, with the very same title.
Simple answer is: do not use esp_yield(). Calling yield() in ISR or some callbacks will panic(). Calling delay(0) has the yield() effect without panicing but is missing the cont_check test.
Hopefully igrr would comment on this.

[Grovkillen]

I will close this, open if its still a valid issue.