Re: C functions in Lua coroutines

[Johann ''Myrkraverk'' Oskarsson <johann+lua@...>]

On 3/28/2023 2:28 PM, Schmalzer, Lukas wrote:
> Hello,
>
> I don’t know if it was ever discussed, that when you call C functions in 
> Lua coroutines, the whole Lua system is blocked, i.e., no coroutine can 
> advance.
>
> Currently there is no way to yield from C. This behavior is problematic 
> for time critical applications, e.g., as in our application, the 
> execution environment for machine sequences.
>
> We implemented a way to yield from C, i.e., only the coroutine executing 
> the long running C code is blocked.
>
> As a solution, we create a coroutine in the interpreter (C code) for 
> each coroutine in the Lua code. We applied the solution to the blocking 
> C functions in “io” and “os” (liolib.c and loslib.c).
>
> Of course, we are aware, that this cannot be a general solution, as 
> existing code would not expect yields from these libraries. Maybe a 
> separate library with functions to yield from C would be a good approach.
>
> The yield from C feature makes most sense for custom, application 
> specific C libraries.
>
> I think that the possibility to yield from C would be a useful feature 
> for the interpreter, because not the whole Lua system needs to block 
> when a long running C function is executed.
>
> Please let me know what you think about this feature.

I only skimmed that chapter, but isn't exactly this covered in chapter
29.2 in /Programming in Lua/ 4th edition?


Johann