re-entrant code

Hello Per,

Sometimes, reentrancy is needed. Sometimes, it is not. Sometimes, as in the case of the C51 MCU, it makes sense, from an architectural point of view, to ban anything that uses reentrancy, I agree with all that.

Now: let's say I need to use reentrancy. There are several flavors of it: ISR-safe, thread-safe, recursion-safe, let's say I need something that is thread-safe. Say I'm using RTX51.

Reentrancy cannot be tested. Wicca does not work either. So I will have to be careful about what I write.

This begs the question: is there a finite checklist that I can check my code against, to ensure it is reentrant (thread-safe)?

Steph-

Now: let's say I need to use reentrancy. There are several flavors of it: ISR-safe, thread-safe, recursion-safe, let's say I need something that is thread-safe. Say I'm using RTX51.
While the '51, since it is programmable, is capable of operating with a RTOS the jumping through hoops the '51 architecture requires makes the '51 (with the exception of some PIGs, I guess) the worst possible choice for an application that requires a RTOS. When you then add reentrancy which, again, does not fit the '51 architecture you get problms piled on top of problems.

This begs the question: is there a finite checklist that I can check my code against, to ensure it is reentrant (thread-safe)?
yes, 1) check that no RTOS is involved and 2) do not call functions from ISRs.

you can, since the '51 is programmable, of course use both a RTOS and reentrant functions, but with all the concern you seems to have about "ensuring" I would strongly advise aganst it.

Erik