Sage-Tips

What is reentrant interrupt?

A reentrant interrupt handler is an interrupt handler that re-enables interrupts early in the interrupt handler. This may reduce interrupt latency. In general, while programming interrupt service routines, it is recommended to re-enable interrupts as soon as possible in the interrupt handler.

What is difference between reentrant and thread-safe code?

An operation is “thread-safe” if it can be performed from multiple threads safely, even if the calls happen simultaneously on multiple threads. An operation is re-entrant if it can be performed while the operation is already in progress (perhaps in another context).

What reentrant means?

reentering or pointing inward: a reentrant angle. noun. a reentering angle or part. a person or thing that reenters or returns: Reentrants to the engineering program must take the introductory course again.

What are non-reentrant functions?

A function can be non-reentrant if it uses memory that is not on the stack. If a function uses a static variable or a global variable, or a dynamically-allocated object that it finds for itself, then it is non-reentrant and any two calls to the function can interfere.

What make a function reentrant?

A function is said to be reentrant if there is a provision to interrupt the function in the course of execution, service the interrupt service routine and then resume the earlier going on function, without hampering its earlier course of action.

Are all reentrant functions thread-safe?

Hence, a thread-safe function is always reentrant, but a reentrant function is not always thread-safe. The class is thread-safe if its member functions can be called safely from multiple threads, even if all the threads use the same instance of the class.

How do you make a reentrant code?

To be reentrant, a computer program or routine:

1. Must hold no static (or global) non-constant data.
2. Must not return the address to static (or global) non-constant data.
3. Must work only on the data provided to it by the caller.
4. Must not rely on locks to singleton resources.

Which of the following is a reentrant function?

One function is said to be a reentrant function if there is a provision to interrupt that function in the course of execution, then service the ISR (Interrupt Service Routine) and then resume the task. This type of functions is used in different cases like, recursions, hardware interrupt handling.

What is the difference between a non-reentrant and a reentrant function?

If a function is reentrant then it can be “interrupted in the middle of its execution and then safely called again” ( Reentrancy (computing) ). If an interrupt handler is non-reentrant, then you could have undefined behavior if you receive another interrupt while your original interrupt handler is executing.

Should not call another non-reentrant function in a thread?

Should not call another non-reentrant function. Reentrancy is distinct from, but closely related to, thread-safety. A function can be thread-safe and still not reentrant.

What is the difference between a mutex and a reentrant?

For example, a function could be wrapped all around with a mutex (which avoids problems in multithreading environments), but if that function is used in an interrupt service routine, it could starve waiting for the first execution to release the mutex. The key for avoiding confusion is that reentrant refers to only one thread executing.

Why is it important to use a reentrant function in C++?

This is important because the course of action of the function should remain the same throughout the code. But, this may be allowed in case the interrupt routine uses a local copy of the reentrant function every time it uses different values or before and after the interrupt. 3. Should not call another non-reentrant function.