What is reentrant function example?

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.

What is reentrant and non-reentrant function in C?

A reentrant function does not hold static data over successive calls, nor does it return a pointer to static data. A reentrant function must not call non-reentrant functions. A non-reentrant function can often, but not always, be identified by its external interface and its usage.

What is difference between reentrant and thread safe functions?

Thread safe code is one that can be performed from multiple threads safely, even if the calls happen simultaneously on multiple threads. Reentrant code means that you can do all the things thread safe code can do but also gurantee safety even if you call the same function within the same thread.

Are Python functions reentrant?

Are all thread-safe functions reentrant? NO! A function is thread-safe if it doesn’t malfunction if called concurrently. But this can be achieved e.g. by using a mutex to block the execution of the second invocation until the first finishes, so only one invocation works at a time.

What is a reentrant lock?

A reentrant lock is a mutual exclusion mechanism that allows threads to reenter into a lock on a resource (multiple times) without a deadlock situation. A thread entering into the lock increases the hold count by one every time. Similarly, the hold count decreases when unlock is requested.

What is reentrant code?

Reentrant (multi-instance) code is a reusable routine that multiple programs can invoke, interrupt, and reinvoke simultaneously. When you want to reuse code, but associate each instance of the shared code with unique, preserved data, use reentrant code.

How do you know if a code is reentrant?

The way to determine if a function is reentrant is to analyse what it does. 2) The code is not self-modifying (fortunately, self-modifying code is relatively rare in standard C or C++).

What is the point of a reentrant lock?

What are Reentrant Locks? The ReentrantLock class implements the Lock interface and provides synchronization to methods while accessing shared resources. The code which manipulates the shared resource is surrounded by calls to lock and unlock method.

When is a function said to be 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 do you need to know about reentrant and recursion?

Reentrant function needs to be able to handle concurrent execution with different threads. Recursive function must be able to handle entry while it is still running but access is done in controlled manner and not by other threads. Thanks for contributing an answer to Stack Overflow!

What makes a routine reentrant in the embedded world?

In the embedded world a routine must satisfy the following conditions to be reentrant: It uses all shared variables in an atomic way, unless each is allocated to a specific instance of the function. It does not call non-reentrant functions. It does not use the hardware in a non-atomic way. Quite a mouthful!

What does rule 2 tell us about reentrancy?

Rule 2 tells us a calling function inherits the reentrancy problems of the callee. That makes sense. If other code inside the function trashes shared variables, the system is going to crash. Using a compiled language, though, there’s an insidious problem.