What is true for Reentrancy?

What is true for Reentrancy?

To be reentrant, a computer program or routine: Must hold no static (or global) non-constant data. Must not return the address to static (or global) non-constant data. Must work only on the data provided to it by the caller.

What makes 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.

What is Reentrancy in embedded systems?

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.

What is reentrant code and why is it needed?

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 can we avoid Reentrancy?

What is the correct way to prevent reentrancy and ensure a lock is acquired for certain operations?

1. Assign a context to one of these objects to allow it to do its work.
2. Prevent an object from being assigned a new context while it already has one.

What does a re-entrant look like?

A reentrant appears on the map as a U or V shape in the contour lines, pointing back into a hillside rather than sticking out of the hill (as would a spur). So a reentrant is a small valley, the center of which would collect water and funnel it downhill (if it were raining hard).

What does a re entrant look like?

What’s the difference between a valley and a re entrant?

As nouns the difference between valley and reentrant is that valley is an elongated depression between hills or mountains, often with a river flowing through it while reentrant is an angle or part that reenters itself.

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.

How is a reentrant function used in Stack Overflow?

The function has a state (i.e. access a global variable, or even a class member variable) This function can be called by multiple threads, or could appear twice in the stack while the process is executing (i.e. the function could call itself, directly or indirectly). Function taking callbacks as parameters smell a lot.

Is the word pure the same as reentrant?

The word pure is sometimes used interchangeably with reentrant. Like so many embedded concepts, reentrancy came from the mainframe era, in the days when memory was a valuable commodity.

Where did the idea of reentrancy come from?

Like so many embedded concepts, reentrancy came from the mainframe era, in the days when memory was a valuable commodity. In those days compilers and other programs were often written to be reentrant, so a single copy of the tool lived in memory, yet was shared by perhaps a hundred users.