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exceptionsignalsipcinterrupt
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p3t3

Reputation: 95

Is my undersanding of Interrupts, Exceptions vs signal definitions correct?

Interrupts are hardware based and happen asynchronous (data incoming to a socket, some I/O is ready to read from or write to, A user pressed the keyboard.

Exceptions are are also hardware based but they are synchronous and caused by the CPU when executing instructions. for example a page in the virtual memory address space that has no actual chunk of RAM mapped to it will cause a page fault. Exceptions are the general name for fault, trap and abort.

Interrupts and Exceptions are generated by hardware and handled by handlers in the kernel space. They can be seen as mean of communication between the Hardware and the kernel.

Signals Signals can be viewed as a mean of communication between the running processes and the kernel. In some cases an Interrupt/Exception will use signals as part of the handling by the kernel.

Upvotes: 0

Views: 302

Answers (1)

Lajos Arpad
Lajos Arpad

Reputation: 77030

Interrupts

In computing, an interrupt is an asynchronous signal indicating the need for attention or a synchronous event in software indicating the need for a change in execution.

(definition obtained from stackoverflow's tag description)

So, it's not unnecessarily asynchronous. It's asynchronous only if it is emitted by the hardware. Think of a virtual device or an emulator for examples of synchronous interrupts, when you are programming a camera and instead of the real device you have an emulator, which you can program to simulate interrupts.

Exceptions

From Microsoft docs:

Most of the standard exceptions recognized by the operating system are hardware-defined exceptions. Windows recognizes a few low-level software exceptions, but these are usually best handled by the operating system.

Windows maps the hardware errors of different processors to the exception codes in this section. In some cases, a processor may generate only a subset of these exceptions. Windows preprocesses information about the exception and issues the appropriate exception code.

Exceptions are not necessarily hardware-generated and not necessarily synchronous.

If they are synchronous, then a software emitted it (like a camera emulator). Asynchronous exceptions can be raised just about anywhere.

In more advanced programming languages one can use exception handlers and different kinds of exceptions have their own exception subclass. The program can emit an exception with a command, usually the throw keyword which is paired with an exception instance. See: https://www.geeksforgeeks.org/throw-throws-java/

One can implement custom exception classes according to business logic, see https://www.baeldung.com/java-new-custom-exception.

So, the realm of exceptions is much wider than you first thought.

Signals

A signal is a notification to a process that an event occurred. Signals are sometimes described as software interrupts. Signals are analogous to hardware interrupts in that they interrupt the normal flow of execution of a program; in most cases, it is not possible to predict exactly when a signal will arrive. They are defined in the C standards and extended in POSIX, but many other programming languages/systems provide access to them as well.

You are more-or-less correct about signals.

Upvotes: 1

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