computer science

Inter-processor interrupt

Inter-processor interrupt is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Inter-processor interrupt rather than just read about it. In short: In computing, an inter-processor interrupt (IPI), also known as a shoulder tap, is a special type of interrupt by which one processor may interrupt another processor in a multiprocessor system if the interrupting processor requires action from the other processor. Actions that might be requested include: Flush memory management unit caches, such as translation lookaside buffers, on other processors when memory mappi…

Key takeaways

Inter-processor interrupt belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Inter-processor interrupt to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Inter-processor interrupt from memory before moving on to harder problems.

Reference excerpt

In computing, an inter-processor interrupt (IPI), also known as a shoulder tap, is a special type of interrupt by which one processor may interrupt another processor in a multiprocessor system if the interrupting processor requires action from the other processor. Actions that might be requested include:

Flush memory management unit caches, such as translation lookaside buffers, on other processors when memory mappings are changed by one processor; Stop when the system is being shut down by one processor. Notify an alternate CPU of a malfunction for Alternate CPU Recovery (ACR). Notify a processor that higher-priority work is available. Notify a processor of work that cannot be done on all processors due to, e.g., asymmetric access to I/O channels special features on some processors

Mechanism The M65MP option of OS/360 used the Direct Control feature of the S/360 to generate an interrupt on another processor; on S/370 and its successors, including z/Architecture, the SIGNAL PROCESSOR instruction provides a more formalized interface. The documentation for some IBM operating systems refers to this as a shoulder tap. On IBM PC compatible computers that use the Advanced Programmable Interrupt Controller (APIC), IPI signaling is often performed using the APIC. When a CPU wishes to send an interrupt to another CPU, it stores the interrupt vector and the identifier of the target's local APIC in the Interrupt Command Register (ICR) of its own local APIC. A message is then sent via the APIC bus to the target's local APIC, which then issues a corresponding interrupt to its own CPU.

Examples

Windows In a multiprocessor system running Microsoft Windows, a processor may interrupt another processor for the following reasons, in addition to the ones listed above:

queue a DISPATCH_LEVEL interrupt to schedule a particular thread for execution; kernel debugger breakpoint. IPIs are given an IRQL of 29.

See also Interrupt Interrupt handler Non-maskable interrupt (NMI)

References

External links Interrupts and Exceptions

Worked examples

Example 1 — a first encounter with Inter-processor interrupt

Start with the simplest possible case. Write down what Inter-processor interrupt claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Inter-processor interrupt before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Inter-processor interrupt ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Inter-processor interrupt

In research: Inter-processor interrupt appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Inter-processor interrupt in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Inter-processor interrupt is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer hardware stubs, Interrupts, so understanding it makes those chapters shorter.
In everyday life: Look for Inter-processor interrupt outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Inter-processor interrupt in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Inter-processor interrupt means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Inter-processor interrupt out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Inter-processor interrupt in simple terms?

Why does Inter-processor interrupt matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Inter-processor interrupt?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Inter-processor interrupt.