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Operating Systems: Virtualization, Concurrency & Persistence

Fetch-And-Add

Let's look at one last hardware primitive for building locks, the fetch-and-add instruction.

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One final hardware primitive is the fetch-and-add instruction, which atomically increments a value while returning the old value at a particular address. The C pseudocode for the fetch-and-add instruction looks like this:

int FetchAndAdd(int *ptr) {
    int old = *ptr;
    *ptr = old + 1;
    return old;
}

TIP: LESS CODE IS BETTER CODE (LAUER’S LAW)

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