ATOMIC_DEC_INT(9)

💅 ATOMIC_DEC_INT(9) — the atomic decrement glow-up

okay bestie, welcome to section 9 of the Kernel Developer's Manual 🫶 this is ATOMIC_DEC_INT, and yes she's coming to you straight from the kernel-dev side of the house. buckle up, we're doing atomic decrements ✨

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🎀 NAME 🎀

atomic_dec_int, atomic_dec_int_nv, atomic_dec_long, atomic_dec_long_nv — atomic decrement operations. that's the whole vibe. four little functions, one very serious job 🔥

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✨ SYNOPSIS ✨

#include <sys/atomic.h>

void
atomic_dec_int(volatile unsigned int *p);

unsigned int
atomic_dec_int_nv(volatile unsigned int *p);

void
atomic_dec_long(volatile unsigned long *p);

unsigned long
atomic_dec_long_nv(volatile unsigned long *p);

look at her. iconic. the _nv girlies return a value, the others just do the thing and dip 💅 and yes, #include <sys/atomic.h> is mandatory, don't @ me.

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🌸 DESCRIPTION 🌸

so the atomic_dec set of functions is this interface for atomically performing decrement and decrement-and-fetch operations — and by "atomically" we mean with respect to interrupts and multiple processors in the system. like, no cap, nobody can slide in mid-operation and mess with your number. main character energy only 👑

the value referenced by the pointer p is decremented by 1. that's it. that's the whole lore. subtract one, but make it safe 🦋

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🧚 CONTEXT 🧚

atomic_dec_int(), atomic_dec_int_nv(), atomic_dec_long(), and atomic_dec_long_nv() can all be called during autoconf, from process context, or from interrupt context.

all four. every single one. any of those three places. she's flexible like that 💖

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⭐ RETURN VALUES ⭐

• atomic_dec_int and atomic_dec_long — perform the decrement without returning any knowledge of the value at p. they simply do the job and say nothing. mysterious. love that for them 🙈
• atomic_dec_int_nv and atomic_dec_long_nv — return the value at p after the decrement was performed. so you actually get the tea ☕ the _nv stands for something and she delivers.

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🦋 SEE ALSO 🦋

• atomic_add_int(9)
• atomic_inc_int(9)

the whole friend group, fr fr. go say hi 🌈

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💀 HISTORY 💀

The atomic_add functions first appeared in NetBSD 5.0 and OpenBSD 5.5.

slight plot twist: yes, the HISTORY line says atomic_add even though this page is about atomic_dec. keeping it exactly as written because that's what the manpage says, and we do not rewrite history in this house 😭

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and that's the page, bestie 💜 this edition of the kernel manual was brought to you by Debian, dated February 13, 2014 — go forth and decrement responsibly, you absolute icon 🎀✨