UIDINFO(9)

💖 UIDINFO(9) 💖

ok so bestie, welcome to the uidinfo page from the Kernel Developer's Manual — yes we're in section 9, we're in the kernel, we're doing UID bookkeeping and honestly? it's giving main character energy. 🎀

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✨ NAME ✨

uidinfo, uihashinit, uifind, uihold, uifree — the whole girl gang of functions for managing UID information 🫶

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✨ SYNOPSIS ✨

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/resourcevar.h>

void
uihashinit(void);

struct uidinfo *
uifind(uid_t uid);

void
uihold(struct uidinfo *uip);

void
uifree(struct uidinfo *uip);

like, copy that exactly bestie, no typos, the compiler is not forgiving 💅

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✨ DESCRIPTION ✨

The uidinfo family of functions manages uidinfo structures. Every single uidinfo structure keeps track of per-uid resource consumption counts — and we mean per uid, like one lil record per user — including the process count and the socket buffer space usage. no cap. 🌸

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🌈 uihashinit()

uihashinit() initializes the uidinfo hash table and its mutex. 🧚

⚠️ bestie, listen: this one should only be called during system initialization. it's not a "call it whenever" situation, it's a "call it once, at boot, and then never speak of it again" situation. periodt.

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🌈 uifind()

uifind() looks up and returns the uidinfo structure for uid. 🔍

And if there's no uidinfo structure chillin' there for uid yet? don't even worry, a brand new structure will be allocated and initialized for you. iconic behavior honestly.

oh and heads up — the uidinfo hash mutex is acquired and released. yes ma'am, we lock and unlock, that's just how we move here. 🔥

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🌈 uihold()

uihold() increases the reference count on uip. ✨

uip's lock is acquired and released. that's the whole thing. simple. clean. slay.

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🌈 uifree()

uifree() decreases the reference count on uip, and if that count reaches 0, uip is freed. 💀 (rip lil struct, you did amazing sweetie)

uip's lock is acquired and released, and the uidinfo hash mutex may be acquired and released too. yes, "may" — we're being precise, don't @ me. 🦋

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✨ RETURN VALUES ✨

uifind() returns a pointer to an initialized uidinfo structure — and it should not fail. like, it's not going to ghost you. it's reliable. 👑

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✨ AUTHORS ✨

This manual page was written by Chad David <davidc@acns.ab.ca>. 🫶

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and that's the whole page bestie, mwah 💅

this lil beauty is from the Debian crew and it's dated July 10, 2001 — yeah, it's an elder but it's still serving, we love her, bye bye 💖✨