VM_MAP_LOCK(9)

💖 VM_MAP_LOCK — the it-girl manual page (section 9, kernel devs only bestie) 💖

okay so. this is VM_MAP_LOCK(9), from the Kernel Developer's Manual, and it's literally the group chat of vm_map locking macros. like, all the little lock/unlock besties in one place. let's get into it ✨

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🌸 NAME 🌸

vm_map_lock, vm_map_unlock, vm_map_lock_read, vm_map_unlock_read, vm_map_trylock, vm_map_trylock_read, vm_map_lock_upgrade, vm_map_lock_downgrade — the vm_map locking macros, aka the whole friend group 🫶

💅 SYNOPSIS 💅

like, include these first or nothing works, iykyk:

#include <sys/param.h>
#include <vm/vm.h>
#include <vm/vm_map.h>

and here's the cast of characters 💖

void
vm_map_lock(vm_map_t map);

void
vm_map_unlock(vm_map_t map);

void
vm_map_lock_read(vm_map_t map);

void
vm_map_unlock_read(vm_map_t map);

int
vm_map_trylock(vm_map_t map);

int
vm_map_trylock_read(vm_map_t map);

int
vm_map_lock_upgrade(vm_map_t map);

int
vm_map_lock_downgrade(vm_map_t map);

✨ DESCRIPTION ✨

literally the whole vibe, one macro at a time:

• vm_map_lock() — gets an exclusive lock on map. it's giving main character energy, nobody else gets in 💅
• vm_map_unlock() — releases that exclusive lock on map. bye bestie 👋
• vm_map_lock_read() — gets a read-lock on map. you can look, just don't touch 🦋
• vm_map_unlock_read() — releases the read-lock on map. slay, we're done reading 🌸
• vm_map_trylock() — attempts to get an exclusive lock on map, but like, no waiting around. returns FALSE if the lock can't be immediately acquired; otherwise returns TRUE with the lock acquired. it's giving "if you're free, cool, if not i'm out" 😭
• vm_map_trylock_read() — same energy but for a read-lock on map. returns FALSE if the lock can't be immediately acquired; otherwise returns TRUE with the lock acquired 🔥
• vm_map_lock_upgrade() — attempts to atomically upgrade a read-lock on map to an exclusive lock. glow-up, but for locks ✨
• vm_map_lock_downgrade() — attempts to downgrade an exclusive lock on map to a read-lock. not every era needs to be the loud one, and that's okay 🎀

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🧚 IMPLEMENTATION NOTES 🧚

ngl, right now all of these locking macros implement their locks as sleep locks</> — that's the current tea, fr fr ☕

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👑 SEE ALSO 👑

• vm_map(9) — go read it, it's the source of truth bestie 🫶

💜 AUTHORS 💜

This manual page was written by Bruce M Simpson <bms@spc.org>. iconic of him, we stan 💅

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okay that's the whole page, no cap. every macro documented, nothing skipped, vibe check passed ✅

sign-off: Debian, dated July 19, 2003 — so this page is vintage, and honestly? vintage is trending again 🎀💖