ib_dealloc_pd_user(9)

📦 version 7.3.1, in nixpkgs unstable

💅 ib_dealloc_pd_user(9) — aka the "bye bestie" page for your protection domain

okay so first things first, this is a page from the Kernel API Manual, and it's about ib_dealloc_pd_user — the function that says "you're done? bet, let's clean up" to a protection domain. Yes, that's a real thing. No, it's not a vibe, it's kernel verb code. 🎀

✨ NAME ✨

ib_dealloc_pd_user — deallocates a protection domain. that's it, that's the whole gig. she frees, she slays, she leaves. 💅

🌸 SYNOPSIS 🌸

int ib_dealloc_pd_user (struct ib_pd *pd , struct ib_udata *udata );

like yes, two args, both of them matter, don't come at me with "can't I just pass NULL for everything" because literally no. 🙈

🦋 ARGUMENTS 🦋

  • pd — the protection domain you're about to deallocate. this is the main character of the whole operation. she's the one getting freed. 👑
  • udata — valid user data, or NULL if this is a kernel object. so like, are you a userspace gremlin or a kernel-mode legend? pick a lane. ✨

💜 DESCRIPTION 💜

okay so here's where it gets serious, and I need you to actually focus bestie, because this is the part where people get themselves in trouble.

it is an error to call this function while any resources in the pd still exist. like, literally an error. not a "well, it usually works out" situation. not a "let's see what happens" vibe check. an ERROR. 💀

and because the kernel is not your mom, the caller — that's you — is responsible to synchronously destroy them (the resources, the ones inside pd, yes those), and guarantee no new allocations will happen. guarantee it. as in, you need to be certain. this is not a "probably fine" contract, it is a "if you mess this up you get to keep both pieces" contract. 😭

so the whole flow is: kill all the stuff inside first, make sure nothing new can spawn, and then come here and dealloc. order matters. sequencing matters. the way that teardown order is genuinely load-bearing. 🧚

⚠️ real talk: calling this with live resources still hanging around in the pd is an error, full stop. destroy them synchronously first and make sure no new allocations can happen. not a drill. 🚨

🌈 SEE ALSO 🌈

the kernel file this lives in is ./drivers/infiniband/core/verbs.c, and here's the whole friend group — go say hi, they all hang out together:

and that's the page!! 🫶 source is ./drivers/infiniband/core, dated October 2026, and the page is (obviously) ib_dealloc_pd_user(9). mwah, go free your protection domains responsibly, ily, bye!! 💖🎀🦋⭐

📦 where this page comes from