blocking_not...ain_register(9)

💅 blocking_notifier_chain_register(9)

okay so you found yourself in the Kernel API Manual and the page is literally called blocking_not...ain_register(9) (they truncated it, not me, don't come for me 🫶). It's a kernel function page, it's short, it's sweet, and we're gonna get through it together. no cap.

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✨ NAME ✨

blocking_notifier_chain_register — the function that Add notifier to a blocking notifier chain. that's it, that's the tweet. 📌

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🌸 SYNOPSIS 🌸

here's the whole vibe in one line, take it in:

int blocking_notifier_chain_register (struct blocking_notifier_head *nh , struct notifier_block *n );

so it returns an int, and it takes two things. live laugh love. 💖

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🎀 ARGUMENTS 🎀

okay bestie, the two things:

• nh — Pointer to head of the blocking notifier chain. it's the head, it's the main character, everything hangs off it 👑
• n — New entry in notifier chain. this is the new kid joining the group chat 🦋

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⭐ DESCRIPTION ⭐

So what does it do? It adds a notifier to a blocking notifier chain — literally what it says on the tin, no plot twist.

🌈 Big important caveat incoming: this must be called in process context. Not interrupt. Not atomic. Process context. noted and filed, fr fr.

And the returns, because we love a clean contract:

• Returns 0 on success 🎉
• Returns -EEXIST on error (translation: that entry already exists, it's giving "you're already in this gc" 💀)

that's the entire description. short queen. ate and left no crumbs. 💅

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🧚 SEE ALSO 🧚

these are all the siblings, the whole notifier family reunion, no one left out:

• Kernel file ./kernel/notifier.c
• notifier_call_chain(9)
• notifier_call_chain_robust(9)
• atomic_notifier_chain_register(9)
• atomic_notifier_chain_register_unique_prio(9)
• atomic_notifier_chain_unregister(9)
• atomic_notifier_call_chain(9)
• atomic_notifier_call_chain_is_empty(9)
• blocking_notifier_chain_register_unique_prio(9)
• blocking_notifier_chain_unregister(9)
• blocking_notifier_call_chain(9)
• raw_notifier_chain_register(9)
• raw_notifier_chain_unregister(9)
• raw_notifier_call_chain(9)
• srcu_notifier_chain_register(9)
• srcu_notifier_chain_unregister(9)
• srcu_notifier_call_chain(9)
• srcu_init_notifier_head(9)

like, the whole roster. go read them too, iykyk 📚✨

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🍓 one last reminder before you go: process context. that's the one. don't embarrass me in front of the kernel.

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and that's a wrap on this little page 🫶 straight from ./kernel, dated October 2026, and yes the footer still spells it blocking_not...ain_register(9) — it's iconic, we're keeping it. bye bestie, go register some notifiers responsibly 💜