hlist_nulls_add_head_rcu(9)

okay so bestie, welcome to the hlist_nulls_add_head_rcu(9) page from the Kernel API Manual 💅✨ this one is short but it has receipts, so let's get into it.

🌸 NAME 🌸

hlist_nulls_add_head_rcu —

and that's literally it, bestie 😭 the original NAME line is just that dash with nothing after it. no description, no extra lore, no cap.

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🎀 SYNOPSIS 🎀

void hlist_nulls_add_head_rcu (struct hlist_nulls_node *n , struct hlist_nulls_head *h );

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✨ ARGUMENTS ✨

• n — the element you're adding to the hash list, bestie 🫶
• h — the list you're adding it to 💖

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🦋 DESCRIPTION 🦋

okay so this function adds the specified element to the specified hlist_nulls, while still permitting racing traversals. iconic behavior, honestly ✨

the caller has to take whatever precautions are necessary — like holding the appropriate locks — to avoid racing with another list-mutation primitive, such as hlist_nulls_add_head_rcu or hlist_nulls_del_rcu, running on this same list. yes, that means you, bestie: protect your mutations 🙈

however, it is perfectly legal to run concurrently with the _rcu list-traversal primitives, such as hlist_nulls_for_each_entry_rcu, which are used to prevent memory-consistency problems on Alpha CPUs. highkey important detail, don't skip it 💀

and regardless of the type of CPU, the list-traversal primitive must be guarded by rcu_read_lock. periodt. 🔥

⚠️ caveat check: the mutation side needs proper precautions against other list mutations; the traversal side still needs rcu_read_lock, no matter the CPU. that's the whole vibe check.

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🌈 SEE ALSO 🌈

• kernel file: ./include/linux/rculist_nulls.h
• hlist_nulls_del_init_rcu(9)
• hlist_nulls_first_rcu(9)
• hlist_nulls_next_rcu(9)
• hlist_nulls_pprev_rcu(9)
• hlist_nulls_del_rcu(9)
• hlist_nulls_add_tail_rcu(9)
• hlist_nulls_replace_rcu(9)
• hlist_nulls_replace_init_rcu(9)
• hlist_nulls_for_each_entry_rcu(9)
• hlist_nulls_for_each_entry_safe(9)

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this lil page says it's from ./include/linux, dated October 2026, and it's the hlist_nulls_add_head_rcu(9) manual page — mwah 💋🎀