rhashtable_lookup_fast(9)

💖 NAME — rhashtable_lookup_fast(9) from the Kernel API Manual 💖

okay so bestie, this is the Kernel API Manual page for rhashtable_lookup_fast, and it does exactly what it says on the tin: search hash table, without RCU read lock. no cap, that's the whole NAME vibe. 🦋

✨ SYNOPSIS ✨

void * rhashtable_lookup_fast (struct rhashtable *ht , const void *key ,
       const struct rhashtable_params params );

🎀 ARGUMENTS 🎀

• ht — hash table. the main character. 👑
• key — the pointer to the key. literally the pointer to the key. 🔑
• params — hash table parameters. the settings, the vibe config. ⚙️

🌸 DESCRIPTION 🌸

okay so here's the tea: it computes the hash value for the key, then traverses the bucket chain looking for an entry with an identical key. the first matching entry is returned. that's it, that's the lookup. 💅

🚨 real talk, bestie: only use this function when you have other mechanisms guaranteeing that the object won't go away after the RCU read lock is released. like, do not just yeet this and hope the object stays alive. that is not the move. 🙈

it returns the first entry on which the compare function returned true. periodt. ✅

🌈 SEE ALSO 🌈

peep the kernel file ./include/linux/rhashtable.h, plus struct bucket_table(9) and the whole squad:

• struct bucket_table(9)
• rht_grow_above_75(9)
• rht_shrink_below_30(9)
• rht_grow_above_100(9)
• rht_grow_above_max(9)
• rht_for_each_from(9)
• rht_for_each(9)
• rht_for_each_entry_from(9)
• rht_for_each_entry(9)
• rht_for_each_entry_safe(9)
• rht_for_each_rcu_from(9)
• rht_for_each_rcu(9)
• rht_for_each_entry_rcu_from(9)
• rht_for_each_entry_rcu(9)
• rhl_for_each_rcu(9)
• rhl_for_each_entry_rcu(9)
• rhashtable_lookup(9)
• rhltable_lookup(9)
• rhashtable_insert_fast(9)
• rhltable_insert_key(9)
• rhltable_insert(9)
• rhashtable_lookup_insert_fast(9)
• rhashtable_lookup_get_insert_fast(9)
• rhashtable_lookup_insert_key(9)
• rhashtable_lookup_get_insert_key(9)
• rhashtable_remove_fast(9)
• rhltable_remove(9)
• rhashtable_replace_fast(9)
• rhltable_walk_enter(9)
• rhltable_free_and_destroy(9)

source/version: ./include/linux · date: October 2026 · page: rhashtable_lookup_fast(9) — mwah 💋