rht_for_each_rcu_from(9)

✨ rht_for_each_rcu_from ✨

okay bestie, so this is a page from the Kernel API Manual and it's literally about rht_for_each_rcu_from(9) — a macro that walks an RCU hash chain starting from a head you pick. it's giving "loop cursor era" and honestly? iconic. 🎀

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🌸 SYNOPSIS 🌸

rht_for_each_rcu_from (pos , head , tbl , hash );

like, that's the whole call. four things in, vibe check complete. 💅

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🦋 ARGUMENTS 🦋

• pos — the struct rhash_head you're using as your loop cursor. she's the main character that moves down the chain, keep an eye on her 👀
• head — the struct rhash_head you start from. your launch point, your origin story, your "we begin here" ✨
• tbl — the struct bucket_table. the whole bucket situation this chain lives in 🪣
• hash — the hash value / bucket index. which bucket we're in, no cap 🔢

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💖 DESCRIPTION 💖

okay so this is a hash chain list-traversal primitive, and here's the important part: it may safely run concurrently with the _rcu mutation primitives — like rhashtable_insert — as long as the traversal is guarded by rcu_read_lock. 🫶

not me stressing the rcu_read_lock part — girl, do NOT skip the guard, that's the whole deal 💀

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🌈 SEE ALSO 🌈

so many siblings, she's from a big family fr fr:

• Kernel file ./include/linux/rhashtable.h 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(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)
• rhashtable_lookup_fast(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)

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and that's the page, bestie! 🧚 this lil drop came straight out of ./include/linux and it's stamped October 2026 — so yeah, rht_for_each_rcu_from(9), see you in the kernel 💜🔥