list_for_eac...try_lockless(9)

💅 list_for_each_entry_lockless(9) — like, the lockless list vibe 🦋

okay bestie, so this is a page straight out of the Kernel API Manual, section 9, and the page is literally called list_for_eac...try_lockless(9) (yes the title got truncated in the header, no that's not a typo on my part, it's just giving terminal-width energy 💀). anyway. sit down, grab a boba, we're looping over lists today. ✨

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🌸 NAME 🌸

list_for_each_entry_lockless — iterate over rcu list of given type

periodt. that's the whole name section. iconic brevity.

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✨ SYNOPSIS ✨

list_for_each_entry_lockless (pos , head , member );

not me putting it in a code block so your eyes don't glaze over 🫶 copy it exactly, the spacing is canon.

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🎀 ARGUMENTS 🎀

three args, three chances to mess it up, let's go:

• pos — the type * to use as a loop cursor. literally your main character variable, she walks the list for you 💅
• head — the head for your list. the starting point, the home base, the group chat admin 🌈
• member — the name of the list_struct within the struct. telling the macro which field inside your struct is the actual list node, iykyk 🧚

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💖 DESCRIPTION 💖

so here's the tea: this primitive may safely run concurrently with the _rcu list-mutation primitives such as list_add_rcu, but — and this is the important part, don't scroll past it — it requires some implicit RCU read-side guarding. 🫶

"implicit" meaning you don't see it, but it lowkey has to be there. it's giving "trust me bro" but in a kernel-legal way.

two examples the page gives for when that's chill:

1. running within a special exception-time environment where preemption is disabled and where lockdep cannot be invoked 🔥
2. when items are added to the list, but never deleted — nothing leaves, so nothing can bite you on the way out 🦋

bestie warning: "implicit RCU read-side guarding" is doing a LOT of heavy lifting in that sentence. if neither of those two situations describes what you're doing, do not just vibe-check your way into using this. 😭

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👑 SEE ALSO 👑

the page points you at the kernel file ./include/linux/rculist.h, and then proceeds to dump the entire friend group. not me listing all of them, but like — all of them. no skipping, we don't do that here 💜

• list_for_each_rcu(9)
• list_tail_rcu(9)
• list_add_rcu(9)
• list_add_tail_rcu(9)
• list_del_rcu(9)
• list_bidir_del_rcu(9)
• hlist_del_init_rcu(9)
• list_replace_rcu(9)
• list_splice_rcu(9)
• __list_splice_init_rcu(9)
• list_splice_init_rcu(9)
• list_splice_tail_init_rcu(9)
• list_entry_rcu(9)
• list_first_or_null_rcu(9)
• list_next_or_null_rcu(9)
• list_for_each_entry_rcu(9)
• list_for_each_entry_srcu(9)
• list_entry_lockless(9)
• list_for_each_entry_continue_rcu(9)
• list_for_each_entry_from_rcu(9)
• hlist_del_rcu(9)
• hlist_replace_rcu(9)
• hlists_swap_heads_rcu(9)
• hlist_add_head_rcu(9)
• hlist_add_tail_rcu(9)
• hlist_add_before_rcu(9)
• hlist_add_behind_rcu(9)
• hlist_for_each_entry_rcu(9)
• hlist_for_each_entry_srcu(9)
• hlist_for_each_entry_rcu_notrace(9)
• hlist_for_each_entry_rcu_bh(9)
• hlist_for_each_entry_continue_rcu(9)
• hlist_for_each_entry_continue_rcu_bh(9)
• hlist_for_each_entry_from_rcu(9)

and yeah, list_entry_lockless(9) right there in the middle is basically this page's sibling, go say hi 🍓

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okay that's the whole thing, you ate that 💅

this little love letter came to you from ./include/linux, dated October 2026, and the footer's version line is literally list_for_eac...try_lockless(9) again — the header and footer are matching, that's called commitment, we stan a consistent layout. mwah. 💖✨🎀