cpuset_for_each_child(9)

💅 cpuset_for_each_child — traverse online children of a cpuset

okay bestie, so you know how the kernel API manual has this whole cpuset_for_each_child(9) situation? yeah. we're getting into it. this is the one that walks you through the online children of a cpuset, and honestly it's giving very much "main character energy" for cgroup traversal. let's break it down so you actually get it, no cap.

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✨ SYNOPSIS ✨

cpuset_for_each_child (child_cs , pos_css , parent_cs );

literally the whole vibe in one line. periodt.

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🎀 ARGUMENTS 🎀

• child_cs — this is your loop cursor, and it's pointing at the current child. think of it as your little "where am I right now" bestie. it moves as you iterate, okay? don't lose track of it. 🫶
• pos_css — this one is used for iteration. yeah, that's it. it's the pos helper that keeps the walk going. iconic behavior, honestly. ✨
• parent_cs — the target cpuset whose children you're walking. this is the mom friend of the operation. you're traversing its online children. 🌸

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🦋 DESCRIPTION 🦋

so what does it actually do? it walks child_cs through the online children of parent_cs. that's the whole assignment. no cap.

but here's the thing, and I need you to hear me on this: 🚨 Must be used with RCU read locked. 🚨 like, actually. do not skip that. if you're not holding the RCU read lock, you're not doing it right, and the kernel is not gonna be nice about it. this is a hard requirement, not a suggestion. lock it up before you walk, bestie. 💅

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👑 SEE ALSO 👑

• Kernel file ./kernel/cgroup/cpuset-internal.h — go read it, iykyk. 📖
• cpuset_for_each_descendant_pre(9) — the descendant pre-order version, if you're feeling extra. 🔥

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lowkey reminder: RCU read lock. don't make me say it again. okay I will say it again: RCU read lock. 🙈

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and that's the whole page, bestie! you ate that. slay. 💖

this masterpiece came from ./kernel/cgroup, October 2026, and it's the cpuset_for_each_child(9) manual page — catch you on the next traversal. mwah! 🎀✨