cpumask_first(9)

💅 cpumask_first(9) — the kernel API manual, bestie edition ✨

Okay so real talk, this page lives in the kernel API manual (section 9, iykyk) and it's about cpumask_first — the tiny little legend that finds you the very first cpu in a cpumask. Yeah. That's it. That's the whole gig. And honestly? She ate. 🎀

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🌸 NAME 🌸

cpumask_first — get the first cpu in a cpumask. literally just the first one, no drama ✨

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🦋 SYNOPSIS 🦋

unsigned int cpumask_first (const struct cpumask *srcp );

copy it exactly like that, spaces and all, bestie — the trailing space before that last paren is part of the vibe 💅

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💖 ARGUMENTS 💖

• srcp — the cpumask pointer. it's the mask you're handing over so she can go find the first cpu in it. that's the whole assignment. 🫶

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✨ RETURN ✨

She gives you back the first cpu. And if there are no cpus set at all? You get something >= nr_cpu_ids — which is your little signal that the mask was empty and there was nothing to find. no cap, that's the check 😭

⚠️ fr fr remember: >= nr_cpu_ids means empty mask, not a real cpu. always vibe-check the return value before you go using it as a cpu id. 💀

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🌈 SEE ALSO 🌈

The whole cpumask friend group showed up, and we're listing every single one of them because we don't do half-messages in this group chat 💜

Specifically: Kernel file ./include/linux/cpumask.h, plus —

• cpumask_pr_args(9), cpumask_first_zero(9), cpumask_first_and(9), cpumask_first_andnot(9), cpumask_first_and_and(9), cpumask_last(9), cpumask_next(9), cpumask_next_zero(9), cpumask_next_and(9), cpumask_next_andnot(9), cpumask_next_and_wrap(9), cpumask_next_wrap(9), cpumask_random(9)
• for_each_cpu(9), for_each_cpu_wrap(9), for_each_cpu_and(9), for_each_cpu_andnot(9), for_each_cpu_or(9), for_each_cpu_from(9)
• cpumask_any_but(9), cpumask_any_and_but(9), cpumask_any_andnot_but(9), cpumask_nth(9), cpumask_nth_and(9), cpumask_nth_and_andnot(9)
• cpumask_set_cpu(9), cpumask_clear_cpus(9), cpumask_clear_cpu(9), cpumask_test_cpu(9), cpumask_test_and_set_cpu(9), cpumask_test_and_clear_cpu(9), cpumask_setall(9), cpumask_clear(9)
• cpumask_and(9), cpumask_or(9), cpumask_weighted_or(9), cpumask_xor(9), cpumask_andnot(9), cpumask_equal(9), cpumask_or_equal(9), cpumask_intersects(9), cpumask_subset(9), cpumask_empty(9), cpumask_full(9), cpumask_weight(9), cpumask_weight_and(9), cpumask_weight_andnot(9), cpumask_shift_right(9), cpumask_shift_left(9), cpumask_copy(9)
• cpumask_any(9), cpumask_any_and(9), cpumask_of(9), cpumask_parse_user(9), cpumask_parselist_user(9), cpumask_parse(9), cpulist_parse(9), cpumask_size(9), alloc_cpumask_var(9), to_cpumask(9), num_online_cpus(9), cpumap_print_bitmask_to_buf(9), cpumap_print_list_to_buf(9)

like… the whole roster. iconic behavior, honestly 👑

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okay that's the whole page, you're officially a cpumask_first understander, go be the main character of your own scheduler 🧚

sign-off szn: this little masterpiece comes from ./include/linux (yes, the directory, she's humble) and it's dated October 2026. 🎀✨🦋