STRUCT FUTEX_SCHED_DATA(9)

💅 struct futex_sched_data(9) — Kernel API Manual, but make it make sense

okay bestie, so this is struct futex_sched_data(9) — a page straight from the kernel API manual, and it's literally all about the futex related per task data. that's it, that's the vibe. it's a little struct that hangs out per-task and holds all the futex bookkeeping, and we're gonna walk through it together like we're studying for the same exam 🫶

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✨ NAME ✨

struct futex_sched_data — Futex related per task data. no cap, that's the whole name. it's giving "small struct, big responsibilities" 👑

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🦋 SYNOPSIS 🦋

struct futex_sched_data {
    struct robust_list_head __user          *robust_list;
  #ifdef CONFIG_COMPAT;
    struct compat_robust_list_head __user   *compat_robust_list;
  #endif;
    struct list_head                        pi_state_list;
    struct futex_pi_state                   *pi_state_cache;
    struct mutex                            exit_mutex;
    unsigned int                            state;
 };

like, look at her. six-ish fields, one conditional, absolutely main character energy ✨

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🎀 Members 🎀

okay so this is the part where we meet the whole squad, one field at a time 💖

• robust_list — the user space registered robust list pointer. yes, "user space registered" — that pointer lives in userspace and it's registered, and we're just holding onto it here 🌸
• compat_robust_list — the user space registered robust list pointer, but for compat tasks. same deal, different flavour, iykyk 🧚 (and note it only even exists when CONFIG_COMPAT is on, because it's tucked inside that #ifdef, periodt)
• pi_state_list — the list head for Priority Inheritance (PI) state management. yes, that's the actual expansion of PI, spelled out for us, we love a glossary moment 👑
• pi_state_cache — a pointer that caches one PI state object per task. one. per task. lowkey efficient 💅
• exit_mutex — a mutex for serializing exit. it's the bouncer at the door making sure the exits happen one at a time, no chaos 😌
• state — the futex handling state, and its whole job is to handle exit races correctly. very "i'm the one who keeps things from falling apart" of her fr fr 🔥

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🌈 SEE ALSO 🌈

go read these next, bestie, they're all in the same kernel file ./include/linux/futex_types.h:

• struct futex_mm_phash(9)
• struct futex_unlock_cs_range(9)
• struct futex_unlock_cs_ranges(9)
• struct futex_mm_data(9)

like a little futex friend group 🦋✨

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ok that's the whole page, no filler, every field accounted for 💜 now go be obsessed with futexes responsibly.

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and that's a wrap, bestie!! this came to you from ./include/linux, dated October 2026, and it's struct futex_sched_data(9) from the Kernel API Manual — mwah, slay, study hard 🎀💖🌸