prepare_task_switch(9)

💅 prepare_task_switch(9) — like, the official kernel API manual, bestie ✨

Okay so real talk: this is a page from the Kernel API Manual and it's all about prepare_task_switch — the little pre-game ritual the scheduler does before it hands the CPU to somebody else. It's short, it's iconic, and it's load-bearing, so pay attention 🫶

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✨ SYNOPSIS ✨

void prepare_task_switch (struct rq *rq , struct task_struct *prev ,
       struct task_struct *next );

That's the whole thing. Returns void. No notes. No drama. Just vibes and a context switch incoming 🦋

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🎀 ARGUMENTS 🎀

• rq — the runqueue that's getting ready to do the switch. It's the one throwing the party 💅
• prev — the current task, aka the one being switched out. It's leaving the group chat 😭
• next — the task we're going to switch to. Main character energy, arriving now 👑

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🔥 DESCRIPTION 🔥

So here's the tea: this gets called with the rq lock held and interrupts off. That's not optional, that's the whole deal, no cap.

It must be paired with a subsequent finish_task_switch after the context switch. Like, they're a matching set. Separating them is giving "unfinished business" and we don't do that here 🙈

What it actually does: prepare_task_switch sets up locking and calls architecture specific hooks. Architecture specific. Like, the arch code gets to do its own little thing. Slay ✨

⚠️ Genuine caution, bestie: rq lock held, interrupts off. Do not show up to this function unprepared. It is not a "figure it out as you go" situation 💀

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🌈 SEE ALSO 🌈

Kernel file ./kernel/sched/core.c — and like, a whole friend group of related functions:

• wake_q_add(9)
• wake_q_add_safe(9)
• task_curr(9)
• try_to_wake_up(9)
• task_call_func(9)
• cpu_curr_snapshot(9)
• wake_up_process(9)
• preempt_notifier_register(9)
• preempt_notifier_unregister(9)
• finish_task_switch(9) — the bestie, obviously 💖
• schedule_tail(9)
• schedule_preempt_disabled(9)
• preempt_schedule_notrace(9)
• init_idle(9)
• curr_task(9)

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And that's the page, periodt 🎀 Huge thanks to ./kernel/sched for keeping the receipts — this one's from the October 2026 release of the Kernel API Manual. Go forth and switch tasks responsibly, babe 🧚💜