try_to_wake_up(9)

💅 try_to_wake_up(9) — like, the whole vibe

okay bestie, gather 'round, because this is the try_to_wake_up(9) page from the Kernel API Manual and it's literally about waking up a thread 💤➡️✨ no cap.

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🌸 NAME 🌸

try_to_wake_up — wake up a thread 🫶

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✨ SYNOPSIS ✨

int try_to_wake_up (struct task_struct *p , unsigned int state , int
       wake_flags );

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🎀 ARGUMENTS 🎀

• p — the thread to be awakened, like the main character finally getting out of bed 😭
• state — the mask of task states that can be woken 🎭
• wake_flags — wake modifier flags (WF_*) 🚩

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💖 DESCRIPTION 💖

So conceptually, this function does this:

If (state & p->state) p->state = TASK_RUNNING.

And if the task was not queued/runnable, it also places it back on a runqueue. periodt. 👑

This function is atomic against schedule which would dequeue the task. iykyk.

It issues a full memory barrier before accessing p->state, see the comment with set_current_state. memory barriers are like, the bouncers of the kernel, fr fr 🧚

Uses p->pi_lock to serialize against concurrent wake-ups. no racing allowed bestie 🙅‍♀️

Relies on p->pi_lock stabilizing:

• p->sched_class
• p->cpus_ptr
• p->sched_task_group in order to do migration, see its use of select_task_rq/set_task_cpu.

Tries really hard to only take one task_rq(p)->lock for performance 🔥 like it's genuinely doing its best. Takes rq->lock in:

• ttwu_runnable — old rq, unavoidable, see comment there;
• ttwu_queue — new rq, for enqueue of the task;
• psi_ttwu_dequeue — much sadness :-( accounting will kill us. 💀

As a consequence we race really badly with just about everything. See the many memory barriers and their comments for details. like it's giving chaos but make it ✨documented✨

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⭐ RETURN ⭐

true if p->state changes (an actual wakeup was done), false otherwise. slay 💅

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🦋 SEE ALSO 🦋

Kernel file ./kernel/sched/core.c plus these iconic functions:

• wake_q_add(9)
• wake_q_add_safe(9)
• task_curr(9)
• task_call_func(9)
• cpu_curr_snapshot(9)
• wake_up_process(9)
• preempt_notifier_register(9)
• preempt_notifier_unregister(9)
• prepare_task_switch(9)
• finish_task_switch(9)
• 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 whole page bestie 🫶 go wake up some threads responsibly 💜

okay bye, this was ./kernel/sched from October 2026, try_to_wake_up(9) — catch you in the group chat 🌈💅