queued_spin_lock_slowpath(9)

💅 queued_spin_lock_slowpath(9) 💅

okay bestie, so this one's a Kernel API Manual page and honestly? it's giving "the moment the fast path gives up and hands the mic to the slow path." let's get into it 🎀

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✨ NAME ✨

queued_spin_lock_slowpath — acquire the queued spinlock 🔒

like, the slow way. no cap, sometimes you just gotta queue up.

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🦋 SYNOPSIS 🦋

void __lockfunc queued_spin_lock_slowpath (struct qspinlock *lock , u32
val );

that's the whole signature, literally. void, __lockfunc, and two args. slay.

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🌸 ARGUMENTS 🌸

• lock — Pointer to queued spinlock structure. yes bestie, this is the lock, the one you're fighting for 👑
• val — Current value of the queued spinlock 32-bit word. it's a u32, it's the current state of the word, okay? iykyk 💜

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🌈 DESCRIPTION 🌈

okay so the first thing you need to internalize is the legend:

       (queue tail, pending bit, lock value)

that's the vibe check for the entire diagram below: every state is written as (queue tail, pending bit, lock value). memorize that and the rest is a whole mood 🧚

and here's the state machine, verbatim, because i am not about to redraw ASCII art that beautiful:

       (queue tail, pending bit, lock value)

       fast     :    slow                                  :    unlock :
       : uncontended  (0,0,0) -:--> (0,0,1) ------------------------------:-->
       (*,*,0) :       | ^--------.------.             /  : :       v
                         |  : pending               :    (0,1,1) +--> (0,1,0)
                  |  : :       | ^--'              |           |  : :       v
       |           |  : uncontended           :    (n,x,y) +--> (n,0,0) --'
       |  : queue               :       | ^--'                          |  : :
       v                               |  : contended             :    (*,x,y)
       +--> (*,0,0) ---> (*,0,1) -'  : queue               :         ^--'
       :

three lanes, bestie: fast, slow, unlock. the fast lane starts uncontended at (0,0,0), the slow lane does the queue-and-pending thing, and unlock is the one that actually lets people out. it's giving main character energy all around 💫

fr fr stare at that diagram for a sec before you touch the code. it's the whole page. 🫶

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⭐ SEE ALSO ⭐

• Kernel file ./kernel/locking/qspinlock.c — go read it, that's where the actual tea is ☕

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and that's the whole page, no notes 💅 tiny sign-off from your girl: this one lives in ./kernel/locking, it's dated October 2026, and the footer spells it all out as queued_spin_lock_slowpath(9) 🎀✨💖