atomic_long_xchg(9)

💅 atomic_long_xchg(9) 💅

okay bestie, quick vibe check before we dive in: this is atomic_long_xchg(9) from the Kernel API Manual, and honestly? she's a short page but she's a potent page. one atomically-ordered little swap and your day is made. let's get into it 🫶

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🌸 NAME 🌸

atomic_long_xchg — atomic exchange with full ordering. yes, the whole point: swap the value and make sure everyone else sees it in the right order. periodt. 🔥

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✨ SYNOPSIS ✨

long atomic_long_xchg (atomic_long_t *v , long new );

that's the whole signature, no cap. drop it in and go 🎀

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🎀 ARGUMENTS 🎀

• v — pointer to an atomic_long_t. that's the thing getting swapped, she's the main character here 👑
• new — a long value to assign. this is what lands in v ✨

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💖 DESCRIPTION 💖

so here's the tea ☕: atomic_long_xchg atomically updates v to new with full ordering. the way that it just... does the whole swap in one go, no half-steps, no peeking? iconic. the ordering is full, so nobody's reordering you around behind your back, iykyk 💅

⚠️ okay this part is important and i need you to actually read it: it is unsafe to use in noinstr code. use raw_atomic_long_xchg there instead. like, do not do the thing. please. 😭

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🦋 RETURN 🦋

returns the original value of v — the one that was there before you swapped it out. it's giving "here's what you had, don't lose it" 🍓

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👑 SEE ALSO 👑

bestie there are SO many siblings, i need you to sit down lol. these all live in the kernel file ./include/linux/atomic/atomic-instrumented.h — a whole family reunion 🌈

starting with the atomic_ girlies:

atomic_read(9), atomic_read_acquire(9), atomic_set(9), atomic_set_release(9), atomic_add(9), atomic_add_return(9), atomic_add_return_acquire(9), atomic_add_return_release(9), atomic_add_return_relaxed(9), atomic_fetch_add(9), atomic_fetch_add_acquire(9), atomic_fetch_add_release(9), atomic_fetch_add_relaxed(9), atomic_sub(9), atomic_sub_return(9), atomic_sub_return_acquire(9), atomic_sub_return_release(9), atomic_sub_return_relaxed(9), atomic_fetch_sub(9), atomic_fetch_sub_acquire(9), atomic_fetch_sub_release(9), atomic_fetch_sub_relaxed(9), atomic_inc(9), atomic_inc_return(9), atomic_inc_return_acquire(9), atomic_inc_return_release(9), atomic_inc_return_relaxed(9), atomic_fetch_inc(9), atomic_fetch_inc_acquire(9), atomic_fetch_inc_release(9), atomic_fetch_inc_relaxed(9), atomic_dec(9), atomic_dec_return(9), atomic_dec_return_acquire(9), atomic_dec_return_release(9), atomic_dec_return_relaxed(9), atomic_fetch_dec(9), atomic_fetch_dec_acquire(9), atomic_fetch_dec_release(9), atomic_fetch_dec_relaxed(9), atomic_and(9), atomic_fetch_and(9), atomic_fetch_and_acquire(9), atomic_fetch_and_release(9), atomic_fetch_and_relaxed(9), atomic_andnot(9), atomic_fetch_andnot(9), atomic_fetch_andnot_acquire(9), atomic_fetch_andnot_release(9), atomic_fetch_andnot_relaxed(9), atomic_or(9), atomic_fetch_or(9), atomic_fetch_or_acquire(9), atomic_fetch_or_release(9), atomic_fetch_or_relaxed(9), atomic_xor(9), atomic_fetch_xor(9), atomic_fetch_xor_acquire(9), atomic_fetch_xor_release(9), atomic_fetch_xor_relaxed(9), atomic_xchg(9), atomic_xchg_acquire(9), atomic_xchg_release(9), atomic_xchg_relaxed(9), atomic_cmpxchg(9), atomic_cmpxchg_acquire(9), atomic_cmpxchg_release(9), atomic_cmpxchg_relaxed(9), atomic_try_cmpxchg(9), atomic_try_cmpxchg_acquire(9), atomic_try_cmpxchg_release(9), atomic_try_cmpxchg_relaxed(9), atomic_sub_and_test(9), atomic_dec_and_test(9), atomic_inc_and_test(9), atomic_add_negative(9), atomic_add_negative_acquire(9), atomic_add_negative_release(9), atomic_add_negative_relaxed(9), atomic_fetch_add_unless(9), atomic_add_unless(9), atomic_inc_not_zero(9), atomic_inc_unless_negative(9), atomic_dec_unless_positive(9), atomic_dec_if_positive(9),

then the atomic64_ crew rolls up (they ate, honestly):

atomic64_read(9), atomic64_read_acquire(9), atomic64_set(9), atomic64_set_release(9), atomic64_add(9), atomic64_add_return(9), atomic64_add_return_acquire(9), atomic64_add_return_release(9), atomic64_add_return_relaxed(9), atomic64_fetch_add(9), atomic64_fetch_add_acquire(9), atomic64_fetch_add_release(9), atomic64_fetch_add_relaxed(9), atomic64_sub(9), atomic64_sub_return(9), atomic64_sub_return_acquire(9), atomic64_sub_return_release(9), atomic64_sub_return_relaxed(9), atomic64_fetch_sub(9), atomic64_fetch_sub_acquire(9), atomic64_fetch_sub_release(9), atomic64_fetch_sub_relaxed(9), atomic64_inc(9), atomic64_inc_return(9), atomic64_inc_return_acquire(9), atomic64_inc_return_release(9), atomic64_inc_return_relaxed(9), atomic64_fetch_inc(9), atomic64_fetch_inc_acquire(9), atomic64_fetch_inc_release(9), atomic64_fetch_inc_relaxed(9), atomic64_dec(9), atomic64_dec_return(9), atomic64_dec_return_acquire(9), atomic64_dec_return_release(9), atomic64_dec_return_relaxed(9), atomic64_fetch_dec(9), atomic64_fetch_dec_acquire(9), atomic64_fetch_dec_release(9), atomic64_fetch_dec_relaxed(9), atomic64_and(9), atomic64_fetch_and(9), atomic64_fetch_and_acquire(9), atomic64_fetch_and_release(9), atomic64_fetch_and_relaxed(9), atomic64_andnot(9), atomic64_fetch_andnot(9), atomic64_fetch_andnot_acquire(9), atomic64_fetch_andnot_release(9), atomic64_fetch_andnot_relaxed(9), atomic64_or(9), atomic64_fetch_or(9), atomic64_fetch_or_acquire(9), atomic64_fetch_or_release(9), atomic64_fetch_or_relaxed(9), atomic64_xor(9), atomic64_fetch_xor(9), atomic64_fetch_xor_acquire(9), atomic64_fetch_xor_release(9), atomic64_fetch_xor_relaxed(9), atomic64_xchg(9), atomic64_xchg_acquire(9), atomic64_xchg_release(9), atomic64_xchg_relaxed(9), atomic64_cmpxchg(9), atomic64_cmpxchg_acquire(9), atomic64_cmpxchg_release(9), atomic64_cmpxchg_relaxed(9), atomic64_try_cmpxchg(9), atomic64_try_cmpxchg_acquire(9), atomic64_try_cmpxchg_release(9), atomic64_try_cmpxchg_relaxed(9), atomic64_sub_and_test(9), atomic64_dec_and_test(9), atomic64_inc_and_test(9), atomic64_add_negative(9), atomic64_add_negative_acquire(9), atomic64_add_negative_release(9), atomic64_add_negative_relaxed(9), atomic64_fetch_add_unless(9), atomic64_add_unless(9), atomic64_inc_not_zero(9), atomic64_inc_unless_negative(9), atomic64_dec_unless_positive(9), atomic64_dec_if_positive(9),

and finally our own atomic_long_ extended fam — note that atomic_long_xchg itself is on this page, so bestie doesn't get a link, she's the host 💖:

atomic_long_read(9), atomic_long_read_acquire(9), atomic_long_set(9), atomic_long_set_release(9), atomic_long_add(9), atomic_long_add_return(9), atomic_long_add_return_acquire(9), atomic_long_add_return_release(9), atomic_long_add_return_relaxed(9), atomic_long_fetch_add(9), atomic_long_fetch_add_acquire(9), atomic_long_fetch_add_release(9), atomic_long_fetch_add_relaxed(9), atomic_long_sub(9), atomic_long_sub_return(9), atomic_long_sub_return_acquire(9), atomic_long_sub_return_release(9), atomic_long_sub_return_relaxed(9), atomic_long_fetch_sub(9), atomic_long_fetch_sub_acquire(9), atomic_long_fetch_sub_release(9), atomic_long_fetch_sub_relaxed(9), atomic_long_inc(9), atomic_long_inc_return(9), atomic_long_inc_return_acquire(9), atomic_long_inc_return_release(9), atomic_long_inc_return_relaxed(9), atomic_long_fetch_inc(9), atomic_long_fetch_inc_acquire(9), atomic_long_fetch_inc_release(9), atomic_long_fetch_inc_relaxed(9), atomic_long_dec(9), atomic_long_dec_return(9), atomic_long_dec_return_acquire(9), atomic_long_dec_return_release(9), atomic_long_dec_return_relaxed(9), atomic_long_fetch_dec(9), atomic_long_fetch_dec_acquire(9), atomic_long_fetch_dec_release(9), atomic_long_fetch_dec_relaxed(9), atomic_long_and(9), atomic_long_fetch_and(9), atomic_long_fetch_and_acquire(9), atomic_long_fetch_and_release(9), atomic_long_fetch_and_relaxed(9), atomic_long_andnot(9), atomic_long_fetch_andnot(9), atomic_long_fetch_andnot_acquire(9), atomic_long_fetch_andnot_release(9), atomic_long_fetch_andnot_relaxed(9), atomic_long_or(9), atomic_long_fetch_or(9), atomic_long_fetch_or_acquire(9), atomic_long_fetch_or_release(9), atomic_long_fetch_or_relaxed(9), atomic_long_xor(9), atomic_long_fetch_xor(9), atomic_long_fetch_xor_acquire(9), atomic_long_fetch_xor_release(9), atomic_long_fetch_xor_relaxed(9), atomic_long_xchg_acquire(9), atomic_long_xchg_release(9), atomic_long_xchg_relaxed(9), atomic_long_cmpxchg(9), atomic_long_cmpxchg_acquire(9), atomic_long_cmpxchg_release(9), atomic_long_cmpxchg_relaxed(9), atomic_long_try_cmpxchg(9), atomic_long_try_cmpxchg_acquire(9), atomic_long_try_cmpxchg_release(9), atomic_long_try_cmpxchg_relaxed(9), atomic_long_sub_and_test(9), atomic_long_dec_and_test(9), atomic_long_inc_and_test(9), atomic_long_add_negative(9), atomic_long_add_negative_acquire(9), atomic_long_add_negative_release(9), atomic_long_add_negative_relaxed(9), atomic_long_fetch_add_unless(9), atomic_long_add_unless(9), atomic_long_inc_not_zero(9), atomic_long_inc_unless_negative(9), atomic_long_dec_unless_positive(9), atomic_long_dec_if_positive(9)

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that's the whole page bb 🧚 go be atomic, stay ordered, and remember: noinstr code gets raw_atomic_long_xchg, not this one 🫶

source file: ./include/linux/atomic · dated October 2026 · filed under atomic_long_xchg(9) in your Kernel API Manual, mwah 💋