sync_clear_bit(9)

💅 sync_clear_bit — a.k.a. the Kernel API Manual moment

okay so bestie, welcome to sync_clear_bit(9), straight out of the Kernel API Manual ✨ this one's a tiny little function with a big main-character job: it clears a bit in memory. that's it. that's the vibe. let's get into it 🎀

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✨ NAME ✨

sync_clear_bit — Clears a bit in memory 🧹💫

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🌸 SYNOPSIS 🌸

void sync_clear_bit (long nr , volatile unsigned long *addr );

like, look at her. so short. so iconic. 👑

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🦋 ARGUMENTS 🦋

• nr — the bit you're clearing, bestie 🎯 that's the one getting yeeted to zero.
• addr — the address you start counting from 🗺️ like, where the counting begins, fr fr.

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💜 DESCRIPTION 💜

so here's the tea 🍓: sync_clear_bit is atomic and may not be reordered. no cap, it's locked in like that. 💅

BUT — and this is the important part, don't skip it — it does not contain a memory barrier 😭 so if you're out here using it for locking purposes, you should call smp_mb__before_atomic and/or smp_mb__after_atomic in order to ensure changes are visible on other processors. that's the whole deal, iykyk 🫶

lowkey do not forget the barrier calls if you're locking, bestie. the function will not do it for you and that's on periodt 💀

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🔥 SEE ALSO 🔥

• Kernel file ./arch/x86/include/asm/sync_bitops.h 📁
• sync_set_bit(9)
• sync_change_bit(9)
• sync_test_and_set_bit(9)
• sync_test_and_clear_bit(9)
• sync_test_and_change_bit(9)

the whole sync_bitops friend group, honestly. go say hi 🌈

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okay that's the page!! mwah 💋 this lil cutie lives in ./arch/x86/include/asm, dated October 2026, and she's filed under sync_clear_bit(9) — go clear some bits for me, bestie, and slay responsibly 👑💖✨