do_smart_update(9)

📦 version 7.3.1, in nixpkgs unstable

💅 do_smart_update(9)

okay so real talk, this is a page from the Kernel API Manual (the do_smart_update one, yes bestie, section 9) and it's honestly kind of iconic — it's the optimized version of update_queue and it does exactly as much work as it needs to and not a single syscall more. main character energy fr fr 🎀

✨ NAME ✨

do_smart_update — the optimized update_queue, slay 💅

🦋 SYNOPSIS 🦋

void do_smart_update (struct sem_array *sma , struct sembuf *sops , int
nsops , int otime , struct wake_q_head *wake_q );

like, look at that signature. gorgeous. no notes. ⭐

🌸 ARGUMENTS 🌸

  • sma — the semaphore array 💖 (the whole vibe of this function revolves around it)
  • sops — the operations that were actually performed ✨ (past tense, bestie, they already happened)
  • nsops — the number of operations 🫶 (count 'em)
  • otime — force setting otime 👑 (yes, force — it's giving assertive)
  • wake_q — the lockless wake-queue head 🧚 (lockless!! we love a low-contention queen)

🔥 DESCRIPTION 🔥

okay so here's the tea: do_smart_update does the required calls to update_queue and wakeup_zero, based on the actual changes that were performed on the semaphore array. like, it's smart about it — hence the name, iykyk 😌

⚠️ but listen — the function does not do the actual wake-up. not me being responsible for my own callbacks 🙈 the caller is responsible for calling wake_up_q. it is safe to perform this call after dropping all locks, though, which is genuinely such a relief. 🫶

🌈 SEE ALSO 🌈

Kernel file ./ipc/sem.c, plus the whole friend group:

💜 and that's the page!! this little icon lives over in ./ipc, dropping in October 2026 — mwah, periodt, no cap, go read update_queue(9) next if you're obsessed with me 🎀✨

📦 where this page comes from