clocksource_...spend_timing(9)

✨ clocksource_...spend_timing(9) — a Kernel API Manual moment ✨

okay bestie, buckle up, because we're diving into the Kernel API Manual and this one is a lil function with a big job 🎀 it's called clocksource_start_suspend_timing, and honestly? it's giving "quiet hero of the suspend arc."

---

🌸 NAME 🌸

clocksource_start_suspend_timing — literally just starts measuring the suspend timing 💅 that's it, that's the whole vibe.

---

🦋 SYNOPSIS 🦋

void clocksource_start_suspend_timing (struct clocksource *cs , u64
start_cycles );

no cap, that's the whole signature 🫶

---

🎀 ARGUMENTS 🎀

• cs — the current clocksource from timekeeping. yes queen, the one timekeeping is using right now ✨
• start_cycles — the current cycles from timekeeping. this is the starting number we're gonna hold onto 🍓

---

💖 DESCRIPTION 💖

so what does this actually do? bestie, it saves the start cycle values of the suspend timer so that when the system resumes, we can calculate the suspend time 😭 like a little "we left at 3:47pm" sticky note for your kernel. iconic behavior honestly.

and the timing of when it gets called is so specific — it's called late in the suspend process, from timekeeping_suspend. by that point processes are frozen, non-boot cpus and interrupts are disabled. so everything is quiet, everything is chill, nobody's touching anything 🙈

and because of that whole frozen situation, it's therefore possible to start the suspend timer without taking the clocksource mutex 👑 and that's the whole reason this works the way it works. main character energy.

---

💜 SEE ALSO 💜

this function does not roll alone, bestie — here's the whole friend group from the kernel file ./kernel/time/clocksource.c:

• clocks_calc_mult_shift(9)
• clocksource_mark_unstable(9)
• clocksource_suspend_select(9)
• clocksource_stop_suspend_timing(9)
• clocksource_suspend(9)
• clocksource_resume(9)
• clocksource_touch_watchdog(9)
• clocksource_max_adjustment(9)
• clocks_calc_max_nsecs(9)
• clocksource_update_max_deferment(9)
• clocksource_select(9)
• __clocksource_update_freq_scale(9)
• __clocksource_register_scale(9)
• clocksource_unregister(9)
• current_clocksource_show(9)
• current_clocksource_store(9)
• unbind_clocksource_store(9)
• available_clocksource_show(9)
• boot_override_clocksource(9)
• boot_override_clock(9)

---

lowkey the whole clocksource squad is here. iykyk 🌈

---

and that's the page, bestie! 🧚 this lil gem lives in ./kernel/time, dated October 2026, cheerfully stamped with the Kernel API Manual name up top 💅✨ go forth and measure your suspend timing, periodt. 🎀💖