clocksource_mark_unstable(9)

💅 clocksource_mark_unstable — bestie edition ✨

okay so like, we're in the Kernel API Manual today, and this page is clocksource_mark_unstable(9). yes the name is a mouthful, no we're not changing it, it's iconic. 🫶

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✨ NAME ✨

clocksource_mark_unstable — mark a clocksource as unstable, courtesy of the watchdog 🐕

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🌸 SYNOPSIS 🌸

void clocksource_mark_unstable (struct clocksource *cs );

like, that's it. that's the whole vibe. void return, one argument, no drama. 💅

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🎀 ARGUMENTS 🎀

• cs — the clocksource that's about to get marked unstable. not a guess at a clocksource, the actual struct clocksource * bestie. this is the one getting the ✨not like the other girls✨ treatment.

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🦋 DESCRIPTION 🦋

okay so here's the tea 🍵 — this function gets called by the x86 TSC code to mark clocksources as unstable. it's giving "the bouncer at the club checking IDs" energy.

and the important part: it does not do the demotion and re-selection work right then and there. nope. it defers all of that to a kthread. so the function just kind of… flags the situation and dips 🙈, letting the kthread handle the actual messy admin later. delegation icon! 👑

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💜 SEE ALSO 💜

ok so this function does not exist in a vacuum, bestie, there's a whole squad in the kernel file ./kernel/time/clocksource.c and here's the full roster, no one gets left behind:

• clocks_calc_mult_shift(9)
• clocksource_suspend_select(9)
• clocksource_start_suspend_timing(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)

literally the whole group chat 💖

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and that's the page! 🎉 this lil drop came to you from ./kernel/time, dated October 2026, and it's called clocksource_mark_unstable(9) in case you already forgot (you didn't, you ate that). mwah 💋✨ stay stable-ish, bestie 🌈