__timer_delete_sync(9)

💅 __timer_delete_sync — the kernel API manual, but make it make sense ✨

okay so bestie, you've stumbled into the kernel's guts and found __timer_delete_sync — that's the internal function, the one behind the curtain, the main character of "please stop, timer, I need you gone and I need you to actually be gone." It deactivates a timer and waits for the handler to finish 🎀

The manual name is __timer_delete_sync(9), by the way — section 9, kernel API manual, iykyk 🦋

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🌸 SYNOPSIS 🌸

int __timer_delete_sync (struct timer_list *timer , bool shutdown );

like, that's the whole vibe. two args, one int return, zero chill 💅

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✨ ARGUMENTS ✨

• timer — the timer you're deactivating. that's the target, the one getting the ✨cancel treatment✨
• shutdown — if it's true, then timer->function gets set to NULL under the timer base lock, which is what stops the timer from being rearmed, no cap 🫶

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🦋 DESCRIPTION 🦋

so here's the tea, and it's actually important tea ☕

If shutdown is not set, the timer can be rearmed later. cute, flexible, whatever. BUT — and this is the part where you gotta pay attention — if the timer can be rearmed concurrently, like after the base lock has been dropped, then the return value is meaningless 😭 like fr fr meaningless. it's giving "don't @ me, i warned you."

If shutdown is set, then timer->function is set to NULL under the timer base lock, and that's what prevents the timer from being rearmed. any attempt to rearm a shutdown timer is silently ignored — like not even a little error, not even a peep, just 💀 nothing. ghosted. periodt.

And if you wanna reuse that timer after shutdown? bestie, you have to initialize it again. no shortcuts, no "it'll probably be fine", it will not probably be fine 🌈

lowkey the whole point: shutdown = permanent, no take-backs, you gotta re-init to bring it back 💜

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👑 RETURN 👑

• 0 — the timer was not pending 🎀
• 1 — the timer was pending and got deactivated, slay ✨

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🔥 SEE ALSO 🔥

oh we're doing the whole friend group, okay, gather round 🫶

The kernel file lives at ./kernel/time/timer.c, and it's hanging out with struct timer_base(9), plus literally everyone else:

• __round_jiffies_relative(9)
• round_jiffies(9)
• round_jiffies_relative(9)
• __round_jiffies_up_relative(9)
• round_jiffies_up(9)
• round_jiffies_up_relative(9)
• timer_init_key(9)
• mod_timer_pending(9)
• mod_timer(9)
• timer_reduce(9)
• add_timer(9)
• add_timer_local(9)
• add_timer_global(9)
• add_timer_on(9)
• __timer_delete(9)
• timer_delete(9)
• timer_shutdown(9)
• __try_to_del_timer_sync(9)
• timer_delete_sync_try(9)
• timer_delete_sync(9)
• timer_shutdown_sync(9)
• fetch_next_timer_interrupt_remote(9)
• timer_unlock_remote_bases(9)
• timer_lock_remote_bases(9)
• timer_base_is_idle(9)
• timer_expire_remote(9)
• get_next_timer_interrupt(9)
• timer_base_try_to_set_idle(9)
• timer_clear_idle(9)
• __run_timers(9)

like okay that's the entire timers extended universe, we love a comprehensive cast 💖

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and that's the whole page, bestie 🧚 this one comes from ./kernel/time, dated October 2026, and it's still filed under __timer_delete_sync(9) — so go forth, delete your timers synchronously, and remember: shutdown means shutdown 💅✨🍓