__tty_hangup(9)

💅 __tty_hangup(9) 💅

okay so we're in the Kernel API Manual today bestie, and the star of the show is __tty_hangup — the actual handler for hangup events. like, the real one. the one that does the work. no cap. 🎀

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✨ NAME ✨

__tty_hangup — actual handler for hangup events

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🌸 SYNOPSIS 🌸

void __tty_hangup (struct tty_struct *tty , int exit_session );

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🦋 ARGUMENTS 🦋

• tty — the tty device, obviously. the main character of this whole situation 💅
• exit_session — if this is non-zero, it signals all foreground group processes. like a little ripple effect, iykyk 🌊

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💖 DESCRIPTION 💖

so this one can be called by a "kworker" kernel thread. that's process synchronous but it doesn't hold any locks, which means we gotta make sure we've got the appropriate locks for whatever we're doing. gotta be responsible, bestie 🫶

the hangup event clears any pending redirections onto the hung-up device. it makes sure future writes will error (yes, error — that's the whole point ✨) and it does the needed line discipline hangup and signal delivery. the tty object itself stays intact, so don't worry, nothing's getting deleted out from under you 🌸

🔒 Locking 🔒

bestie, the locking situation is giving main character energy, so pay attention:

• BTM
• redirect lock for undoing redirection
• file list lock for manipulating list of ttys
• tty_ldiscs_lock from called functions
• termios_rwsem resetting termios data
• tasklist_lock to walk task list for hangup event
• ->siglock to protect ->signal/->sighand

fr fr, that's a lot of locks. respect the lock order or the kernel will humble you 💀

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👑 SEE ALSO 👑

Kernel file ./drivers/tty/tty_io.c:

free_tty_struct(9), tty_free_file(9), tty_name(9), get_tty_driver(9), tty_dev_name_to_number(9), tty_find_polling_driver(9), tty_wakeup(9), tty_release_redirect(9), tty_hangup(9), tty_vhangup(9), tty_vhangup_self(9), tty_vhangup_session(9), tty_hung_up_p(9), stop_tty(9), start_tty(9), tty_read(9), tty_write(9), tty_send_xchar(9), pty_line_name(9), tty_line_name(9), tty_driver_lookup_tty(9), tty_init_termios(9), tty_standard_install(9), tty_driver_install_tty(9), tty_driver_remove_tty(9), tty_reopen(9), tty_init_dev(9), tty_save_termios(9), tty_flush_works(9), release_one_tty(9), tty_kref_put(9), release_tty(9), tty_release_checks(9), tty_kclose(9), tty_release_struct(9), tty_release(9), tty_open_current_tty(9), tty_lookup_driver(9), tty_kopen_exclusive(9), tty_kopen_shared(9), tty_open_by_driver(9), tty_open(9), tty_poll(9), tiocsti(9), tiocgwinsz(9), tty_do_resize(9), tiocswinsz(9), tioccons(9), tiocsetd(9), tiocgetd(9), send_break(9), tty_get_tiocm(9), tty_tiocmget(9), tty_tiocmset(9), tty_get_icount(9), alloc_tty_struct(9), tty_put_char(9), tty_register_device(9), tty_register_device_attr(9), tty_unregister_device(9), __tty_alloc_driver(9), tty_driver_kref_put(9), tty_register_driver(9), tty_unregister_driver(9)

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and that's the whole page, bestie 🧚 go forth and hang up those ttys responsibly 💜

later, legend 🎀 — this lil page came from ./drivers/tty and it's dated October 2026 🦋