THR_EXIT(2)

💖 THR_EXIT 💖

okay bestie, so this one is from the System Calls Manual section — it's thr_exit, and it's giving "terminate current thread" energy. let's get into it 🦋

✨ NAME ✨

thr_exit — terminate current thread 💅

📚 LIBRARY 📚

Standard C Library — that's libc, linked with -lc. yep, she's a libc girlie 🎀

🌸 SYNOPSIS 🌸

#include <sys/thr.h>

void
thr_exit(long *state);

🫶 DESCRIPTION 🫶

okay so real talk: this function is literally intended for implementing threading. if you're just a normal application doing normal application things, you should be calling pthread_exit(3) instead. no cap. thr_exit is the low-level machinery, not the vibe you want to be messing with unless you're literally building a threading library 💀

The thr_exit() system call terminates the current kernel-scheduled thread. periodt.

Now, if the state argument is not NULL, the location that the argument points to gets updated with an arbitrary non-zero value, and an _umtx_op(2) UMTX_OP_WAKE operation is consequently performed on that location. (yes bestie, arbitrary — don't go assuming it's your thread id or anything cute like that, it's just... a non-zero value. it is what it is 🙈)

⚠️ big warning energy: attempts to terminate the last thread in the process are silently ignored. like, no error, no nothing, just vibes and a shrug. if you actually want the process gone-gone, use the _exit(2) syscall to terminate the process. that's the move 👑

⭐ RETURN VALUES ⭐

The function does not return a value. that's the whole point, she exits.

but lowkey, if you do see a return from this function? that means the calling thread was the last one in the process. so like... if you get a return, that's your sign. main character moment, but also kind of a jumpscare 😭

👀 SEE ALSO 👀

• _exit(2)
• thr_kill(2)
• thr_kill2(2)
• thr_new(2)
• thr_self(2)
• thr_set_name(2)
• _umtx_op(2)
• pthread_exit(3)

🌈 STANDARDS 🌈

The thr_exit() system call is non-standard — she's not in any official spec, she's just doing her own thing. she's used by the 1:1 Threading Library (libthr, -lthr) to implement the IEEE Std 1003.1-2001 (“POSIX.1”) pthread(3) functionality. so like, the posix girlies are standing on her shoulders, iykyk 💅

and that's the whole page bestie!! this one shipped from Debian on June 1, 2016 — yeah she's an oldie but a goodie, and she's still out here holding up your threads. slay, queen. go call pthread_exit(3) like a normal person tho 🎀✨🦋💖