PTHREAD_RWLOCK_INIT(3)

📦 version 15.1, in freebsd 14.5, freebsd 15.1, nixpkgs unstable

💖 NAME 💖

okay bestie, welcome to the PTHREAD_RWLOCK_INIT(3) page — yes, that's the actual manual name, and we're in section 3 today 💅 The whole vibe: pthread_rwlock_init initializes a read/write lock. Iconic little setup function, fr fr.

🦋 LIBRARY 🦋

POSIX Threads Library (libpthread, -lpthread) — that's the crew you're linking against, no cap.

✨ SYNOPSIS ✨

#include <pthread.h>

int
pthread_rwlock_init(pthread_rwlock_t *restrict lock,
    const pthread_rwlockattr_t *restrict attr);

🌸 DESCRIPTION 🌸

The pthread_rwlock_init() function is used to initialize a read/write lock, with attributes specified by attr. The way that this works is very main-character: you hand it a lock and some attributes, and it sets the lock up for you.

If attr is NULL, the default read/write lock attributes are used. Very "just go with the defaults, bestie" energy 💅

🚨 Undefined behavior alert: the results of calling pthread_rwlock_init() with an already initialized lock are undefined. Like, not "oops, cute little error" undefined — actually undefined. Do not re-init a lock that's already live. Periodt. 💀

🎀 RETURN VALUES 🎀

If successful, the pthread_rwlock_init() function will return zero. Otherwise an error number will be returned to indicate the error. That's it — zero means slay, nonzero means read the next section 🔥

🫶 ERRORS 🫶

The pthread_rwlock_init() function will fail if:

  • [EAGAIN] — The system lacked the necessary resources (other than memory) to initialize the lock.
  • [ENOMEM] — Insufficient memory exists to initialize the lock.
  • [EPERM] — The caller does not have sufficient privilege to perform the operation.

The pthread_rwlock_init() function may fail if:

  • [EBUSY] — The system has detected an attempt to re-initialize the object referenced by lock, a previously initialized but not yet destroyed read/write lock.
  • [EINVAL] — The value specified by attr is invalid.
🙈 lowkey important: [EBUSY] is the "bestie, you already initialized this lock and haven't destroyed it yet" situation. Do not pass go, do not collect $200.

🌈 SEE ALSO 🌈

⭐ STANDARDS ⭐

The pthread_rwlock_init() function is expected to conform to Version 2 of the Single UNIX Specification (“SUSv2”). So yes, it's giving standards-compliant 👑

🧚 HISTORY 🧚

The pthread_rwlock_init() function first appeared in FreeBSD 3.0. Vintage but still relevant, iykyk 🦋

mwah 💋 — this page is from the Debian crew, dated August 17, 2018, and it's literally the PTHREAD_RWLOCK_INIT(3) manual page. byeee 🫶💜

📦 where this page comes from