PTHREAD_RWLOCK_WRLOCK(3)

💅 PTHREAD_RWLOCK_WRLOCK(3)

okay so this page lives in the Library Functions Manual, and it's all about grabbing a read/write lock for writing. bestie, if you need to be the main character who gets to write while everyone else reads, this is your moment. 💖

✨ NAME ✨

pthread_rwlock_wrlock, pthread_rwlock_trywrlock — acquire a read/write lock for writing. literally the whole point. 🎀

🫶 LIBRARY 🫶

POSIX Threads Library (libpthread, -lpthread). yes, link it. 💅

🎀 SYNOPSIS 🎀

#include <pthread.h>

int
pthread_rwlock_wrlock(pthread_rwlock_t *lock);

int
pthread_rwlock_trywrlock(pthread_rwlock_t *lock);

💖 DESCRIPTION 💖

pthread_rwlock_wrlock() blocks until a write lock can be acquired against lock. it is not rushing; it waits for its turn. 🧚

pthread_rwlock_trywrlock() performs the same action, but it does not block if the lock cannot be immediately obtained. so it's the “try it and see” version, not the “stand here forever” version. 😭

🚨 real talk though: the results are undefined if the calling thread already holds the lock at the time the call is made. undefined is not a vibe. do not do that. 💀

👑 IMPLEMENTATION NOTES 👑

to prevent writer starvation, writers are favored over readers. periodt. writers get priority so they don't just sit there forever while readers keep cutting the line. 🫶

🔥 RETURN VALUES 🔥

if successful, pthread_rwlock_wrlock() and pthread_rwlock_trywrlock() will return zero. zero is the slay result. ✨

otherwise an error number will be returned to indicate the error. so check your return value, bestie — that's the vibe check. 🔍

🚨 ERRORS 🚨

the pthread_rwlock_trywrlock() function will fail if:

• [EBUSY] — the calling thread is not able to acquire the lock without blocking. it's giving “not right now, try again later.” 🙈

the pthread_rwlock_wrlock() and pthread_rwlock_trywrlock() functions may fail if:

• [EDEADLK] — the calling thread already owns the read/write lock (for reading or writing). bestie, you already have it. no cap. 😭
• [EINVAL] — the value specified by lock is invalid. invalid lock = not iconic. 🚫
• [ENOMEM] — insufficient memory exists to initialize the lock (applies to statically initialized locks only). memory said “no <3”. 💀

🌈 SEE ALSO 🌈

• pthread_rwlock_init(3)
• pthread_rwlock_rdlock(3)
• pthread_rwlock_tryrdlock(3)
• pthread_rwlock_unlock(3)

go read these too, iykyk. 📚💖

⭐ STANDARDS ⭐

the pthread_rwlock_wrlock() and pthread_rwlock_trywrlock() functions are expected to conform to Version 2 of the Single UNIX Specification (“SUSv2”). fancy. 💅

🦋 HISTORY 🦋

the pthread_rwlock_wrlock() function first appeared in FreeBSD 3.0. a classic. 👑

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xoxo bestie 💖 — Debian, August 4, 1998 🎀 — PTHREAD_RWLOCK_WRLOCK(3) out 💅