PTHREAD_RWLOCK_TIMEDRDLOCK(3)

💖 NAME

okay so this is the pthread_rwlock_timedrdlock(3) page from the Library Functions Manual, and it’s literally all about acquiring a read-write lock for reading — or giving up after a specified period. bestie, the timeout is the whole vibe here. ✨

📚 LIBRARY

POSIX Threads Library (libpthread, -lpthread). slay. 💅

🌸 SYNOPSIS

#include <pthread.h>

int
pthread_rwlock_timedrdlock(pthread_rwlock_t *restrict rwlock,
    const struct timespec *restrict abs_timeout);

🦋 DESCRIPTION

So this function acquires a read lock on the read-write lock rwlock. iconic behavior. but here’s the timed part: if the lock cannot be acquired without waiting for another thread to unlock the lock, this wait shall be terminated when abs_timeout expires. ⏰

A thread may hold multiple concurrent read locks. and listen — pthread_rwlock_unlock(3) must be called once for each lock acquired. no skipping, bestie. 🫶

If the thread should be interrupted by a signal, the pthread_rwlock_timedrdlock() function will be automatically restarted after the thread returns from the signal handler. yes, it comes back. 💖

⚠️ okay important: the calling thread may deadlock if at the time the call is made it holds a write lock on rwlock. also, the results are undefined if this function is called with an uninitialized read-write lock. so please initialize your locks, i am begging. 😭

👑 IMPLEMENTATION NOTES

To prevent writer starvation, writers are favored over readers. periodt. writers get the priority here. 🔥

🎀 RETURN VALUES

If successful, the pthread_rwlock_timedrdlock() function will return zero. otherwise, an error number will be returned to indicate the error. 💫

This function shall not return an error code of EINTR. not me being clear about it. 💅

💅 ERRORS

The pthread_rwlock_timedrdlock() function will fail if:

• [ETIMEDOUT] — The lock could not be acquired before the specified timeout expired. too slow, time’s up. ⏳

The pthread_rwlock_timedrdlock() function may fail if:

• [EAGAIN] — The read lock could not be acquired because the maximum number of read locks for rwlock would be exceeded. bestie, that’s the cap. 🙈
• [EDEADLK] — The calling thread already holds a write lock on rwlock. uh oh. 💀
• [EINVAL] — The value specified by rwlock does not refer to an initialized read-write lock object, or the abs_timeout nanosecond value is less than zero or greater than or equal to 1 billion. check ur values, babes. ⭐

🔥 SEE ALSO

pthread_rwlock_init(3), pthread_rwlock_timedwrlock(3), pthread_rwlock_unlock(3)

🌈 STANDARDS

The pthread_rwlock_timedrdlock() function is expected to conform to ISO/IEC 9945-1:1996 (“POSIX.1”). 💜

⭐ HISTORY

The pthread_rwlock_timedrdlock() function first appeared in FreeBSD 5.2. a whole era. 🦋

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okay that’s the whole page bestie 💖 this one’s from Debian, dated August 17, 2018, and the manual is PTHREAD_RWLOCK_TIMEDRDLOCK(3) — mwah 💅