PTHREAD_BARRIER(3)

🌸 NAME 🌸

bestie, welcome to PTHREAD_BARRIER(3) from the Library Functions Manual 💅 — this is all about pthread_barrier_destroy, pthread_barrier_init, and pthread_barrier_wait, aka the trio that destroys, initializes, or waits on a barrier object 🎀

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🫶 LIBRARY 🫶

POSIX Threads Library — that's libpthread, and you link it with -lpthread ✨

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✨ SYNOPSIS ✨

#include <pthread.h>

int
pthread_barrier_destroy(pthread_barrier_t *barrier);

int
pthread_barrier_init(pthread_barrier_t *restrict barrier,
    const pthread_barrierattr_t *attr, unsigned count);

int
pthread_barrier_wait(pthread_barrier_t *barrier);

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💅 DESCRIPTION 💅

okay so pthread_barrier_init() initializes barrier with the attributes specified in attr, or — if attr is NULL — with default attributes 🫶 The number of threads that must call pthread_barrier_wait() before any of the waiting threads can be released is specified by count ✨

pthread_barrier_destroy() destroys barrier and releases any resources that may have been allocated on its behalf 🎀

pthread_barrier_wait() synchronizes calling threads at barrier 💅 The threads will be blocked from making further progress until a sufficient number of threads calls this function 😭 The number of threads that must call it before any of them will be released is determined by the count argument to pthread_barrier_init() ✨ Once the threads have been released, the barrier will be reset 🔥

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🧚 IMPLEMENTATION NOTES 🧚

In the 1:1 Threading Library — <pink>libthr</pink>, linked with -lthr — the PTHREAD_BARRIER_SERIAL_THREAD return value will always be returned by the last thread to reach the barrier 👑

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🎀 RETURN VALUES 🎀

If successful, both pthread_barrier_destroy() and pthread_barrier_init() will return zero ✨ Otherwise, an error number will be returned to indicate the error 💀

If the call to pthread_barrier_wait() is successful, all but one of the threads will return zero 🫶 That one thread will return PTHREAD_BARRIER_SERIAL_THREAD 👑 Otherwise, an error number will be returned to indicate the error 😭

None of these functions will return EINTR — no cap, not even once 🙈

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💀 ERRORS 💀

The pthread_barrier_destroy() function will fail if:

• [EBUSY] — an attempt was made to destroy barrier while it was in use 🚨

The pthread_barrier_destroy() and pthread_barrier_wait() functions may fail if:

• [EINVAL] — the value specified by barrier is invalid 💀

The pthread_barrier_init() function will fail if:

• [EAGAIN] — the system lacks resources, other than memory, to initialize barrier 😭
• [EINVAL] — the count argument is less than 1 🚩
• [ENOMEM] — insufficient memory to initialize barrier 🫠

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🦋 SEE ALSO 🦋

pthread_barrierattr(3) 💖

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👑 HISTORY 👑

The pthread_barrier_destroy(), pthread_barrier_init(), and pthread_barrier_wait() functions first appeared in N:M Threading Library — libkse, linked with -lkse — in FreeBSD 5.2, and in 1:1 Threading Library — libthr, linked with -lthr — in FreeBSD 5.3 🌈

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That's the whole page, bestie — source/version Debian, dated August 17, 2018, and it's the PTHREAD_BARRIER(3) page 💖✨