DLLOCKINIT(3)

🌸 NAME 🌸

dllockinit — register thread locking methods with the dynamic linker. Also hi bestie, this is the DLLOCKINIT(3) page from the Library Functions Manual, folded in right here near the top 🫶

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🎀 LIBRARY 🎀

Standard C Library (libc, -lc) 📚

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✨ SYNOPSIS ✨

#include <dlfcn.h>

void
dllockinit(void *context, void *(*lock_create)(void *context),
    void (*rlock_acquire)(void *lock),
    void (*wlock_acquire)(void *lock), void (*lock_release)(void *lock),
    void (*lock_destroy)(void *lock),
    void (*context_destroy)(void *context));

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💅 DESCRIPTION 💅

Okay so first things first, bestie: this interface is deprecated, and it's deprecated for a reason. Due to enhancements in the dynamic linker, this interface is no longer needed. It is deprecated and will be removed from future releases. In current releases it still exists, but only as a stub which does nothing. 💀

Threads packages can call dllockinit() at initialization time to register locking functions for the dynamic linker to use. This enables the dynamic linker to prevent multiple threads from entering its critical sections simultaneously. 👑

Here's the cast of arguments, because we're not skipping anyone:

• context — an opaque context for creating locks. The dynamic linker will pass it to the lock_create function when creating the locks it needs. When the dynamic linker is permanently finished using the locking functions (e.g., if the program makes a subsequent call to dllockinit() to register new locking functions), it will call context_destroy to destroy the context. ✨
• lock_create — a function for creating a read/write lock. It must return a pointer to the new lock.
• rlock_acquire — a function which locks a lock for reading. It is passed a pointer to the lock.
• wlock_acquire — a function which locks a lock for writing. It is passed a pointer to the lock.
• lock_release — a function which unlocks a lock. It is passed a pointer to the lock.
• lock_destroy — a function to destroy a lock. It may be NULL if locks do not need to be destroyed.
• context_destroy — a function to destroy the context. It may be NULL if the context does not need to be destroyed.

Until dllockinit() is called, the dynamic linker protects its critical sections using a default locking mechanism which works by blocking the SIGVTALRM, SIGPROF, and SIGALRM signals. This is sufficient for many application level threads packages, which typically use one of these signals to implement preemption. An application which has registered its own locking methods with dllockinit() can restore the default locking by calling dllockinit() with all arguments NULL. 🌈

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👀 SEE ALSO 👀

rtld(1), signal(3) 🦋

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🦋 HISTORY 🦋

The dllockinit() function first appeared in FreeBSD 4.0. ⭐

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mwah 💋 — this page's source/version is Debian, dated July 5, 2000. Stay slay, bestie 🎀