dllockinit -- register thread locking methods with the dynamic linker
Standard C Library (libc, -lc)
#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));
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.
The context argument specifies 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.
The lock_create argument specifies a function for creating a read/write
lock. It must return a pointer to the new lock.
The rlock_acquire and wlock_acquire arguments specify functions which
lock a lock for reading or writing, respectively. The lock_release argument
specifies a function which unlocks a lock. Each of these functions
is passed a pointer to the lock.
The lock_destroy argument specifies a function to destroy a lock. It may
be NULL if locks do not need to be destroyed. The context_destroy argument
specifies 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.
rtld(1), signal(3)
The dllockinit() function first appeared in FreeBSD 4.0.
FreeBSD 5.2.1 July 5, 2000 FreeBSD 5.2.1 [ Back ] |
