1.\" 2.\" Copyright (c) 1999, 2000 John D. Polstra 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.\" $FreeBSD$ 27.\" 28.Dd July 5, 2000 29.Os 30.Dt DLLOCKINIT 3 31.Sh NAME 32.Nm dllockinit 33.Nd register thread locking methods with the dynamic linker 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.Fd #include <dlfcn.h> 38.Ft void 39.Fn 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)" 40.Sh DESCRIPTION 41.Bf Sy 42Due to enhancements in the dynamic linker, this interface is no longer 43needed. It is deprecated and will be removed from future releases. 44In current releases it still exists, but only as a stub which does nothing. 45.Ef 46.Pp 47Threads packages can call 48.Nm 49at initialization time to register locking functions for the dynamic 50linker to use. This enables the dynamic linker to prevent multiple 51threads from entering its critical sections simultaneously. 52.Pp 53The 54.Fa context 55parameter specifies an opaque context for creating locks. The 56dynamic linker will pass it to the 57.Fa lock_create 58function when creating the locks it needs. When the dynamic linker 59is permanently finished using the locking functions (e.g., if the 60program makes a subsequent call to 61.Nm 62to register new locking functions) it will call 63.Fa context_destroy 64to destroy the context. 65.Pp 66The 67.Fa lock_create 68parameter specifies a function for creating a read/write lock. It 69must return a pointer to the new lock. 70.Pp 71The 72.Fa rlock_acquire 73and 74.Fa wlock_acquire 75parameters specify functions which lock a lock for reading or 76writing, respectively. The 77.Fa lock_release 78parameter specifies a function which unlocks a lock. Each of these 79functions is passed a pointer to the lock. 80.Pp 81The 82.Fa lock_destroy 83parameter specifies a function to destroy a lock. It may be 84.Dv NULL 85if locks do not need to be destroyed. The 86.Fa context_destroy 87parameter specifies a function to destroy the context. It may be 88.Dv NULL 89if the context does not need to be destroyed. 90.Pp 91Until 92.Nm 93is called, the dynamic linker protects its critical sections using 94a default locking mechanism which works by blocking the 95.Dv SIGVTALRM , 96.Dv SIGPROF , 97and 98.Dv SIGALRM 99signals. This is sufficient for many application level threads 100packages, which typically use one of these signals to implement 101preemption. An application which has registered its own locking 102methods with 103.Nm 104can restore the default locking by calling 105.Nm 106with all arguments 107.Dv NULL . 108.Sh SEE ALSO 109.Xr rtld 1 , 110.Xr signal 3 111.Sh HISTORY 112The 113.Nm 114function first appeared in 115.Fx 4.0 . 116