3 files changed, 124 insertions, 1 deletions
diff --git a/lib/libc/gen/Makefile.inc b/lib/libc/gen/Makefile.inc
index 9a23677..a193cc2 100644
--- a/lib/libc/gen/Makefile.inc
+++ b/lib/libc/gen/Makefile.inc
@@ -34,7 +34,7 @@ SRCS+=  _rand48.c _spinlock_stub.c alarm.c arc4random.c assert.c \
 .if ${LIB} == "c"
 MAN3+=  alarm.3 arc4random.3 clock.3 \
 	confstr.3 crypt.3 ctermid.3 daemon.3 \
-	devname.3 directory.3 dladdr.3 dlopen.3 \
+	devname.3 directory.3 dladdr.3 dllockinit.3 dlopen.3 \
 	err.3 exec.3 fnmatch.3 frexp.3 ftok.3 fts.3 \
 	getbootfile.3 getbsize.3 getcap.3 getcwd.3 \
 	getdiskbyname.3 getdomainname.3 getfsent.3 \
diff --git a/lib/libc/gen/dlfcn.c b/lib/libc/gen/dlfcn.c
index ff77b79..fd0be34 100644
--- a/lib/libc/gen/dlfcn.c
+++ b/lib/libc/gen/dlfcn.c
@@ -78,6 +78,20 @@ dlerror(void)
 	return sorry;
 }
 
+#pragma weak dllockinit
+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))
+{
+	if (context_destroy != NULL)
+		context_destroy(context);
+}
+
 #pragma weak dlopen
 void *
 dlopen(const char *name, int mode)
diff --git a/lib/libc/gen/dllockinit.3 b/lib/libc/gen/dllockinit.3
new file mode 100644
index 0000000..facb18b
--- /dev/null
+++ b/lib/libc/gen/dllockinit.3
@@ -0,0 +1,109 @@
+.\"
+.\" Copyright (c) 1999 John D. Polstra
+.\" All rights reserved.
+.\"
+.\" Redistribution and use in source and binary forms, with or without
+.\" modification, are permitted provided that the following conditions
+.\" are met:
+.\" 1. Redistributions of source code must retain the above copyright
+.\"    notice, this list of conditions and the following disclaimer.
+.\" 2. Redistributions in binary form must reproduce the above copyright
+.\"    notice, this list of conditions and the following disclaimer in the
+.\"    documentation and/or other materials provided with the distribution.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+.\" SUCH DAMAGE.
+.\"
+.\" $FreeBSD$
+.\"
+.Dd December 26, 1999
+.Os FreeBSD
+.Dt DLLOCKINIT 3
+.Sh NAME
+.Nm dllockinit
+.Nd register thread locking methods with the dynamic linker
+.Sh SYNOPSIS
+.Fd #include <dlfcn.h>
+.Ft void
+.Fn dllockinit "const 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)"
+.Sh DESCRIPTION
+Threads packages can call
+.Nm
+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.
+.Pp
+The
+.Fa context
+parameter specifies an opaque context for creating locks.  The
+dynamic linker will pass it to the
+.Fa 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
+.Nm
+to register new locking functions) it will call
+.Fa context_destroy
+to destroy the context.
+.Pp
+The
+.Fa lock_create
+parameter specifies a function for creating a read/write lock.  It
+must return a pointer to the new lock.
+.Pp
+The
+.Fa rlock_acquire
+and
+.Fa wlock_acquire
+parameters specify functions which lock a lock for reading or
+writing, respectively.  The
+.Fa lock_release
+parameter specifies a function which unlocks a lock.  Each of these
+functions is passed a pointer to the lock.
+.Pp
+The
+.Fa lock_destroy
+parameter specifies a function to destroy a lock.  It may be
+.Dv NULL
+if locks do not need to be destroyed.  The
+.Fa context_destroy
+specifies a function to destroy the context.  It may be
+.Dv NULL
+if the context does not need to be destroyed.
+.Pp
+Before
+.Nm
+is called, the dynamic linker protects its critical sections by
+blocking the
+.Dv SIGVTALRM ,
+.Dv SIGPROF ,
+and
+.Dv 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 
+.Nm
+can restore the default locking by calling
+.Nm
+with all arguments
+.Dv NULL .
+.Sh SEE ALSO
+.Xr rtld 1 ,
+.Xr signal 3
+.Sh HISTORY
+The
+.Nm
+function first appeared in FreeBSD 4.0.