#

# Posted upstream:

# https://sourceware.org/ml/libc-alpha/2013-10/msg00065.html

#

# This is related to bug 1013801 in that it fixes the problem

# by modifying the runtime. In bug 1013801 we have libselinux

# using pthread_atfork which pulls in libpthread, but we don't

# want that, we want libpthread to be pulled in only when

# actually needed by the application. This patch makes it

# possible to avoid requiring libpthread and still use

# pthread_atfork.

#

# The general idea for the design is in the leading comment

# in the source code.

#

diff --git a/nptl/sysdeps/unix/sysv/linux/Makefile b/nptl/sysdeps/unix/sysv/linux/Makefile

index 6078e2d..36fd50b 100644

--- a/nptl/Makefile

+++ b/nptl/Makefile

@@ -18,7 +18,9 @@

 routines = alloca_cutoff forward libc-lowlevellock libc-cancellation \

 	   libc-cleanup libc_pthread_init libc_multiple_threads \

-	   register-atfork unregister-atfork

+	   register-atfork unregister-atfork libc_pthread_atfork

+

+static-only-routines += libc_pthread_atfork

 shared-only-routines = forward

 libpthread-routines = nptl-init vars events version pt-interp \

diff --git a/nptl/libc_pthread_atfork.c b/nptl/libc_pthread_atfork.c

new file mode 100644

index 0000000..667049a

--- /dev/null

+++ b/nptl/libc_pthread_atfork.c

@@ -0,0 +1,54 @@

+/* Copyright (C) 2013 Free Software Foundation, Inc.

+   This file is part of the GNU C Library.

+   Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.

+

+   The GNU C Library is free software; you can redistribute it and/or

+   modify it under the terms of the GNU Lesser General Public

+   License as published by the Free Software Foundation; either

+   version 2.1 of the License, or (at your option) any later version.

+

+   The GNU C Library is distributed in the hope that it will be useful,

+   but WITHOUT ANY WARRANTY; without even the implied warranty of

+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

+   Lesser General Public License for more details.

+

+   You should have received a copy of the GNU Lesser General Public

+   License along with the GNU C Library; if not, see

+   <http://www.gnu.org/licenses/>.  */

+

+/* The standard design pattern for making it optional to link against

+   libpthread is to mark the function weak, test if the function

+   address is non-zero and call the function, otherwise use a fallback.

+   The problem with pthread_atfork is that there is no viable

+   fallback.  If you need to do something during fork it has to be done

+   via pthread_atfork.  This makes having libpthread optional and using

+   pthread_atfork impossible.  We make it possible by providing

+   pthread_atfork in libc_nonshared.a.  The real work of pthread_atfork

+   is done by __register_atfork which is already provided in

+   libc_nonshared.a.  It's included in libc_nonshared.a because

+   __dso_handle has to be unique to each DSO such that unloading the DSO

+   can unregister the atfork handlers.  We build pthread_atfork again

+   under a different file name and include it into libc_nonshared.a and

+   libc.a. We keep pthread_atfork in libpthread_nonshared.a and

+   libpthread.a for compatibility and completeness.

+

+   Applications that can't rely on a new glibc should use the following

+   code to optionally include libpthread and still register a function

+   via pthread_atfork i.e. use __register_atfork directly:

+

+   extern void *__dso_handle __attribute__ ((__weak__, __visibility__ ("hidden")));

+   extern int __register_atfork (void (*) (void), void (*) (void), void (*) (void), void *);

+

+   static int __app_atfork (void (*prepare) (void), void (*parent) (void), void (*child) (void))

+     {

+       return __register_atfork (prepare, parent, child,

+				 &__dso_handle == NULL ? NULL : __dso_handle);

+     }

+

+   This code requires glibc 2.3.2 or newer. Previous to 2.3.2 no such

+   interfaces exist and at that point is is impossible to have an

+   optional libpthread and call pthread_atfork.

+

+   This code adds no more ABI requirements than already exist since

+   __dso_handle and __register_atfork are already part of the ABI.  */

+#include <pthread_atfork.c>