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Document that our use of pthread_mutex_unlock(3) is async-signal-safe 

and as such can be used in a phtread_atfork(3) child handler.
This commit is contained in:
roy 2014-07-19 14:53:22 +00:00
parent a57dc65e45
commit 1ae594017c
3 changed files with 21 additions and 7 deletions
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10
lib/libc/gen/arc4random.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: arc4random.c,v 1.24 2014/06/12 19:12:19 apb Exp $ */
/* $NetBSD: arc4random.c,v 1.25 2014/07/19 14:53:22 roy Exp $ */
/* $OpenBSD: arc4random.c,v 1.6 2001/06/05 05:05:38 pvalchev Exp $ */
/*
@ -27,7 +27,7 @@
#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: arc4random.c,v 1.24 2014/06/12 19:12:19 apb Exp $");
__RCSID("$NetBSD: arc4random.c,v 1.25 2014/07/19 14:53:22 roy Exp $");
#endif /* LIBC_SCCS and not lint */
#include "namespace.h"
@ -125,6 +125,12 @@ arc4_fork_child(void)
static inline void
arc4_check_init(struct arc4_stream *as)
{
/*
* pthread_atfork(3) only allows async-signal-safe functions in
* the child handler.
* NetBSD's mutex_unlock is async-signal safe, other implementations
* may not be.
*/
if (__predict_false(!as->inited)) {
as->inited = true;

13
lib/libc/gen/pthread_atfork.3
View File

@ -1,4 +1,4 @@
.\" $NetBSD: pthread_atfork.3,v 1.5 2008/04/30 13:10:50 martin Exp $
.\" $NetBSD: pthread_atfork.3,v 1.6 2014/07/19 14:53:22 roy Exp $
.\"
.\" Copyright (c) 2003 The NetBSD Foundation, Inc.
.\" All rights reserved.
@ -27,7 +27,7 @@
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd February 12, 2003
.Dd July 18, 2014
.Dt PTHREAD_ATFORK 3
.Os
.Sh NAME
@ -91,7 +91,9 @@ The following error code may be returned:
Insufficient memory exists to register the fork handlers.
.El
.Sh SEE ALSO
.Xr fork 2
.Xr fork 2 ,
.Xr pthread_mutex 3 ,
.Xr signal 7
.Sh STANDARDS
The
.Fn pthread_atfork
@ -115,6 +117,11 @@ functions are not async-signal-safe, so it is not safe to use such functions
in the
.Ar child
handler.
POSIX does not mandate that
.Fn pthread_mutex_unlock
be async-signal-safe, but it is in NetBSD and thus safe to use within the
.Ar child
handler.
.Sh BUGS
There is no way to unregister a handler registered with
.Fn pthread_atfork .

5
share/man/man7/signal.7
View File

@ -1,4 +1,4 @@
.\" $NetBSD: signal.7,v 1.16 2011/01/19 04:33:13 uwe Exp $
.\" $NetBSD: signal.7,v 1.17 2014/07/19 14:53:22 roy Exp $
.\"
.\" Copyright (c) 1999 The NetBSD Foundation, Inc.
.\" All rights reserved.
@ -24,7 +24,7 @@
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd February 27, 2009
.Dd July 18, 2014
.Dt SIGNAL 7
.Os
.Sh NAME
@ -148,6 +148,7 @@ below is unsafe to use in signal handlers.
.Xr poll 2 ,
.\" .Xr posix_trace_event 2
.\" .Xr pselect 2
.Xr pthread_mutex_unlock 3 ,
.Xr raise 3 ,
.Xr read 2 ,
.Xr readlink 2 ,