[src/trunk]: src Document that our use of pthread_mutex_unlock(3) is async-si...

[roy <roy%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/82f35e771e36
branches:  trunk
changeset: 330723:82f35e771e36
user:      roy <roy%NetBSD.org@localhost>
date:      Sat Jul 19 14:53:22 2014 +0000

description:
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.

diffstat:

 lib/libc/gen/arc4random.c     |  10 ++++++++--
 lib/libc/gen/pthread_atfork.3 |  13 ++++++++++---
 share/man/man7/signal.7       |   5 +++--
 3 files changed, 21 insertions(+), 7 deletions(-)

diffs (98 lines):

diff -r a3208f44fbaa -r 82f35e771e36 lib/libc/gen/arc4random.c
--- a/lib/libc/gen/arc4random.c Sat Jul 19 14:50:21 2014 +0000
+++ b/lib/libc/gen/arc4random.c Sat Jul 19 14:53:22 2014 +0000
@@ -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 @@
 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;
diff -r a3208f44fbaa -r 82f35e771e36 lib/libc/gen/pthread_atfork.3
--- a/lib/libc/gen/pthread_atfork.3     Sat Jul 19 14:50:21 2014 +0000
+++ b/lib/libc/gen/pthread_atfork.3     Sat Jul 19 14:53:22 2014 +0000
@@ -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 @@
 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 @@
 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 .
diff -r a3208f44fbaa -r 82f35e771e36 share/man/man7/signal.7
--- a/share/man/man7/signal.7   Sat Jul 19 14:50:21 2014 +0000
+++ b/share/man/man7/signal.7   Sat Jul 19 14:53:22 2014 +0000
@@ -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 @@
 .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 ,