Enter mtx_enter_try. In part for completeness, things may start

using this soon(ish).  Ok oga@, sorta yes kettenis@.

2 files changed, 14 insertions, 4 deletions

diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
index bb68a7b5e74..b25798c1a64 100644
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -1,4 +1,4 @@
-#	$OpenBSD: Makefile,v 1.151 2009/04/21 19:30:14 mk Exp $
+#	$OpenBSD: Makefile,v 1.152 2009/04/25 20:14:42 weingart Exp $
 #	$NetBSD: Makefile,v 1.4 1996/01/09 03:23:01 thorpej Exp $
 
 #	Makefile for section 9 (kernel function and variable) manual pages.
@@ -219,7 +219,8 @@ MLINKS+=microtime.9 getmicrotime.9 microtime.9 microuptime.9 \
 	microtime.9 getnanouptime.9 microtime.9 bintime.9 \
 	microtime.9 binuptime.9
 MLINKS+=mountroothook_establish.9 mountroothook_disestablish.9
-MLINKS+=mutex.9 mtx_init.9 mutex.9 mtx_enter.9 mutex.9 mtx_leave.9
+MLINKS+=mutex.9 mtx_init.9 mutex.9 mtx_enter.9 mutex.9 mtx_enter_try.9 \
+	mutex.9 mtx_leave.9
 MLINKS+=namei.9 lookup.9 namei.9 relookup.9 namei.9 NDINIT.9
 MLINKS+=pci_conf_read.9 pci_conf_write.9 pci_conf_read.9 pci_make_tag.9 \
 	pci_conf_read.9 pci_decompose_tag.9
diff --git a/share/man/man9/mutex.9 b/share/man/man9/mutex.9
index 6574d75541f..f10b2992700 100644
--- a/share/man/man9/mutex.9
+++ b/share/man/man9/mutex.9
@@ -1,4 +1,4 @@
-.\" $OpenBSD: mutex.9,v 1.7 2007/12/09 20:54:01 jmc Exp $
+.\" $OpenBSD: mutex.9,v 1.8 2009/04/25 20:14:42 weingart Exp $
 .\"
 .\" Copyright (c) 2005 Pedro Martelletto <pedro@ambientworks.net>
 .\" All rights reserved.
@@ -15,13 +15,14 @@
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 .\"
-.Dd $Mdocdate: December 9 2007 $
+.Dd $Mdocdate: April 25 2009 $
 .Dt MUTEX 9
 .Os
 .Sh NAME
 .Nm mutex ,
 .Nm mtx_init ,
 .Nm mtx_enter ,
+.Nm mtx_enter_try ,
 .Nm mtx_leave
 .Nd interface to CPU mutexes
 .Sh SYNOPSIS
@@ -30,6 +31,8 @@
 .Fn mtx_init "struct mutex *mtxp" "int wantipl"
 .Ft void
 .Fn mtx_enter "struct mutex *mtxp"
+.Ft int
+.Fn mtx_enter_try "struct mutex *mtxp"
 .Ft void
 .Fn mtx_leave "struct mutex *mtxp"
 .Sh DESCRIPTION
@@ -52,6 +55,12 @@ The
 function acquires a mutex, spinning if necessary.
 .Pp
 The
+.Fn mtx_enter_try
+function tries to acquire a mutex.
+On success it will return a non-zero value, zero on failure.
+It is recommended that this function only be used if absolutely necessary.
+.Pp
+The
 .Fn mtx_leave
 function releases a mutex.
 In case the acquisition of the mutex caused the interrupt level to be changed,