[src/trunk]: src/share/man/man9 add a note on IPL and spinning mutexes

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

details:   https://anonhg.NetBSD.org/src/rev/2b9a71914eec
branches:  trunk
changeset: 757701:2b9a71914eec
user:      ahoka <ahoka%NetBSD.org@localhost>
date:      Tue Sep 14 21:35:53 2010 +0000

description:
add a note on IPL and spinning mutexes

TODO: explain when the IPL will be restored

diffstat:

 share/man/man9/mutex.9 |  9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diffs (30 lines):

diff -r 64e970f36caf -r 2b9a71914eec share/man/man9/mutex.9
--- a/share/man/man9/mutex.9    Tue Sep 14 21:34:02 2010 +0000
+++ b/share/man/man9/mutex.9    Tue Sep 14 21:35:53 2010 +0000
@@ -1,4 +1,4 @@
-.\"    $NetBSD: mutex.9,v 1.22 2010/02/16 19:21:30 rmind Exp $
+.\"    $NetBSD: mutex.9,v 1.23 2010/09/14 21:35:53 ahoka Exp $
 .\"
 .\" Copyright (c) 2007, 2009 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 16, 2010
+.Dd September 14, 2010
 .Dt MUTEX 9
 .Os
 .Sh NAME
@@ -162,6 +162,11 @@
 .Pp
 Adaptive mutexes and other types of lock that can sleep may
 not be acquired while a spin mutex is held by the caller.
+.Pp
+When acquiring a spin mutex, the IPL of the current CPU will be raised to
+the level set in
+.Fn mutex_init
+if it is not already equal or higher.
 .It Fn mutex_exit "mtx"
 .Pp
 Release a mutex.