[src/trunk]: src/share/man/man9 - document XC_HIGHPRI

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

details:   https://anonhg.NetBSD.org/src/rev/681a3a2f8e9c
branches:  trunk
changeset: 770576:681a3a2f8e9c
user:      yamt <yamt%NetBSD.org@localhost>
date:      Mon Oct 24 07:25:51 2011 +0000

description:
- document XC_HIGHPRI
- explicitly note that xc_wait requires thread context.

diffstat:

 share/man/man9/xcall.9 |  19 ++++++++++++++++---
 1 files changed, 16 insertions(+), 3 deletions(-)

diffs (54 lines):

diff -r e7b4584fb28b -r 681a3a2f8e9c share/man/man9/xcall.9
--- a/share/man/man9/xcall.9    Mon Oct 24 02:08:22 2011 +0000
+++ b/share/man/man9/xcall.9    Mon Oct 24 07:25:51 2011 +0000
@@ -1,4 +1,4 @@
-.\"     $NetBSD: xcall.9,v 1.7 2010/12/02 12:54:13 wiz Exp $
+.\"     $NetBSD: xcall.9,v 1.8 2011/10/24 07:25:51 yamt Exp $
 .\"
 .\" Copyright (c) 2010 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 May 16, 2010
+.Dd October 24, 2011
 .Dt XCALL 9
 .Os
 .Sh NAME
@@ -81,6 +81,15 @@
 not interrupting other code running on the CPU, and so has exclusive
 access to the CPU.
 Keep in mind that unless disabled, it may cause a kernel preemption.
+.Pp
+.Nm
+also provides a mechanism for making
+.Dq "high priority"
+cross calls.
+The function to be executed runs on the remote CPU within a
+.Dv IPL_SOFTCLOCK
+software interrupt context, possibly interrupting other lower-priority
+code running on the CPU.
 .Sh NOTES
 Functions being called should be relatively lightweight.
 They may block on locks, but carefully and minimally, to not interfere
@@ -101,7 +110,9 @@
 .Fn xc_wait
 on for the cross-call to complete.
 .Fa flags
-should be 0.
+should be
+.Dv XC_HIGHPRI
+for a "high priority" call, and 0 for a "low priority" call.
 .Fn xc_broadcast
 should not be called from interrupt context.
 .It Fn xc_unicast "flags" "func" "arg1" "arg2" "ci"
@@ -122,6 +133,8 @@
 or
 .Fn xc_unicast
 for the corresponding cross-call to complete.
+.Fn xc_wait
+should be called from a thread context.
 .El
 .Sh CODE REFERENCES
 The