Guard the NetBSD block device hotplug script against concurrent execution.

xl(1) runs the hotplug scripts in parallel.  This causes failures when the
next free vnd device is selected.

Locking modeled after the Linux block hotplug script.

6 files changed, 147 insertions, 9 deletions

diff --git a/sysutils/xentools42/Makefile b/sysutils/xentools42/Makefile
index c7b8e19d2aa..24ff4a7a840 100644
--- a/sysutils/xentools42/Makefile
+++ b/sysutils/xentools42/Makefile
@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.43 2016/04/04 15:03:14 bad Exp $
+# $NetBSD: Makefile,v 1.44 2016/04/04 15:13:15 bad Exp $
 
 VERSION=	4.2.5
 VERSION_IPXE=	1.0.0
@@ -145,7 +145,7 @@ SUBST_FILES.conf+=	libxl/xl_cmdtable.c
 SUBST_FILES.conf+=	../docs/misc/xl-disk-configuration.txt
 SUBST_SED.conf=		-e "s,@XENDCONFDIR@,${PKG_SYSCONFDIR},g"
 
-XEND_SCRIPTS=		block vif-bridge vif-ip qemu-ifup hotplugpath.sh
+XEND_SCRIPTS=		block vif-bridge vif-ip qemu-ifup hotplugpath.sh locking.sh
 
 SUBST_CLASSES.NetBSD+=	proc
 SUBST_STAGE.proc=	pre-configure
@@ -200,6 +200,7 @@ pre-build:
 .for s in ${BLKTAP_FILES}
 	${CP} -f ${FILESDIR}/${s} ${WRKSRC}/blktap/drivers/
 .endfor
+	${CP} -f ${FILESDIR}/locking.sh  ${WRKSRC}/hotplug/NetBSD/
 	${SED} -e "s,@XENDCONFDIR@,${PKG_SYSCONFDIR},g" \
 		${XENTOP}/docs/man/xl.pod.1 |\
 	    pod2man >${WRKDIR}/xl.1
diff --git a/sysutils/xentools42/PLIST b/sysutils/xentools42/PLIST
index b9fe9ede9fc..d579cc288cf 100644
--- a/sysutils/xentools42/PLIST
+++ b/sysutils/xentools42/PLIST
@@ -1,4 +1,4 @@
-@comment $NetBSD: PLIST,v 1.6 2014/03/11 14:05:17 jperkin Exp $
+@comment $NetBSD: PLIST,v 1.7 2016/04/04 15:13:15 bad Exp $
 bin/libxl-save-helper
 bin/lsevtchn
 bin/pygrub
@@ -682,6 +682,7 @@ share/examples/xen/formats
 share/examples/xen/oxenstored.conf
 share/examples/xen/scripts/block
 share/examples/xen/scripts/hotplugpath.sh
+share/examples/xen/scripts/locking.sh
 share/examples/xen/scripts/qemu-ifup
 share/examples/xen/scripts/vif-bridge
 share/examples/xen/scripts/vif-ip
diff --git a/sysutils/xentools42/distinfo b/sysutils/xentools42/distinfo
index fe05d4ab364..34624db2977 100644
--- a/sysutils/xentools42/distinfo
+++ b/sysutils/xentools42/distinfo
@@ -1,4 +1,4 @@
-$NetBSD: distinfo,v 1.24 2016/04/04 15:03:14 bad Exp $
+$NetBSD: distinfo,v 1.25 2016/04/04 15:13:15 bad Exp $
 
 SHA1 (ipxe-git-v1.0.0.tar.gz) = da052c8de5f3485fe0253c19cf52ed6d72528485
 RMD160 (ipxe-git-v1.0.0.tar.gz) = dcd9b6eaafa1ce05c1ebf2a15f2f73ad7a8c5547
@@ -48,7 +48,8 @@ SHA1 (patch-firmware_etherboot_patches_boot__prompt__option.patch) = 95d6e140643
 SHA1 (patch-firmware_etherboot_patches_series) = 2ced4e380f436a0287744e0a817ff24b91a43e7c
 SHA1 (patch-firmware_hvmloader_Makefile) = d4d9f34335a178f50e7fda52747cf6551ceeccc6
 SHA1 (patch-firmware_hvmloader_util.h) = 8ec0efdf56b9f2ea66cac7e90cba4abf727d4605
-SHA1 (patch-hotplug_NetBSD_Makefile) = 7b14179d0d00dc1b6f9a85fff706d82ce9b0cd66
+SHA1 (patch-hotplug_NetBSD_Makefile) = efc7c4d5b2f4aa5d3de2c7f77427db77fd95898a
+SHA1 (patch-hotplug_NetBSD_block) = 61a1d5188abd280aa0960fffb6f43fd17bd6fb07
 SHA1 (patch-hotplug_NetBSD_vif-bridge) = 7d01f15273c983c2cfe125e75800f9719961427c
 SHA1 (patch-hotplug_NetBSD_vif-ip) = d3b0555f5ba0bfcbf0f7027eb5f74a84d0cf7c80
 SHA1 (patch-hotplug_common_Makefile) = 3ee2fec5c4cb171c35c7e73379da4235b5ddca99
diff --git a/sysutils/xentools42/files/locking.sh b/sysutils/xentools42/files/locking.sh
new file mode 100644
index 00000000000..88257f62b7b
--- /dev/null
+++ b/sysutils/xentools42/files/locking.sh
@@ -0,0 +1,72 @@
+#!/bin/sh
+#
+# Copyright (c) 2016, Christoph Badura.  All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS
+# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+# DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT,
+# INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+
+LOCK_BASEDIR="$XEN_LOCK_DIR/xen-hotplug"
+
+_lockfd=9
+_have_lock=0	# lock not taken yet.
+
+SHLOCK="shlock ${_shlock_debug-}"
+
+_lock_set_vars() {
+	_lockfile="$LOCK_BASEDIR/$1.lock"
+	_lockfifo="$LOCK_BASEDIR/$1.fifo"
+}
+
+_lock_init() {
+	mkdir -p "$LOCK_BASEDIR" 2>/dev/null || true
+	mkfifo $_lockfifo 2>/dev/null || true
+}
+
+#
+# use a named pipe as condition variable
+# opening for read-only blocks when there's no writer.
+# opening for read-write never blocks but unblocks any waiting readers.
+# 
+_lock_wait_cv() {
+	eval "exec $_lockfd<  $_lockfifo ; exec $_lockfd<&-"
+}
+_lock_signal_cv() {
+	eval "exec $_lockfd<> $_lockfifo ; exec $_lockfd<&-"
+}
+
+claim_lock() {
+	_lock_set_vars $1
+	_lock_init
+	until $SHLOCK -f $_lockfile -p $$; do
+		_lock_wait_cv
+	done
+	_have_lock=1
+	# be sure to release the lock when the shell exits
+	trap "release_lock $1" 0 1 2 15
+}
+
+release_lock() {
+	_lock_set_vars $1
+	[ "$_have_lock" != 0 -a -f $_lockfile ] && rm $_lockfile
+	_have_lock=0
+	_lock_signal_cv;
+}
diff --git a/sysutils/xentools42/patches/patch-hotplug_NetBSD_Makefile b/sysutils/xentools42/patches/patch-hotplug_NetBSD_Makefile
index 023f95d75d1..6701ba3cbd6 100644
--- a/sysutils/xentools42/patches/patch-hotplug_NetBSD_Makefile
+++ b/sysutils/xentools42/patches/patch-hotplug_NetBSD_Makefile
@@ -1,8 +1,14 @@
-$NetBSD: patch-hotplug_NetBSD_Makefile,v 1.2 2015/08/23 16:17:12 spz Exp $
+$NetBSD: patch-hotplug_NetBSD_Makefile,v 1.3 2016/04/04 15:13:15 bad Exp $
 
 --- hotplug/NetBSD/Makefile.orig	2014-09-02 06:22:57.000000000 +0000
 +++ hotplug/NetBSD/Makefile
-@@ -8,7 +8,7 @@ XEN_SCRIPTS += vif-bridge
+@@ -3,12 +3,13 @@ include $(XEN_ROOT)/tools/Rules.mk
+ 
+ # Xen script dir and scripts to go there.
+ XEN_SCRIPTS =
++XEN_SCRIPTS += locking.sh
+ XEN_SCRIPTS += block
+ XEN_SCRIPTS += vif-bridge
  XEN_SCRIPTS += vif-ip
  
  XEN_SCRIPT_DATA =
@@ -11,7 +17,7 @@ $NetBSD: patch-hotplug_NetBSD_Makefile,v 1.2 2015/08/23 16:17:12 spz Exp $
  
  .PHONY: all
  all:
-@@ -21,10 +21,11 @@ install: all install-scripts install-rcd
+@@ -21,10 +22,11 @@ install: all install-scripts install-rcd
  
  .PHONY: install-scripts
  install-scripts:
@@ -25,7 +31,7 @@ $NetBSD: patch-hotplug_NetBSD_Makefile,v 1.2 2015/08/23 16:17:12 spz Exp $
  	done
  	set -e; for i in $(XEN_SCRIPT_DATA); \
  	   do \
-@@ -33,12 +34,6 @@ install-scripts:
+@@ -33,12 +35,6 @@ install-scripts:
  
  .PHONY: install-rcd
  install-rcd:
diff --git a/sysutils/xentools42/patches/patch-hotplug_NetBSD_block b/sysutils/xentools42/patches/patch-hotplug_NetBSD_block
new file mode 100644
index 00000000000..5095cc42656
--- /dev/null
+++ b/sysutils/xentools42/patches/patch-hotplug_NetBSD_block
@@ -0,0 +1,57 @@
+$NetBSD: patch-hotplug_NetBSD_block,v 1.1 2016/04/04 15:13:15 bad Exp $
+
+--- hotplug/NetBSD/block.orig	2014-09-02 06:22:57.000000000 +0000
++++ hotplug/NetBSD/block
+@@ -6,6 +6,7 @@
+ 
+ DIR=$(dirname "$0")
+ . "${DIR}/hotplugpath.sh"
++. "${DIR}/locking.sh"
+ 
+ PATH=${BINDIR}:${SBINDIR}:${LIBEXEC}:${PRIVATE_BINDIR}:/bin:/usr/bin:/sbin:/usr/sbin
+ export PATH
+@@ -14,6 +15,7 @@ error() {
+ 	echo "$@" >&2
+ 	xenstore-write $xpath/hotplug-status error \
+ 	               $xpath/hotplug-error "$@"
++	release_lock block
+ 	exit 1
+ }
+ 	
+@@ -37,10 +39,12 @@ case $xstatus in
+ 	# device removed
+ 	case $xtype in
+ 	file)
++		claim_lock block
+ 		vnd=$(xenstore-read "$xpath/vnd" || echo none)
+ 		if [ $vnd != none ]; then
+ 			vnconfig -u $vnd
+ 		fi
++		release_lock block
+ 		;;
+ 	phy)
+ 		;;
+@@ -52,6 +56,7 @@ case $xstatus in
+ 	exit 0
+ 	;;
+ 2)
++	claim_lock block
+ 	case $xtype in
+ 	file)
+ 		# Store the list of available vnd(4) devices in
+@@ -78,6 +83,7 @@ case $xstatus in
+ 			fi
+ 		done
+ 		if [ x$device = x ] ; then
++			release_lock block
+ 			error "no available vnd device"
+ 		fi
+ 		xenstore-write $xpath/vnd $device
+@@ -89,6 +95,7 @@ case $xstatus in
+ 	physical_device=$(stat -f '%r' "$device")
+ 	xenstore-write $xpath/physical-device $physical_device
+ 	xenstore-write $xpath/hotplug-status connected
++	release_lock block
+ 	exit 0
+ 	;;
+ *)