2ccc347bbb
on a single physical machine. The xentools46 package contains the tools to create, destroy and control the virtual machines. This package contains the tools for Xen 4.6.x
72 lines
2.2 KiB
Bash
72 lines
2.2 KiB
Bash
#!/bin/sh
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#
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# Copyright (c) 2016, Christoph Badura. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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# DISCLAIMED. IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY DIRECT,
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# INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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# SUCH DAMAGE.
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#
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LOCK_BASEDIR="$XEN_LOCK_DIR/xen-hotplug"
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_lockfd=9
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_have_lock=0 # lock not taken yet.
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SHLOCK="shlock ${_shlock_debug-}"
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_lock_set_vars() {
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_lockfile="$LOCK_BASEDIR/$1.lock"
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_lockfifo="$LOCK_BASEDIR/$1.fifo"
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}
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_lock_init() {
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mkdir -p "$LOCK_BASEDIR" 2>/dev/null || true
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mkfifo $_lockfifo 2>/dev/null || true
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}
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#
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# use a named pipe as condition variable
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# opening for read-only blocks when there's no writer.
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# opening for read-write never blocks but unblocks any waiting readers.
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#
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_lock_wait_cv() {
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eval "exec $_lockfd< $_lockfifo ; exec $_lockfd<&-"
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}
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_lock_signal_cv() {
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eval "exec $_lockfd<> $_lockfifo ; exec $_lockfd<&-"
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}
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claim_lock() {
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_lock_set_vars $1
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_lock_init
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until $SHLOCK -f $_lockfile -p $$; do
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_lock_wait_cv
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done
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_have_lock=1
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# be sure to release the lock when the shell exits
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trap "release_lock $1" 0 1 2 15
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}
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release_lock() {
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_lock_set_vars $1
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[ "$_have_lock" != 0 -a -f $_lockfile ] && rm $_lockfile
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_have_lock=0
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_lock_signal_cv;
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}
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