From: George Dunlap <george.dunlap@citrix.com>
To: xen-devel@lists.xenproject.org
Cc: Ian Jackson <ian.jackson@citrix.com>,
Olaf Hering <olaf@aepfle.de>, Wei Liu <wei.liu2@citrix.com>
Subject: Re: [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally
Date: Wed, 11 May 2016 12:19:45 +0100 [thread overview]
Message-ID: <57331551.7060105@citrix.com> (raw)
In-Reply-To: <1462965285-5299-2-git-send-email-george.dunlap@citrix.com>
On 11/05/16 12:14, George Dunlap wrote:
> At the moment, the xendomains init script will only create a lockfile
> if when started, it actually does something -- either tries to restore
> a previously saved domain as a result of XENDOMAINS_RESTORE, or tries
> to create a domain as a result of XENDOMAINS_AUTO.
>
> RedHat-based SYSV init systems try to only call "${SERVICE} shutdown"
> on systems which actually have an actively running component; and they
> use the existence of /var/lock/subsys/${SERVICE} to determine which
> systems are running.
>
> This means that at the moment, on RedHat-based SYSV systems (such as
> CentOS 6), if you enable xendomains, and have XENDOMAINS_RESTORE set
> to "true", but don't happen to start a VM, then your running VMs will
> not be suspended on shutdown.
>
> Since the lockfile doesn't really have any other effect than to
> prevent duplicate starting, just create it unconditionally every time
> we start the xendomains script.
>
> The other option would have been to touch the lockfile if
> XENDOMAINS_RESTORE was true regardless of whether there were any
> domains to be restored. But this would mean that if you started with
> the xendomains script active but XENDOMAINS_RESTORE set to "false",
> and then changed it to "true", then xendomains would still not run the
> next time you shut down. This seems to me to violate the principle of
> least surprise.
>
> Signed-off-by: George Dunlap <george.dunlap@citrix.com>
> ---
> CC: Ian Jackson <ian.jackson@citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Olaf Hering <olaf@aepfle.de>
Forgot the release justification.
This is a bug in xendomains under RHEL sysv init systems -- albeit one
that's been there from the beginning. Creating the lockfile
unconditionally shouldn't cause any problems as far as I can tell.
-George
> ---
> tools/hotplug/Linux/xendomains.in | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/tools/hotplug/Linux/xendomains.in b/tools/hotplug/Linux/xendomains.in
> index 727cd42..334d244 100644
> --- a/tools/hotplug/Linux/xendomains.in
> +++ b/tools/hotplug/Linux/xendomains.in
> @@ -255,12 +255,13 @@ start()
> return;
> fi
>
> + mkdir -p $(dirname "$LOCKFILE")
> + touch $LOCKFILE
> +
> saved_domains=" "
> if [ "$XENDOMAINS_RESTORE" = "true" ] &&
> contains_something "$XENDOMAINS_SAVE"
> then
> - mkdir -p $(dirname "$LOCKFILE")
> - touch $LOCKFILE
> echo -n "Restoring Xen domains:"
> saved_domains=`ls $XENDOMAINS_SAVE`
> for dom in $XENDOMAINS_SAVE/*; do
> @@ -286,7 +287,6 @@ start()
>
> if contains_something "$XENDOMAINS_AUTO"
> then
> - touch $LOCKFILE
> echo -n "Starting auto Xen domains:"
> # We expect config scripts for auto starting domains to be in
> # XENDOMAINS_AUTO - they could just be symlinks to files elsewhere
>
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next prev parent reply other threads:[~2016-05-11 11:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-11 11:14 [PATCH for-4.7 1/2] hotplug: Fix xendomains lock path for RHEL-based systems George Dunlap
2016-05-11 11:14 ` [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally George Dunlap
2016-05-11 11:19 ` George Dunlap [this message]
2016-05-11 14:31 ` Wei Liu
2016-05-11 14:30 ` Wei Liu
2016-05-11 14:38 ` Olaf Hering
2016-05-25 12:57 ` George Dunlap
2016-05-11 14:31 ` [PATCH for-4.7 1/2] hotplug: Fix xendomains lock path for RHEL-based systems Wei Liu
2016-05-11 14:37 ` Olaf Hering
2016-05-25 12:55 ` George Dunlap
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