* Re: [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally
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
2016-05-11 14:31 ` Wei Liu
2016-05-11 14:30 ` Wei Liu
` (2 subsequent siblings)
3 siblings, 1 reply; 10+ messages in thread
From: George Dunlap @ 2016-05-11 11:19 UTC (permalink / raw)
To: xen-devel; +Cc: Ian Jackson, Olaf Hering, Wei Liu
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 $LOCKFILE
> echo -n "Starting auto Xen domains:"
> # We expect config scripts for auto starting domains to be in
> # XENDOMAINS_AUTO - they could just be symlinks to files elsewhere
>
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally
2016-05-11 11:19 ` George Dunlap
@ 2016-05-11 14:31 ` Wei Liu
0 siblings, 0 replies; 10+ messages in thread
From: Wei Liu @ 2016-05-11 14:31 UTC (permalink / raw)
To: George Dunlap; +Cc: xen-devel, Olaf Hering, Wei Liu, Ian Jackson
On Wed, May 11, 2016 at 12:19:45PM +0100, George Dunlap wrote:
> On 11/05/16 12:14, George Dunlap wrote:
> > At the moment, the xendomains init script will only create a lockfile
> > if when started, it actually does something -- either tries to restore
> > a previously saved domain as a result of XENDOMAINS_RESTORE, or tries
> > to create a domain as a result of XENDOMAINS_AUTO.
> >
> > RedHat-based SYSV init systems try to only call "${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.
>
I agree.
Release-acked-by: Wei Liu <wei.liu2@citrix.com>
I've queued this series.
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally
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
@ 2016-05-11 14:30 ` Wei Liu
2016-05-11 14:38 ` Olaf Hering
2016-05-25 12:57 ` George Dunlap
3 siblings, 0 replies; 10+ messages in thread
From: Wei Liu @ 2016-05-11 14:30 UTC (permalink / raw)
To: George Dunlap; +Cc: xen-devel, Olaf Hering, Wei Liu, Ian Jackson
On Wed, May 11, 2016 at 12:14:45PM +0100, 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>
Acked-by: Wei Liu <wei.liu2@citrix.com>
> ---
> CC: Ian Jackson <ian.jackson@citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Olaf Hering <olaf@aepfle.de>
> ---
> 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 $LOCKFILE
> echo -n "Starting auto Xen domains:"
> # We expect config scripts for auto starting domains to be in
> # XENDOMAINS_AUTO - they could just be symlinks to files elsewhere
> --
> 2.1.4
>
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally
2016-05-11 11:14 ` [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally George Dunlap
2016-05-11 11:19 ` George Dunlap
2016-05-11 14:30 ` Wei Liu
@ 2016-05-11 14:38 ` Olaf Hering
2016-05-25 12:57 ` George Dunlap
3 siblings, 0 replies; 10+ messages in thread
From: Olaf Hering @ 2016-05-11 14:38 UTC (permalink / raw)
To: George Dunlap; +Cc: xen-devel, Wei Liu, Ian Jackson
On Wed, May 11, George Dunlap wrote:
> At the moment, the xendomains init script will only create a lockfile
> if when started, it actually does something -- either tries to restore
> a previously saved domain as a result of XENDOMAINS_RESTORE, or tries
> to create a domain as a result of XENDOMAINS_AUTO.
>
> RedHat-based SYSV init systems try to only call "${SERVICE} shutdown"
> on systems which actually have an actively running component; and they
> use the existence of /var/lock/subsys/${SERVICE} to determine which
> systems are running.
>
> This means that at the moment, on RedHat-based SYSV systems (such as
> CentOS 6), if you enable xendomains, and have XENDOMAINS_RESTORE set
> to "true", but don't happen to start a VM, then your running VMs will
> not be suspended on shutdown.
>
> Since the lockfile doesn't really have any other effect than to
> prevent duplicate starting, just create it unconditionally every time
> we start the xendomains script.
Acked-by: Olaf Hering <olaf@aepfle.de>
Olaf
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^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally
2016-05-11 11:14 ` [PATCH for-4.7 2/2] tools/xendomains: Create lockfile on start unconditionally George Dunlap
` (2 preceding siblings ...)
2016-05-11 14:38 ` Olaf Hering
@ 2016-05-25 12:57 ` George Dunlap
3 siblings, 0 replies; 10+ messages in thread
From: George Dunlap @ 2016-05-25 12:57 UTC (permalink / raw)
To: xen-devel; +Cc: Ian Jackson, Olaf Hering, Wei Liu, George Dunlap
On Wed, May 11, 2016 at 12:14 PM, George Dunlap
<george.dunlap@citrix.com> wrote:
> At the moment, the xendomains init script will only create a lockfile
> if when started, it actually does something -- either tries to restore
> a previously saved domain as a result of XENDOMAINS_RESTORE, or tries
> to create a domain as a result of XENDOMAINS_AUTO.
>
> RedHat-based SYSV init systems try to only call "${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>
And this should probably be backported as far back as we're still
doing bugfixes (which I guess would be 4.6 and 4.5?)
-George
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