Patchwork os-posix: call system_powerdown on SIGTERM, enabling clean guest shutdown

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Submitter Bjørn Mork
Date Nov. 3, 2011, 1:08 p.m.
Message ID <1320325691-9465-1-git-send-email-bjorn@mork.no>
Download mbox | patch
Permalink /patch/123444/
State New
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Comments

Bjørn Mork - Nov. 3, 2011, 1:08 p.m.
Allow well behaved guests to shutdown cleanly when we receive SIGTERM,
e.g. when the host reboots.

The host may be powered down or rebooted while guests are running
without any outer supervision scripts.  These guests will be stopped
by the generic host "sendsigs" script, usually by sending SIGTERM to all
processes still running and then SIGKILL if that didn't work.  Let the
guest power down instead of just killing i instantly.

Signed-off-by: Bjørn Mork <bjorn@mork.no>
---
I wonder if I miss something obvious here... So this patch should be
considered a RFC.  It certainly fixes a small problem for me:  I often
run a number of guests which are started manually, or by simple "runme"
scripts, without any libvirt wrapper or similar.  If/when the host is
rebooted, these guests will be shut down abrubtly with possible guest
file system corruption and other data loss as a consequence. Powering
down on SIGTERM seems like an obious win-win.

I also wonder if it would be useful to do a reboot on HUP, but that
wouldn't solve any real problem so I'm not including it in this 
patch.



Bjørn

 os-posix.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
Anthony Liguori - Nov. 3, 2011, 3:06 p.m.
On 11/03/2011 08:08 AM, Bjørn Mork wrote:
> Allow well behaved guests to shutdown cleanly when we receive SIGTERM,
> e.g. when the host reboots.
>
> The host may be powered down or rebooted while guests are running
> without any outer supervision scripts.  These guests will be stopped
> by the generic host "sendsigs" script, usually by sending SIGTERM to all
> processes still running and then SIGKILL if that didn't work.  Let the
> guest power down instead of just killing i instantly.
>
> Signed-off-by: Bjørn Mork<bjorn@mork.no>

I don't think this is such a good idea.  SIGTERM shouldn't be subject to the 
guest's interpretations.

Instead of doing a killall qemu, just send a system_powerdown command to each 
qemu's monitor instance.

Regards,

Anthony Liguori

> ---
> I wonder if I miss something obvious here... So this patch should be
> considered a RFC.  It certainly fixes a small problem for me:  I often
> run a number of guests which are started manually, or by simple "runme"
> scripts, without any libvirt wrapper or similar.  If/when the host is
> rebooted, these guests will be shut down abrubtly with possible guest
> file system corruption and other data loss as a consequence. Powering
> down on SIGTERM seems like an obious win-win.
>
> I also wonder if it would be useful to do a reboot on HUP, but that
> wouldn't solve any real problem so I'm not including it in this
> patch.
>
>
>
> Bjørn
>
>   os-posix.c |    5 ++++-
>   1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/os-posix.c b/os-posix.c
> index dbf3b24..167fd3b 100644
> --- a/os-posix.c
> +++ b/os-posix.c
> @@ -65,7 +65,10 @@ void os_setup_early_signal_handling(void)
>
>   static void termsig_handler(int signal, siginfo_t *info, void *c)
>   {
> -    qemu_system_killed(info->si_signo, info->si_pid);
> +    if (info->si_signo == SIGTERM)
> +	qemu_system_powerdown_request();
> +    else
> +	qemu_system_killed(info->si_signo, info->si_pid);
>   }
>
>   void os_setup_signal_handling(void)
Bjørn Mork - Nov. 3, 2011, 7:45 p.m.
Anthony Liguori <anthony@codemonkey.ws> writes:

> I don't think this is such a good idea.  SIGTERM shouldn't be subject
> to the guest's interpretations.

OK.  Just an idea.  Thanks for the feedback.

> Instead of doing a killall qemu, just send a system_powerdown command
> to each qemu's monitor instance.

Yes, I know I should.  I am just too lazy to create such scripts for
some of the more occasional guests.  This does of course reflect their
relative importance to me.



Bjørn

Patch

diff --git a/os-posix.c b/os-posix.c
index dbf3b24..167fd3b 100644
--- a/os-posix.c
+++ b/os-posix.c
@@ -65,7 +65,10 @@  void os_setup_early_signal_handling(void)
 
 static void termsig_handler(int signal, siginfo_t *info, void *c)
 {
-    qemu_system_killed(info->si_signo, info->si_pid);
+    if (info->si_signo == SIGTERM)
+	qemu_system_powerdown_request();
+    else
+	qemu_system_killed(info->si_signo, info->si_pid);
 }
 
 void os_setup_signal_handling(void)