Re: [Qemu-devel] [PATCH] event: Add signal information to SHUTDOWN

["Daniel P. Berrange" <berrange@redhat.com>]

On Thu, Apr 06, 2017 at 04:09:17PM -0500, Eric Blake wrote:
> qemu_kill_report() is already able to tell whether a shutdown
> was triggered by guest action (no output) or by a host signal
> (a message about termination is printed via error_report); but
> this information is then lost.  Libvirt would like to be able
> to distinguish between a SHUTDOWN event triggered solely by
> guest request and one triggered by a SIGTERM on the host.
> 
> Enhance the SHUTDOWN event to pass the value of shutdown_signal
> through to the monitor client, suitably remapped into a
> platform-neutral string.  Note that mingw lacks decent signal
> support, and will never report a signal because it never calls
> qemu_system_killed().

Is it conceivable that we find a non-signal based way to distinguish
guest initiated shutdown, from host OS initiated kill when on Win32 ?

If so, rather than including a 'signal' field in the event, it might
be better to just have a 'source': 'host|guest' field. ie we would
indicate /who/ initiated the shutdown, rather than /how/ it was
initiated.

Or perhaps we should include both the who & the how ?

> See also https://bugzilla.redhat.com/1384007
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  qapi/event.json | 20 +++++++++++++++++++-
>  vl.c            | 21 ++++++++++++++++++---
>  2 files changed, 37 insertions(+), 4 deletions(-)
> 
> diff --git a/qapi/event.json b/qapi/event.json
> index e80f3f4..6aad475 100644
> --- a/qapi/event.json
> +++ b/qapi/event.json
> @@ -5,11 +5,29 @@
>  ##
> 
>  ##
> +# @ShutdownSignal:
> +#
> +# The list of host signal types known to cause qemu to shut down a guest.
> +#
> +# @int: SIGINT
> +# @hup: SIGHUP
> +# @term: SIGTERM
> +#
> +# Since: 2.10
> +##
> +{ 'enum': 'ShutdownSignal', 'data': [ 'int', 'hup', 'term' ] }
> +
> +##
>  # @SHUTDOWN:
>  #
>  # Emitted when the virtual machine has shut down, indicating that qemu is
>  # about to exit.
>  #
> +# @signal: If present, the shutdown was (probably) triggered due to
> +# the receipt of the given signal in the host, rather than by a guest
> +# action (note that there is an inherent race with a guest choosing to
> +# shut down near the same time the host sends a signal). (since 2.10)
> +#
>  # Note: If the command-line option "-no-shutdown" has been specified, qemu will
>  # not exit, and a STOP event will eventually follow the SHUTDOWN event
>  #
> @@ -21,7 +39,7 @@
>  #      "timestamp": { "seconds": 1267040730, "microseconds": 682951 } }
>  #
>  ##
> -{ 'event': 'SHUTDOWN' }
> +{ 'event': 'SHUTDOWN', 'data': { '*signal': 'ShutdownSignal' } }
> 
>  ##
>  # @POWERDOWN:
> diff --git a/vl.c b/vl.c
> index 0b4ed52..af29b2c 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -1626,9 +1626,23 @@ static int qemu_shutdown_requested(void)
>      return atomic_xchg(&shutdown_requested, 0);
>  }
> 
> -static void qemu_kill_report(void)
> +static ShutdownSignal qemu_kill_report(void)
>  {
> +    ShutdownSignal ss = SHUTDOWN_SIGNAL__MAX;
>      if (!qtest_driver() && shutdown_signal != -1) {
> +        switch (shutdown_signal) {
> +        case SIGINT:
> +            ss = SHUTDOWN_SIGNAL_INT;
> +            break;
> +#ifdef SIGHUP
> +        case SIGHUP:
> +            ss = SHUTDOWN_SIGNAL_HUP;
> +            break;
> +#endif
> +        case SIGTERM:
> +            ss = SHUTDOWN_SIGNAL_TERM;
> +            break;
> +        }
>          if (shutdown_pid == 0) {
>              /* This happens for eg ^C at the terminal, so it's worth
>               * avoiding printing an odd message in that case.
> @@ -1644,6 +1658,7 @@ static void qemu_kill_report(void)
>          }
>          shutdown_signal = -1;
>      }
> +    return ss;
>  }
> 
>  static int qemu_reset_requested(void)
> @@ -1852,8 +1867,8 @@ static bool main_loop_should_exit(void)
>          qemu_system_suspend();
>      }
>      if (qemu_shutdown_requested()) {
> -        qemu_kill_report();
> -        qapi_event_send_shutdown(&error_abort);
> +        ShutdownSignal ss = qemu_kill_report();
> +        qapi_event_send_shutdown(ss < SHUTDOWN_SIGNAL__MAX, ss, &error_abort);
>          if (no_shutdown) {
>              vm_stop(RUN_STATE_SHUTDOWN);
>          } else {

If any to the above question means we keep '*signal', then consider this

Reviewed-by: Daniel P. Berrange <berrange@redhat.com>


Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://entangle-photo.org       -o-    http://search.cpan.org/~danberr/ :|