[Tools] testbot: Add functions wrapping the VM::ChildPid field.

[Francois Gouget]

They allow checking if the VM status is compatible with having a child
process, checking if the VM has a running process and killing the VM's
child process if any.
This makes the relevant code more readable and more maintainable by
factorizing these operations.

Signed-off-by: Francois Gouget <fgouget at codeweavers.com>
---
 testbot/bin/Engine.pl          | 18 +++++++--------
 testbot/lib/WineTestBot/VMs.pm | 51 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 10 deletions(-)

diff --git a/testbot/bin/Engine.pl b/testbot/bin/Engine.pl
index ee496e2a..b9c6ceb9 100755
--- a/testbot/bin/Engine.pl
+++ b/testbot/bin/Engine.pl
@@ -71,8 +71,8 @@ sub FatalError(@)
 
 =item C<Cleanup()>
 
-The Cleanup() function gets the tasks and VMs in a consistent state on the
-Engine startup or cleanly stops the tasks and VMs on shutdown.
+The Cleanup() function gets the Tasks and VMs in a consistent state on the
+Engine startup or cleanly stops the Tasks and VMs on shutdown.
 It has to contend with three main scenarios:
 - The Engine being restarted. Any task started just before that is still
   running should still have its process and powered on VM and should be left
@@ -81,15 +81,14 @@ It has to contend with three main scenarios:
 - The Engine startup after a reboot. All task processes will be dead and need
   to be requeued. But the VMs are likely to be hosted on a separate machine so
   it is quite possible that they will still be running. Hopefully any running
-  process matching a task's ChildPid will belong to another user so we don't
+  process matching a Task's ChildPid will belong to another user so we don't
   mistake that case for the previous one.
-- A shutdown of the Engine and its tasks / VMs. In this case it's used to
+- A shutdown of the Engine and its Tasks / VMs. In this case it's used to
   kill the running tasks and requeue them, and/or power off the VMs.
 
 In all cases we only trust that a VM status field is still valid if:
-- It is 'running' and used by a task that is still running.
-- It is 'reverting' or 'sleeping', is powered on and the revert process is
-  still running.
+- It is 'running' and used by a Task that is still running.
+- It can have a running process and that process is still running.
 - It is 'idle' and powered on.
 In all other cases the VM will be powered off and marked as such.
 
@@ -187,15 +186,14 @@ sub Cleanup(;$$)
     {
       if ($KillVMs)
       {
-        kill("TERM", $VM->ChildPid) if (defined $VM->ChildPid);
+        $VM->KillChild();
       }
       elsif ($VM->Status eq "idle")
       {
         # Assume these are still ready for use
         next;
       }
-      elsif (($VM->Status eq "reverting" or $VM->Status eq "sleeping") and
-             defined $VM->ChildPid and !kill(0, $VM->ChildPid))
+      elsif ($VM->CanHaveChild() and $VM->HasRunningChild())
       {
         # This VM is still being reverted. Let that process run its course.
         LogMsg "$VMKey is being reverted\n";
diff --git a/testbot/lib/WineTestBot/VMs.pm b/testbot/lib/WineTestBot/VMs.pm
index af052d93..629d4089 100644
--- a/testbot/lib/WineTestBot/VMs.pm
+++ b/testbot/lib/WineTestBot/VMs.pm
@@ -226,6 +226,57 @@ sub Status($;$)
   return $NewStatus;
 }
 
+=pod
+=over 12
+
+=item C<CanHaveChild()>
+
+Returns true if the VM status is compatible with ChildPid being set.
+
+=back
+=cut
+
+sub CanHaveChild($)
+{
+  my ($self) = @_;
+  return ($self->Status =~ /^(?:reverting|sleeping)$/);
+}
+
+=pod
+=over 12
+
+=item C<HasRunningChild()>
+
+Returns true if ChildPid is set and still identifies a running process.
+
+=back
+=cut
+
+sub HasRunningChild($)
+{
+  my ($self) = @_;
+  return undef if (!$self->ChildPid);
+  return kill(0, $self->ChildPid);
+}
+
+=pod
+=over 12
+
+=item C<KillChild()>
+
+If ChildPid is set, kills the corresponding process and unsets ChildPid.
+It is up to the caller to save the updated VM object.
+
+=back
+=cut
+
+sub KillChild($)
+{
+  my ($self) = @_;
+  kill("TERM", $self->ChildPid) if ($self->ChildPid);
+  $self->ChildPid(undef);
+}
+
 sub Validate($)
 {
   my ($self) = @_;
-- 
2.14.2