[PATCH] libxl: Always set ao for qmp_proxy_spawn_outcome

[Jason Andryuk <jandryuk@xxxxxxxxx>]

I've observed this failed assertion:
libxl_event.c:2057: libxl__ao_inprogress_gc: Assertion `ao' failed.

AFAICT, this is happening in qmp_proxy_spawn_outcome where
sdss->qmp_proxy_spawn.ao is NULL.

The out label of spawn_stub_launch_dm calls qmp_proxy_spawn_outcome, but
it is only in the success path that sdss->qmp_proxy_spawn.ao gets set to
the current ao.  Move the setting earlier to have an ao in all paths
through the function.

Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
---
Another option would be to make spawn_stub_launch_dm call
spawn_stubdom_pvqemu_cb on error.  This avoids needing to set
sdss->qmp_proxy_spawn.ao, but it makes more paths through the code.
---
 tools/libs/light/libxl_dm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/libs/light/libxl_dm.c b/tools/libs/light/libxl_dm.c
index 9a8ddbe188..59a8dcf3a9 100644
--- a/tools/libs/light/libxl_dm.c
+++ b/tools/libs/light/libxl_dm.c
@@ -2468,6 +2468,9 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
     uint32_t dm_domid = sdss->pvqemu.guest_domid;
     int need_qemu;
 
+    /* Set for out label through qmp_proxy_spawn_outcome(). */
+    sdss->qmp_proxy_spawn.ao = ao;
+
     if (ret) {
         LOGD(ERROR, guest_domid, "error connecting disk devices");
         goto out;
@@ -2567,7 +2570,6 @@ static void spawn_stub_launch_dm(libxl__egc *egc,
             goto out;
     }
 
-    sdss->qmp_proxy_spawn.ao = ao;
     if (libxl__stubdomain_is_linux(&guest_config->b_info)) {
         spawn_qmp_proxy(egc, sdss);
     } else {
-- 
2.35.1