libxl: event handling: Add an assert to egc_run_callbacks

Check that the ao is still live when we are about to running some of
its callbacks.

This reveals an existing bug in libxl which is exercised by libvirt,
converting
   libvirtd: libxl_event.c:1792: libxl__ao_complete_check_progress_reports: Assertion `ao->in_initiator' failed.
into
   libvirtd: libxl_event.c:1338: egc_run_callbacks: Assertion `aop->ao->magic == 0xA0FACE00ul' failed.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Ian Campbell <ian.campbell@citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Jim Fehlig <jfehlig@suse.com>
Acked-by: Wei Liu <wei.liu2@citrix.com>

diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c
index 0d874d9c585e4de89867508c4dda47c7b3d37a38..ae73728e210e4ef0616110fbceaac5ebe5244944 100644 (file)
--- a/tools/libxl/libxl_event.c
+++ b/tools/libxl/libxl_event.c
@@ -1335,6 +1335,7 @@ static void egc_run_callbacks(libxl__egc *egc)
         aop->how->callback(CTX, aop->ev, aop->how->for_callback);
 
         CTX_LOCK;
+        assert(aop->ao->magic == LIBXL__AO_MAGIC);
         aop->ao->progress_reports_outstanding--;
         libxl__ao_complete_check_progress_reports(egc, aop->ao);
         CTX_UNLOCK;