[PATCH 18/29] libxl: cancellation: Provide explicit internal cancel check API

[Ian Jackson <ian.jackson@eu.citrix.com>]

Some places in libxl which can't handle cancellation via a
libxl__ao_cancellable callback might nevertheless benefit from being
able to explicitly check for cancellation.

Provide the (fairly trivial) internal API function to do this.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
v2: New in this version of the series.
---
 tools/libxl/libxl_event.c    |   11 +++++++++++
 tools/libxl/libxl_internal.h |    2 ++
 2 files changed, 13 insertions(+)

diff --git a/tools/libxl/libxl_event.c b/tools/libxl/libxl_event.c
index 55013ef..d3658f1 100644
--- a/tools/libxl/libxl_event.c
+++ b/tools/libxl/libxl_event.c
@@ -2027,6 +2027,17 @@ _hidden int libxl_ao_cancel(libxl_ctx *ctx, const libxl_asyncop_how *how)
     return rc;
 }
 
+int libxl__ao_cancelling(libxl__ao *ao)
+{
+    libxl__ao *root = ao_nested_root(ao);
+    if (root->cancelling) {
+        DBG("ao=%p: cancelling at explicit check (root=%p)", ao, root);
+        return ERROR_CANCELLED;
+    }
+
+    return 0;
+}
+
 int libxl__ao_cancellable_register(libxl__ao_cancellable *canc)
 {
     libxl__ao *ao = canc->ao;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 46383c4..6caf042 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -207,6 +207,8 @@ static inline void libxl__ao_cancellable_init
 static inline bool libxl__ao_cancellable_isregistered
   (const libxl__ao_cancellable *c) { return c->registered; }
 
+int libxl__ao_cancelling(libxl__ao *ao); /* -> 0 or ERROR_CANCELLED */
+
 
 typedef struct libxl__ev_time libxl__ev_time;
 typedef void libxl__ev_time_callback(libxl__egc *egc, libxl__ev_time *ev,
-- 
1.7.10.4