xen/interface: re-define FRONT/BACK_RING_ATTACH()

Currently these macros are defined to re-initialize a front/back ring
(respectively) to values read from the shared ring in such a way that any
requests/responses that are added to the shared ring whilst the front/back
is detached will be skipped over. This, in general, is not a desirable
semantic since most frontend implementations will eventually block waiting
for a response which would either never appear or never be processed.

Since the macros are currently unused, take this opportunity to re-define
them to re-initialize a front/back ring using specified values. This also
allows FRONT/BACK_RING_INIT() to be re-defined in terms of
FRONT/BACK_RING_ATTACH() using a specified value of 0.

NOTE: BACK_RING_ATTACH() will be used directly in a subsequent patch.

Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/include/xen/interface/io/ring.h b/include/xen/interface/io/ring.h
index 3f40501..2af7a1c 100644 (file)
--- a/include/xen/interface/io/ring.h
+++ b/include/xen/interface/io/ring.h
@@ -125,35 +125,24 @@ struct __name##_back_ring {                                               \
     memset((_s)->pad, 0, sizeof((_s)->pad));                           \
 } while(0)
 
-#define FRONT_RING_INIT(_r, _s, __size) do {                           \
-    (_r)->req_prod_pvt = 0;                                            \
-    (_r)->rsp_cons = 0;                                                        \
+#define FRONT_RING_ATTACH(_r, _s, _i, __size) do {                     \
+    (_r)->req_prod_pvt = (_i);                                         \
+    (_r)->rsp_cons = (_i);                                             \
     (_r)->nr_ents = __RING_SIZE(_s, __size);                           \
     (_r)->sring = (_s);                                                        \
 } while (0)
 
-#define BACK_RING_INIT(_r, _s, __size) do {                            \
-    (_r)->rsp_prod_pvt = 0;                                            \
-    (_r)->req_cons = 0;                                                        \
-    (_r)->nr_ents = __RING_SIZE(_s, __size);                           \
-    (_r)->sring = (_s);                                                        \
-} while (0)
+#define FRONT_RING_INIT(_r, _s, __size) FRONT_RING_ATTACH(_r, _s, 0, __size)
 
-/* Initialize to existing shared indexes -- for recovery */
-#define FRONT_RING_ATTACH(_r, _s, __size) do {                         \
-    (_r)->sring = (_s);                                                        \
-    (_r)->req_prod_pvt = (_s)->req_prod;                               \
-    (_r)->rsp_cons = (_s)->rsp_prod;                                   \
+#define BACK_RING_ATTACH(_r, _s, _i, __size) do {                      \
+    (_r)->rsp_prod_pvt = (_i);                                         \
+    (_r)->req_cons = (_i);                                             \
     (_r)->nr_ents = __RING_SIZE(_s, __size);                           \
-} while (0)
-
-#define BACK_RING_ATTACH(_r, _s, __size) do {                          \
     (_r)->sring = (_s);                                                        \
-    (_r)->rsp_prod_pvt = (_s)->rsp_prod;                               \
-    (_r)->req_cons = (_s)->req_prod;                                   \
-    (_r)->nr_ents = __RING_SIZE(_s, __size);                           \
 } while (0)
 
+#define BACK_RING_INIT(_r, _s, __size) BACK_RING_ATTACH(_r, _s, 0, __size)
+
 /* How big is this ring? */
 #define RING_SIZE(_r)                                                  \
     ((_r)->nr_ents)