[Xcb] [PATCH xcb] don't flag extra reply in xcb_take_socket

[Erik Kurzinger]

Hi Uli,

Thanks for taking a look! I tried modifying the 'else' case in _xcb_in_replies_done
as you suggested, I agree that it's a bit cleaner than what I had. 

It still appears to fix the hang in the example program as well as the KWin crash
I had mentioned so everything looks good. I can't think of a better name than 
'prev_next' either - it'll have to do :)

Cheers,
Erik

---
 src/xcb_in.c  | 16 ++++++++++++++--
 src/xcb_out.c | 10 ++++++++--
 2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/src/xcb_in.c b/src/xcb_in.c
index 73209e0..58fe896 100644
--- a/src/xcb_in.c
+++ b/src/xcb_in.c
@@ -958,8 +958,20 @@ void _xcb_in_replies_done(xcb_connection_t *c)
         pend = container_of(c->in.pending_replies_tail, struct pending_reply, next);
         if(pend->workaround == WORKAROUND_EXTERNAL_SOCKET_OWNER)
         {
-            pend->last_request = c->out.request;
-            pend->workaround = WORKAROUND_NONE;
+            if (XCB_SEQUENCE_COMPARE(pend->first_request, <=, c->out.request)) {
+                pend->last_request = c->out.request;
+                pend->workaround = WORKAROUND_NONE;
+            } else {
+                /* The socket was taken, but no requests were actually sent
+                 * so just discard the pending_reply that was created.
+                 */
+                struct pending_reply **prev_next = &c->in.pending_replies;
+                while (*prev_next != pend)
+                    prev_next = &(*prev_next)->next;
+                *prev_next = NULL;
+                c->in.pending_replies_tail = prev_next;
+                free(pend);
+            }
         }
     }
 }
diff --git a/src/xcb_out.c b/src/xcb_out.c
index 3601a5f..c9593e5 100644
--- a/src/xcb_out.c
+++ b/src/xcb_out.c
@@ -387,8 +387,14 @@ int xcb_take_socket(xcb_connection_t *c, void (*return_socket)(void *closure), v
     {
         c->out.return_socket = return_socket;
         c->out.socket_closure = closure;
-        if(flags)
-            _xcb_in_expect_reply(c, c->out.request, WORKAROUND_EXTERNAL_SOCKET_OWNER, flags);
+        if(flags) {
+            /* c->out.request + 1 will be the first request sent by the external
+             * socket owner. If the socket is returned before this request is sent
+             * it will be detected in _xcb_in_replies_done and this pending_reply
+             * will be discarded.
+             */
+            _xcb_in_expect_reply(c, c->out.request + 1, WORKAROUND_EXTERNAL_SOCKET_OWNER, flags);
+        }
         assert(c->out.request == c->out.request_written);
         *sent = c->out.request;
     }
-- 
2.18.0