io: fix nasty io_wake corner case.

[ccan] / ccan / io / io.c

diff --git a/ccan/io/io.c b/ccan/io/io.c
index 68b95e82467194f13e87302e907cda5020fe37db..12b2489023d94077d5562db876ab9004caae3dd4 100644 (file)
--- a/ccan/io/io.c
+++ b/ccan/io/io.c
@@ -392,12 +392,25 @@ void io_ready(struct io_conn *conn, int pollflags)
 
 void io_do_always(struct io_conn *conn)
 {
+       /* There's a corner case where the in next_plan wakes up the
+        * out, placing it in IO_ALWAYS and we end up processing it immediately,
+        * only to leave it in the always list.
+        *
+        * Yet we can't just process one, in case they are both supposed
+        * to be done, so grab state beforehand.
+        */
+       bool always_out = (conn->plan[IO_OUT].status == IO_ALWAYS);
+
        if (conn->plan[IO_IN].status == IO_ALWAYS)
                if (!next_plan(conn, &conn->plan[IO_IN]))
                        return;
 
-       if (conn->plan[IO_OUT].status == IO_ALWAYS)
+       if (always_out) {
+               /* You can't *unalways* a conn (except by freeing, in which
+                * case next_plan() returned false */
+               assert(conn->plan[IO_OUT].status == IO_ALWAYS);
                next_plan(conn, &conn->plan[IO_OUT]);
+       }
 }
 
 void io_do_wakeup(struct io_conn *conn, enum io_direction dir)
@@ -483,3 +496,37 @@ struct io_plan *io_set_plan(struct io_conn *conn, enum io_direction dir,
 
        return plan;
 }
+
+bool io_flush_sync(struct io_conn *conn)
+{
+       struct io_plan *plan = &conn->plan[IO_OUT];
+       bool ok;
+
+       /* Not writing?  Nothing to do. */
+       if (plan->status != IO_POLLING)
+               return true;
+
+       /* Synchronous please. */
+       set_blocking(io_conn_fd(conn), true);
+
+again:
+       switch (plan->io(conn->fd.fd, &plan->arg)) {
+       case -1:
+               ok = false;
+               break;
+       /* Incomplete, try again. */
+       case 0:
+               goto again;
+       case 1:
+               ok = true;
+               /* In case they come back. */
+               set_always(conn, IO_OUT, plan->next, plan->next_arg);
+               break;
+       default:
+               /* IO should only return -1, 0 or 1 */
+               abort();
+       }
+
+       set_blocking(io_conn_fd(conn), false);
+       return ok;
+}