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 f298af70781d3fe90e606934614f5d06874e770f..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)