This exit_wait seems necessary to make the rx side test pass for me.
I think this is just missed from the original test add patch. Add it now.

Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>

---
 tools/testing/selftests/drivers/net/hw/devmem.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/drivers/net/hw/devmem.py b/tools/testing/selftests/drivers/net/hw/devmem.py
index 9b3e2c78f457..6effb9e33fd8 100755
--- a/tools/testing/selftests/drivers/net/hw/devmem.py
+++ b/tools/testing/selftests/drivers/net/hw/devmem.py
@@ -26,7 +26,7 @@ def check_rx(cfg) -> None:
     port = rand_port()
     listen_cmd = f"{cfg.bin_local} -l -f {cfg.ifname} -s {cfg.addr} -p {port}"
 
-    with bkg(listen_cmd) as ncdevmem:
+    with bkg(listen_cmd, exit_wait=True) as ncdevmem:
         wait_port_listen(port)
         cmd(f"echo -e \"hello\\nworld\"| socat -u - TCP{cfg.addr_ipver}:{cfg.addr}:{port}", host=cfg.remote, shell=True)
 
-- 
2.49.0.1151.ga128411c76-goog