From dd75e3d87256f42cdcc65c2d51a6a106dc721729 Mon Sep 17 00:00:00 2001 From: Sergey Organov Date: Wed, 29 Jan 2020 14:21:46 +0300 Subject: [PATCH] usb: gadget: serial: fix Tx stall after buffer overflow MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit [ Upstream commit e4bfded56cf39b8d02733c1e6ef546b97961e18a ] Symptom: application opens /dev/ttyGS0 and starts sending (writing) to it while either USB cable is not connected, or nobody listens on the other side of the cable. If driver circular buffer overflows before connection is established, no data will be written to the USB layer until/unless /dev/ttyGS0 is closed and re-opened again by the application (the latter besides having no means of being notified about the event of establishing of the connection.) Fix: on open and/or connect, kick Tx to flush circular buffer data to USB layer. Signed-off-by: Sergey Organov Reviewed-by: Michał Mirosław Signed-off-by: Felipe Balbi Signed-off-by: Sasha Levin --- drivers/usb/gadget/function/u_serial.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c index 510a54f88963..5d7d0f2e80a5 100644 --- a/drivers/usb/gadget/function/u_serial.c +++ b/drivers/usb/gadget/function/u_serial.c @@ -715,8 +715,10 @@ static int gs_start_io(struct gs_port *port) port->n_read = 0; started = gs_start_rx(port); - /* unblock any pending writes into our circular buffer */ if (started) { + gs_start_tx(port); + /* Unblock any pending writes into our circular buffer, in case + * we didn't in gs_start_tx() */ tty_wakeup(port->port.tty); } else { gs_free_requests(ep, head, &port->read_allocated); -- 2.34.1