From: Sergey Organov <sorganov@gmail.com>
To: linux-usb@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Felipe Balbi" <balbi@kernel.org>,
"Michał Mirosław" <mirq-linux@rere.qmqm.pl>,
linux-serial@vger.kernel.org
Subject: [PATCH v3] usb: gadget: serial: fix Tx stall after buffer overflow
Date: Wed, 29 Jan 2020 14:21:46 +0300 [thread overview]
Message-ID: <87sgjyzewl.fsf@osv.gnss.ru> (raw)
In-Reply-To: <87pnfi8xc2.fsf@osv.gnss.ru> (Sergey Organov's message of "Fri, 17 Jan 2020 08:29:33 +0300")
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 <sorganov@gmail.com>
Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
---
Changes in v3:
- Add Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Changes in v2:
- Add comment to document why tty_wakeup() is kept in place
- Don't add debug print
- Remove NOTE from description
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 f986e5c..8167d37 100644
--- a/drivers/usb/gadget/function/u_serial.c
+++ b/drivers/usb/gadget/function/u_serial.c
@@ -561,8 +561,10 @@ 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);
--
2.10.0.1.g57b01a3
prev parent reply other threads:[~2020-01-29 11:21 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-17 5:29 [PATCH] usb: gadget: serial: fix Tx stall after buffer overflow Sergey Organov
2020-01-17 20:34 ` Michał Mirosław
2020-01-20 6:06 ` Sergey Organov
2020-01-20 9:45 ` Michał Mirosław
2020-01-20 13:38 ` Sergey Organov
2020-01-20 14:05 ` Michał Mirosław
2020-01-21 6:41 ` Sergey Organov
2020-01-21 4:42 ` [PATCH v2] " Sergey Organov
2020-01-21 16:39 ` Michał Mirosław
2020-01-29 11:21 ` Sergey Organov [this message]
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