The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 1adf6fee58ca25fb6720b8d34c919dcf5425cc9c Mon Sep 17 00:00:00 2001 From: Daniel Starke daniel.starke@siemens.com Date: Thu, 14 Apr 2022 02:42:19 -0700 Subject: [PATCH] tty: n_gsm: fix missing tty wakeup in convergence layer type 2

gsm_control_modem() informs the virtual tty that more data can be written after receiving a control signal octet via modem status command (MSC). However, gsm_dlci_data() fails to do the same after receiving a control signal octet from the convergence layer type 2 header. Add tty_wakeup() in gsm_dlci_data() for convergence layer type 2 to fix this.

Fixes: e1eaea46bb40 ("tty: n_gsm line discipline") Cc: stable@vger.kernel.org Signed-off-by: Daniel Starke daniel.starke@siemens.com Link: https://lore.kernel.org/r/20220414094225.4527-14-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 23418ee93156..f3fb66be8513 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -1615,6 +1615,7 @@ static void gsm_dlci_data(struct gsm_dlci *dlci, const u8 *data, int clen) tty = tty_port_tty_get(port); if (tty) { gsm_process_modem(tty, dlci, modem, slen); + tty_wakeup(tty); tty_kref_put(tty); } fallthrough;