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tty: n_gsm: fix flow control handling in tx path

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[ Upstream commit 59ff0680ecbfec742b1e0381e7cc46b41eb06647 ]

The current implementation constipates all transmission paths during flow
control except for flow control frames. However, these may not be located
at the beginning of the transmission queue of the control channel.
Ensure that flow control frames in the transmission queue for the control
channel are always handled even if constipated by skipping through other
messages.

Fixes: 0af021678d5d ("tty: n_gsm: fix deadlock and link starvation in outgoing data path")
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220707113223.3685-3-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Daniel Starke 2022-07-07 13:32:22 +02:00 committed by Greg Kroah-Hartman
parent e5e39b5244
commit 96114c3b26
1 changed files with 1 additions and 1 deletions
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2
drivers/tty/n_gsm.c
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@ -891,7 +891,7 @@ static int gsm_data_kick(struct gsm_mux *gsm)
/* Serialize control messages and control channel messages first */
list_for_each_entry_safe(msg, nmsg, &gsm->tx_ctrl_list, list) {
if (gsm->constipated && !gsm_is_flow_ctrl_msg(msg))
return -EAGAIN;
continue;
ret = gsm_send_packet(gsm, msg);
switch (ret) {
case -ENOSPC: