From: Daniel Starke daniel.starke@siemens.com
[ Upstream commit c568f7086c6e771c77aad13d727c70ef70e07243 ]
The current implementation does not handle the situation that no data is in the internal queue and needs to be sent out while the user tty fifo is full. Add a timer that moves more data from user tty down to the internal queue which is then serialized on the ldisc. This timer is triggered if no data was moved from a user tty to the internal queue within 10 * T1.
Fixes: e1eaea46bb40 ("tty: n_gsm line discipline") Signed-off-by: Daniel Starke daniel.starke@siemens.com Link: https://lore.kernel.org/r/20220701061652.39604-4-daniel.starke@siemens.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/tty/n_gsm.c | 43 +++++++++++++++++++++++++++++++++++-------- 1 file changed, 35 insertions(+), 8 deletions(-)
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index 658d8f6e3a7d..27e72c623afb 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -244,6 +244,7 @@ struct gsm_mux { struct list_head tx_list; /* Pending data packets */
/* Control messages */ + struct timer_list kick_timer; /* Kick TX queuing on timeout */ struct timer_list t2_timer; /* Retransmit timer for commands */ int cretries; /* Command retry counter */ struct gsm_control *pending_cmd;/* Our current pending command */ @@ -850,6 +851,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg) list_add_tail(&msg->list, &gsm->tx_list); gsm->tx_bytes += msg->len; gsm_data_kick(gsm, dlci); + mod_timer(&gsm->kick_timer, jiffies + 10 * gsm->t1 * HZ / 100); }
/** @@ -902,9 +904,6 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci) size = len + h;
msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype); - /* FIXME: need a timer or something to kick this so it can't - * get stuck with no work outstanding and no buffer free - */ if (!msg) return -ENOMEM; dp = msg->data; @@ -981,9 +980,6 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
size = len + overhead; msg = gsm_data_alloc(gsm, dlci->addr, size, gsm->ftype); - - /* FIXME: need a timer or something to kick this so it can't - get stuck with no work outstanding and no buffer free */ if (msg == NULL) { skb_queue_tail(&dlci->skb_list, dlci->skb); dlci->skb = NULL; @@ -1079,9 +1075,9 @@ static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci, * renegotiate DLCI priorities with optional stuff. Needs optimising. */
-static void gsm_dlci_data_sweep(struct gsm_mux *gsm) +static int gsm_dlci_data_sweep(struct gsm_mux *gsm) { - int len; + int len, ret = 0; /* Priority ordering: We should do priority with RR of the groups */ int i = 1;
@@ -1104,7 +1100,11 @@ static void gsm_dlci_data_sweep(struct gsm_mux *gsm) /* DLCI empty - try the next */ if (len == 0) i++; + else + ret++; } + + return ret; }
/** @@ -1823,6 +1823,30 @@ static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len) } }
+/** + * gsm_kick_timer - transmit if possible + * @t: timer contained in our gsm object + * + * Transmit data from DLCIs if the queue is empty. We can't rely on + * a tty wakeup except when we filled the pipe so we need to fire off + * new data ourselves in other cases. + */ +static void gsm_kick_timer(struct timer_list *t) +{ + struct gsm_mux *gsm = from_timer(gsm, t, kick_timer); + unsigned long flags; + int sent = 0; + + spin_lock_irqsave(&gsm->tx_lock, flags); + /* If we have nothing running then we need to fire up */ + if (gsm->tx_bytes < TX_THRESH_LO) + sent = gsm_dlci_data_sweep(gsm); + spin_unlock_irqrestore(&gsm->tx_lock, flags); + + if (sent && debug & 4) + pr_info("%s TX queue stalled\n", __func__); +} + /* * Allocate/Free DLCI channels */ @@ -2278,6 +2302,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc) }
/* Finish outstanding timers, making sure they are done */ + del_timer_sync(&gsm->kick_timer); del_timer_sync(&gsm->t2_timer);
/* Free up any link layer users and finally the control channel */ @@ -2310,6 +2335,7 @@ static int gsm_activate_mux(struct gsm_mux *gsm) struct gsm_dlci *dlci; int ret;
+ timer_setup(&gsm->kick_timer, gsm_kick_timer, 0); timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0); init_waitqueue_head(&gsm->event); spin_lock_init(&gsm->control_lock); @@ -2714,6 +2740,7 @@ static int gsmld_open(struct tty_struct *tty)
gsmld_attach_gsm(tty, gsm);
+ timer_setup(&gsm->kick_timer, gsm_kick_timer, 0); timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
return 0;