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tty: n_gsm: fix missing timer to handle stalled links

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[ 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>
This commit is contained in:
Daniel Starke 2022-07-01 08:16:47 +02:00 committed by Greg Kroah-Hartman
parent 1018139cbb
commit dd37f65738
1 changed files with 35 additions and 8 deletions
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43
drivers/tty/n_gsm.c
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@ -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;
}
/**
@ -1837,6 +1837,30 @@ 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
*/
@ -2326,6 +2350,7 @@ 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 */
@ -2358,6 +2383,7 @@ 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);
@ -2762,6 +2788,7 @@ 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;