korg/linux
0
0
Fork 0
mirror of https://mirrors.bfsu.edu.cn/git/linux.git synced 2024-12-12 13:34:10 +08:00
Code Issues Packages Projects Releases Wiki Activity

tty: n_gsm: fix wrong queuing behavior in gsm_dlci_data_output()

Browse Source 
1) The function drains the fifo for the given user tty/DLCI without
considering 'TX_THRESH_HI' and different to gsm_dlci_data_output_framed(),
which moves only one packet from the user side to the internal transmission
queue. We can only handle one packet at a time here if we want to allow
DLCI priority handling in gsm_dlci_data_sweep() to avoid link starvation.
2) Furthermore, the additional header octet from convergence layer type 2
is not counted against MTU. It is part of the UI/UIH frame message which
needs to be limited to MTU. Hence, it is wrong not to consider this octet.
3) Finally, the waiting user tty is not informed about freed space in its
send queue.

Take at most one packet worth of data out of the DLCI fifo to fix 1).
Limit the max user data size per packet to MTU - 1 in case of convergence
layer type 2 to leave space for the control signal octet which is added in
the later part of the function. This fixes 2).
Add tty_port_tty_wakeup() to wake up the user tty if new write space has
been made available to fix 3).

Fixes: 268e526b93 ("tty/n_gsm: avoid fifo overflow in gsm_dlci_data_output")
Signed-off-by: Daniel Starke <daniel.starke@siemens.com>
Link: https://lore.kernel.org/r/20220701061652.39604-3-daniel.starke@siemens.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Starke 2022-07-01 08:16:46 +02:00 committed by Greg Kroah-Hartman
parent 01aecd9171
commit 556fc8ac06
1 changed files with 39 additions and 29 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

42
drivers/tty/n_gsm.c
View File

@ -886,41 +886,51 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
{
struct gsm_msg *msg;
u8 *dp;
int len, total_size, size;
int h = dlci->adaption - 1;
int h, len, size;
/* for modem bits without break data */
h = ((dlci->adaption == 1) ? 0 : 1);
total_size = 0;
while (1) {
len = kfifo_len(&dlci->fifo);
if (len == 0)
return total_size;
return 0;
/* MTU/MRU count only the data bits */
if (len > gsm->mtu)
len = gsm->mtu;
/* MTU/MRU count only the data bits but watch adaption mode */
if ((len + h) > gsm->mtu)
len = gsm->mtu - h;
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 == NULL)
* get stuck with no work outstanding and no buffer free
*/
if (!msg)
return -ENOMEM;
dp = msg->data;
switch (dlci->adaption) {
case 1: /* Unstructured */
break;
case 2: /* Unstructed with modem bits.
Always one byte as we never send inline break data */
case 2: /* Unstructured with modem bits.
* Always one byte as we never send inline break data
*/
*dp++ = (gsm_encode_modem(dlci) << 1) | EA;
break;
default:
pr_err("%s: unsupported adaption %d\n", __func__,
dlci->adaption);
break;
}
WARN_ON(kfifo_out_locked(&dlci->fifo, dp , len, &dlci->lock) != len);
WARN_ON(len != kfifo_out_locked(&dlci->fifo, dp, len,
&dlci->lock));
/* Notify upper layer about available send space. */
tty_port_tty_wakeup(&dlci->port);
__gsm_data_queue(dlci, msg);
total_size += size;
}
/* Bytes of data we used up */
return total_size;
return size;
}
/**