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authorSascha Hauer2017-05-31 08:19:05 +0200
committerGreg Kroah-Hartman2017-06-03 18:48:52 +0900
commit71e0779153968c79038a8ed53610d69624115fca (patch)
tree20a4d97d4ba762851fb33c61597d8efaa0371a60 /drivers/tty
parente279e6d98e0cf2c2fe008b3c29042b92f0e17b1d (diff)
tty: n_gsm: do not send/receive in ldisc close path
gsm_cleanup_mux() is called in the line discipline close path which is called at tty_release() time. At this stage the tty is no longer operational enough to send any frames. Sending close frames is therefore not possible and waiting for their answers always times out. This patch removes sending close messages and waiting for their answers from the tty_release path. This patch makes explicit what previously implicitly had been the case already: We are not able to tell the modem that we are about to close the multiplexer on our side. This means the modem will stay in multiplexer mode and re-establishing the multiplexer later fails. The only way for userspace to work around this is to manually send a close frame in N_TTY mode after closing the mux. Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/n_gsm.c54
1 files changed, 35 insertions, 19 deletions
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 2667a205a5ab..363a8ca824ad 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2015,6 +2015,33 @@ static void gsm_error(struct gsm_mux *gsm,
gsm->io_error++;
}
+static int gsm_disconnect(struct gsm_mux *gsm)
+{
+ struct gsm_dlci *dlci = gsm->dlci[0];
+ struct gsm_control *gc;
+
+ if (!dlci)
+ return 0;
+
+ /* In theory disconnecting DLCI 0 is sufficient but for some
+ modems this is apparently not the case. */
+ gc = gsm_control_send(gsm, CMD_CLD, NULL, 0);
+ if (gc)
+ gsm_control_wait(gsm, gc);
+
+ del_timer_sync(&gsm->t2_timer);
+ /* Now we are sure T2 has stopped */
+
+ gsm_dlci_begin_close(dlci);
+ wait_event_interruptible(gsm->event,
+ dlci->state == DLCI_CLOSED);
+
+ if (signal_pending(current))
+ return -EINTR;
+
+ return 0;
+}
+
/**
* gsm_cleanup_mux - generic GSM protocol cleanup
* @gsm: our mux
@@ -2029,7 +2056,6 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm)
int i;
struct gsm_dlci *dlci = gsm->dlci[0];
struct gsm_msg *txq, *ntxq;
- struct gsm_control *gc;
gsm->dead = 1;
@@ -2045,21 +2071,11 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm)
if (i == MAX_MUX)
return;
- /* In theory disconnecting DLCI 0 is sufficient but for some
- modems this is apparently not the case. */
- if (dlci) {
- gc = gsm_control_send(gsm, CMD_CLD, NULL, 0);
- if (gc)
- gsm_control_wait(gsm, gc);
- }
del_timer_sync(&gsm->t2_timer);
/* Now we are sure T2 has stopped */
- if (dlci) {
+ if (dlci)
dlci->dead = 1;
- gsm_dlci_begin_close(dlci);
- wait_event_interruptible(gsm->event,
- dlci->state == DLCI_CLOSED);
- }
+
/* Free up any link layer users */
mutex_lock(&gsm->mutex);
for (i = 0; i < NUM_DLCI; i++)
@@ -2519,12 +2535,12 @@ static int gsmld_config(struct tty_struct *tty, struct gsm_mux *gsm,
*/
if (need_close || need_restart) {
- gsm_dlci_begin_close(gsm->dlci[0]);
- /* This will timeout if the link is down due to N2 expiring */
- wait_event_interruptible(gsm->event,
- gsm->dlci[0]->state == DLCI_CLOSED);
- if (signal_pending(current))
- return -EINTR;
+ int ret;
+
+ ret = gsm_disconnect(gsm);
+
+ if (ret)
+ return ret;
}
if (need_restart)
gsm_cleanup_mux(gsm);