Revert "n_gsm: race between ld close and gsmtty open"

This reverts commit c284ee2cf12b55fa8496b2d098bf0938688f1c1c.  Turns out
the locking was incorrect.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Chao Bi <chao.bi@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 069bfd6544856fdcfdf90f7ea6f7f5da774b899a..c0f76da553042db2f3eadb91cfb9ff08bc60e43d 100644 (file)
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2054,11 +2054,9 @@ void gsm_cleanup_mux(struct gsm_mux *gsm)
                                        dlci->state == DLCI_CLOSED);
        }
        /* Free up any link layer users */
-       spin_lock(&gsm->lock);
        for (i = 0; i < NUM_DLCI; i++)
                if (gsm->dlci[i])
                        gsm_dlci_release(gsm->dlci[i]);
-       spin_unlock(&gsm->lock);
        /* Now wipe the queues */
        list_for_each_entry_safe(txq, ntxq, &gsm->tx_list, list)
                kfree(txq);
@@ -2911,33 +2909,23 @@ static int gsmtty_install(struct tty_driver *driver, struct tty_struct *tty)
        This is ok from a locking
        perspective as we don't have to worry about this
        if DLCI0 is lost */
-       spin_lock(&gsm->lock);
-       if (gsm->dlci[0] && gsm->dlci[0]->state != DLCI_OPEN) {
-               spin_unlock(&gsm->lock);
+       if (gsm->dlci[0] && gsm->dlci[0]->state != DLCI_OPEN)
                return -EL2NSYNC;
-       }
        dlci = gsm->dlci[line];
        if (dlci == NULL) {
                alloc = true;
                dlci = gsm_dlci_alloc(gsm, line);
        }
-       if (dlci == NULL) {
-               spin_unlock(&gsm->lock);
+       if (dlci == NULL)
                return -ENOMEM;
-       }
        ret = tty_port_install(&dlci->port, driver, tty);
        if (ret) {
                if (alloc)
                        dlci_put(dlci);
-               spin_unlock(&gsm->lock);
                return ret;
        }
 
-       dlci_get(dlci);
-       dlci_get(gsm->dlci[0]);
-       mux_get(gsm);
        tty->driver_data = dlci;
-       spin_unlock(&gsm->lock);
 
        return 0;
 }
@@ -2948,6 +2936,9 @@ static int gsmtty_open(struct tty_struct *tty, struct file *filp)
        struct tty_port *port = &dlci->port;
 
        port->count++;
+       dlci_get(dlci);
+       dlci_get(dlci->gsm->dlci[0]);
+       mux_get(dlci->gsm);
        tty_port_tty_set(port, tty);
 
        dlci->modem_rx = 0;
@@ -2974,7 +2965,7 @@ static void gsmtty_close(struct tty_struct *tty, struct file *filp)
        mutex_unlock(&dlci->mutex);
        gsm = dlci->gsm;
        if (tty_port_close_start(&dlci->port, tty, filp) == 0)
-               return;
+               goto out;
        gsm_dlci_begin_close(dlci);
        if (test_bit(ASYNCB_INITIALIZED, &dlci->port.flags)) {
                if (C_HUPCL(tty))
@@ -2982,7 +2973,10 @@ static void gsmtty_close(struct tty_struct *tty, struct file *filp)
        }
        tty_port_close_end(&dlci->port, tty);
        tty_port_tty_set(&dlci->port, NULL);
-       return;
+out:
+       dlci_put(dlci);
+       dlci_put(gsm->dlci[0]);
+       mux_put(gsm);
 }
 
 static void gsmtty_hangup(struct tty_struct *tty)
@@ -3159,16 +3153,6 @@ static int gsmtty_break_ctl(struct tty_struct *tty, int state)
        return gsmtty_modem_update(dlci, encode);
 }
 
-static void gsmtty_remove(struct tty_driver *driver, struct tty_struct *tty)
-{
-       struct gsm_dlci *dlci = tty->driver_data;
-       struct gsm_mux *gsm = dlci->gsm;
-
-       dlci_put(dlci);
-       dlci_put(gsm->dlci[0]);
-       mux_put(gsm);
-       driver->ttys[tty->index] = NULL;
-}
 
 /* Virtual ttys for the demux */
 static const struct tty_operations gsmtty_ops = {
@@ -3188,7 +3172,6 @@ static const struct tty_operations gsmtty_ops = {
        .tiocmget               = gsmtty_tiocmget,
        .tiocmset               = gsmtty_tiocmset,
        .break_ctl              = gsmtty_break_ctl,
-       .remove                 = gsmtty_remove,
 };