TTY: um/line, use tty from tty_port

This means switching to the tty refcounted model so that we will not
race with interrupts.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Jeff Dike <jdike@addtoit.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: user-mode-linux-devel@lists.sourceforge.net
Signed-off-by: Richard Weinberger <richard@nod.at>

3 files changed, 21 insertions, 9 deletions

diff --git a/arch/um/drivers/chan_kern.c b/arch/um/drivers/chan_kern.c
index 45e248c2f43c..87eebfe03c61 100644
--- a/arch/um/drivers/chan_kern.c
+++ b/arch/um/drivers/chan_kern.c
@@ -150,9 +150,11 @@ void chan_enable_winch(struct chan *chan, struct tty_struct *tty)
 static void line_timer_cb(struct work_struct *work)
 {
         struct line *line = container_of(work, struct line, task.work);
+        struct tty_struct *tty = tty_port_tty_get(&line->port);
 
         if (!line->throttled)
-                chan_interrupt(line, line->tty, line->driver->read_irq);
+                chan_interrupt(line, tty, line->driver->read_irq);
+        tty_kref_put(tty);
 }
 
 int enable_chan(struct line *line)
diff --git a/arch/um/drivers/line.c b/arch/um/drivers/line.c
index 482a7bd4a64c..fb6e4ea09921 100644
--- a/arch/um/drivers/line.c
+++ b/arch/um/drivers/line.c
@@ -19,9 +19,11 @@ static irqreturn_t line_interrupt(int irq, void *data)
 {
         struct chan *chan = data;
         struct line *line = chan->line;
+        struct tty_struct *tty = tty_port_tty_get(&line->port);
 
         if (line)
-                chan_interrupt(line, line->tty, irq);
+                chan_interrupt(line, tty, irq);
+        tty_kref_put(tty);
         return IRQ_HANDLED;
 }
 
@@ -333,7 +335,7 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
 {
         struct chan *chan = data;
         struct line *line = chan->line;
-        struct tty_struct *tty = line->tty;
+        struct tty_struct *tty;
         int err;
 
         /*
@@ -352,10 +354,13 @@ static irqreturn_t line_write_interrupt(int irq, void *data)
         }
         spin_unlock(&line->lock);
 
+        tty = tty_port_tty_get(&line->port);
         if (tty == NULL)
                 return IRQ_NONE;
 
         tty_wakeup(tty);
+        tty_kref_put(tty);
+
         return IRQ_HANDLED;
 }
 
@@ -409,7 +414,7 @@ int line_open(struct line *lines, struct tty_struct *tty)
 
         BUG_ON(tty->driver_data);
         tty->driver_data = line;
-        line->tty = tty;
+        tty_port_tty_set(&line->port, tty);
 
         err = enable_chan(line);
         if (err) /* line_close() will be called by our caller */
@@ -449,7 +454,7 @@ void line_close(struct tty_struct *tty, struct file * filp)
         if (--line->port.count)
                 goto out_unlock;
 
-        line->tty = NULL;
+        tty_port_tty_set(&line->port, NULL);
         tty->driver_data = NULL;
 
         if (line->sigio) {
@@ -610,9 +615,15 @@ int line_get_config(char *name, struct line *lines, unsigned int num, char *str,
         mutex_lock(&line->count_lock);
         if (!line->valid)
                 CONFIG_CHUNK(str, size, n, "none", 1);
-        else if (line->tty == NULL)
-                CONFIG_CHUNK(str, size, n, line->init_str, 1);
-        else n = chan_config_string(line, str, size, error_out);
+        else {
+                struct tty_struct *tty = tty_port_tty_get(&line->port);
+                if (tty == NULL) {
+                        CONFIG_CHUNK(str, size, n, line->init_str, 1);
+                } else {
+                        n = chan_config_string(line, str, size, error_out);
+                        tty_kref_put(tty);
+                }
+        }
         mutex_unlock(&line->count_lock);
 
         return n;
diff --git a/arch/um/drivers/line.h b/arch/um/drivers/line.h
index 0e06a1f441d7..5b3d4fbdec18 100644
--- a/arch/um/drivers/line.h
+++ b/arch/um/drivers/line.h
@@ -33,7 +33,6 @@ struct line_driver {
 
 struct line {
         struct tty_port port;
-        struct tty_struct *tty;
         struct mutex count_lock;
         int valid;