um: Use tty_port in SIGWINCH handler

The tty below tty_port might get destroyed by the tty layer
while we hold a reference to it.
So we have to carry tty_port around...

Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/chan.h

@@ -37,7 +37,7 @@ extern int console_write_chan(struct chan *chan, const char *buf,
 extern int console_open_chan(struct line *line, struct console *co);
 extern void deactivate_chan(struct chan *chan, int irq);
 extern void reactivate_chan(struct chan *chan, int irq);
-extern void chan_enable_winch(struct chan *chan, struct tty_struct *tty);
+extern void chan_enable_winch(struct chan *chan, struct tty_port *port);
 extern int enable_chan(struct line *line);
 extern void close_chan(struct line *line);
 extern int chan_window_size(struct line *line, 

arch/um/drivers/chan_kern.c

@@ -122,10 +122,10 @@ static int open_chan(struct list_head *chans)
 	return err;
 }
 
-void chan_enable_winch(struct chan *chan, struct tty_struct *tty)
+void chan_enable_winch(struct chan *chan, struct tty_port *port)
 {
 	if (chan && chan->primary && chan->ops->winch)
-		register_winch(chan->fd, tty);
+		register_winch(chan->fd, port);
 }
 
 static void line_timer_cb(struct work_struct *work)

arch/um/drivers/chan_user.c

@@ -216,7 +216,7 @@ static int winch_thread(void *arg)
 	}
 }
 
-static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out,
+static int winch_tramp(int fd, struct tty_port *port, int *fd_out,
 		       unsigned long *stack_out)
 {
 	struct winch_data data;
@@ -271,7 +271,7 @@ static int winch_tramp(int fd, struct tty_struct *tty, int *fd_out,
 	return err;
 }
 
-void register_winch(int fd, struct tty_struct *tty)
+void register_winch(int fd, struct tty_port *port)
 {
 	unsigned long stack;
 	int pid, thread, count, thread_fd = -1;
@@ -281,17 +281,17 @@ void register_winch(int fd, struct tty_struct *tty)
 		return;
 
 	pid = tcgetpgrp(fd);
-	if (is_skas_winch(pid, fd, tty)) {
-		register_winch_irq(-1, fd, -1, tty, 0);
+	if (is_skas_winch(pid, fd, port)) {
+		register_winch_irq(-1, fd, -1, port, 0);
 		return;
 	}
 
 	if (pid == -1) {
-		thread = winch_tramp(fd, tty, &thread_fd, &stack);
+		thread = winch_tramp(fd, port, &thread_fd, &stack);
 		if (thread < 0)
 			return;
 
-		register_winch_irq(thread_fd, fd, thread, tty, stack);
+		register_winch_irq(thread_fd, fd, thread, port, stack);
 
 		count = write(thread_fd, &c, sizeof(c));
 		if (count != sizeof(c))

arch/um/drivers/chan_user.h

@@ -38,10 +38,10 @@ extern int generic_window_size(int fd, void *unused, unsigned short *rows_out,
 			       unsigned short *cols_out);
 extern void generic_free(void *data);
 
-struct tty_struct;
-extern void register_winch(int fd,  struct tty_struct *tty);
+struct tty_port;
+extern void register_winch(int fd,  struct tty_port *port);
 extern void register_winch_irq(int fd, int tty_fd, int pid,
-			       struct tty_struct *tty, unsigned long stack);
+			       struct tty_port *port, unsigned long stack);
 
 #define __channel_help(fn, prefix) \
 __uml_help(fn, prefix "[0-9]*=<channel description>\n" \

arch/um/drivers/line.c

@@ -305,7 +305,7 @@ static int line_activate(struct tty_port *port, struct tty_struct *tty)
 		return ret;
 
 	if (!line->sigio) {
-		chan_enable_winch(line->chan_out, tty);
+		chan_enable_winch(line->chan_out, port);
 		line->sigio = 1;
 	}
 
@@ -603,7 +603,7 @@ struct winch {
 	int fd;
 	int tty_fd;
 	int pid;
-	struct tty_struct *tty;
+	struct tty_port *port;
 	unsigned long stack;
 	struct work_struct work;
 };
@@ -657,22 +657,23 @@ static irqreturn_t winch_interrupt(int irq, void *data)
 			goto out;
 		}
 	}
-	tty = winch->tty;
+	tty = tty_port_tty_get(winch->port);
 	if (tty != NULL) {
 		line = tty->driver_data;
 		if (line != NULL) {
 			chan_window_size(line, &tty->winsize.ws_row,
 					 &tty->winsize.ws_col);
 			kill_pgrp(tty->pgrp, SIGWINCH, 1);
 		}
+		tty_kref_put(tty);
 	}
  out:
 	if (winch->fd != -1)
 		reactivate_fd(winch->fd, WINCH_IRQ);
 	return IRQ_HANDLED;
 }
 
-void register_winch_irq(int fd, int tty_fd, int pid, struct tty_struct *tty,
+void register_winch_irq(int fd, int tty_fd, int pid, struct tty_port *port,
 			unsigned long stack)
 {
 	struct winch *winch;
@@ -687,7 +688,7 @@ void register_winch_irq(int fd, int tty_fd, int pid, struct tty_struct *tty,
 				   .fd  	= fd,
 				   .tty_fd 	= tty_fd,
 				   .pid  	= pid,
-				   .tty 	= tty,
+				   .port 	= port,
 				   .stack	= stack });
 
 	if (um_request_irq(WINCH_IRQ, fd, IRQ_READ, winch_interrupt,
@@ -716,15 +717,18 @@ static void unregister_winch(struct tty_struct *tty)
 {
 	struct list_head *ele, *next;
 	struct winch *winch;
+	struct tty_struct *wtty;
 
 	spin_lock(&winch_handler_lock);
 
 	list_for_each_safe(ele, next, &winch_handlers) {
 		winch = list_entry(ele, struct winch, list);
-		if (winch->tty == tty) {
+		wtty = tty_port_tty_get(winch->port);
+		if (wtty == tty) {
 			free_winch(winch);
 			break;
 		}
+		tty_kref_put(wtty);
 	}
 	spin_unlock(&winch_handler_lock);
 }