TTY: add port -> tty link (967fab69) · Commits · 戴 / test

For that purpose we have to temporarily introduce a second tty back pointer into tty_port. It is because serial layer, and maybe others, still do not use tty_port_tty_set/get. So that we cannot set the tty_port->tty to NULL at will now. Yes, the fix would be to convert whole serial layer and all its users to tty_port_tty_set/get. However we are in the process of removing the need of tty in most of the call sites, so this would lead to a duplicated work. Instead we have now tty_port->itty (internal tty) which will be used only in flush_to_ldisc. For that one it is ensured that itty is valid wherever the work is run. IOW, the work is synchronously cancelled before we set itty to NULL and also before hangup is processed. After we need only tty_port and not tty_struct in most code, this shall be changed to tty_port_tty_set/get and itty removed completely. Signed-off-by:

Jiri Slaby <jslaby@suse.cz> Acked-by:

Alan Cox <alan@linux.intel.com> Signed-off-by:

Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/pty.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -345,6 +345,7 @@ static int pty_common_install(struct tty_driver driver, struct tty_struct tty,
		tty_port_init(ports[1]);
		o_tty->port = ports[0];
		tty->port = ports[1];
		o_tty->port->itty = o_tty;

		tty_driver_kref_get(driver);
		tty->count++;
		@@ -371,6 +372,7 @@ static void pty_unix98_shutdown(struct tty_struct *tty)

		static void pty_cleanup(struct tty_struct *tty)
		{
		tty->port->itty = NULL;
		kfree(tty->port);
		}

drivers/tty/tty_io.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -1417,6 +1417,8 @@ struct tty_struct tty_init_dev(struct tty_driver driver, int idx)
		"%s: %s driver does not set tty->port. This will crash the kernel later. Fix the driver!\n",
		__func__, tty->driver->name);

		tty->port->itty = tty;

		/*
		* Structures all installed ... call the ldisc open routines.
		* If we fail here just call release_tty to clean up. No need
		@@ -1552,6 +1554,7 @@ static void release_tty(struct tty_struct *tty, int idx)
		tty->ops->shutdown(tty);
		tty_free_termios(tty);
		tty_driver_remove_tty(tty->driver, tty);
		tty->port->itty = NULL;

		if (tty->link)
		tty_kref_put(tty->link);

include/linux/tty.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -189,6 +189,7 @@ struct tty_port_operations {

		struct tty_port {
		struct tty_struct tty; / Back pointer */
		struct tty_struct itty; / internal back ptr */
		const struct tty_port_operations ops; / Port operations */
		spinlock_t lock; /* Lock protecting tty field */
		int blocked_open; /* Waiting to open */

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