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Commit af9b897e authored by Alan Cox's avatar Alan Cox Committed by Linus Torvalds
Browse files

[PATCH] tty layer comment the locking assumptions and functions somewhat 



Doesn't fix them but does show up some interesting areas that need review
and fixing.

Signed-off-by: default avatarAlan Cox <alan@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 9c275a83

drivers/char/tty_io.c

+658 −60

File changed.

Preview size limit exceeded, changes collapsed.

drivers/char/tty_ioctl.c

+57 −2
Original line number Diff line number Diff line
@@ -36,6 +36,18 @@ 
#define TERMIOS_WAIT	2

#define TERMIOS_TERMIO	4





/**

 *	tty_wait_until_sent	-	wait for I/O to finish

 *	@tty: tty we are waiting for

 *	@timeout: how long we will wait

 *

 *	Wait for characters pending in a tty driver to hit the wire, or

 *	for a timeout to occur (eg due to flow control)

 *

 *	Locking: none

 */



void tty_wait_until_sent(struct tty_struct * tty, long timeout)

{

	DECLARE_WAITQUEUE(wait, current);
@@ -94,6 +106,18 @@ static void unset_locked_termios(struct termios *termios, 
			old->c_cc[i] : termios->c_cc[i];

}



/**

 *	change_termios		-	update termios values

 *	@tty: tty to update

 *	@new_termios: desired new value

 *

 *	Perform updates to the termios values set on this terminal. There

 *	is a bit of layering violation here with n_tty in terms of the

 *	internal knowledge of this function.

 *

 *	Locking: termios_sem

 */



static void change_termios(struct tty_struct * tty, struct termios * new_termios)

{

	int canon_change;
@@ -155,6 +179,19 @@ static void change_termios(struct tty_struct * tty, struct termios * new_termios 
	up(&tty->termios_sem);

}



/**

 *	set_termios		-	set termios values for a tty

 *	@tty: terminal device

 *	@arg: user data

 *	@opt: option information

 *

 *	Helper function to prepare termios data and run neccessary other

 *	functions before using change_termios to do the actual changes.

 *

 *	Locking:

 *		Called functions take ldisc and termios_sem locks

 */



static int set_termios(struct tty_struct * tty, void __user *arg, int opt)

{

	struct termios tmp_termios;
@@ -284,6 +321,17 @@ static void set_sgflags(struct termios * termios, int flags) 
	}

}



/**

 *	set_sgttyb		-	set legacy terminal values

 *	@tty: tty structure

 *	@sgttyb: pointer to old style terminal structure

 *

 *	Updates a terminal from the legacy BSD style terminal information

 *	structure.

 *

 *	Locking: termios_sem

 */



static int set_sgttyb(struct tty_struct * tty, struct sgttyb __user * sgttyb)

{

	int retval;
@@ -369,9 +417,16 @@ static int set_ltchars(struct tty_struct * tty, struct ltchars __user * ltchars) 
}

#endif



/*

 * Send a high priority character to the tty.

/**

 *	send_prio_char		-	send priority character

 *

 *	Send a high priority character to the tty even if stopped

 *

 *	Locking: none

 *

 *	FIXME: overlapping calls with start/stop tty lose state of tty

 */



static void send_prio_char(struct tty_struct *tty, char ch)

{

	int	was_stopped = tty->stopped;