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[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: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Alan Cox 2006-08-27 01:24:01 -07:00 committed by Linus Torvalds
parent 9c275a8391
commit af9b897ee6
2 changed files with 715 additions and 62 deletions
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658
drivers/char/tty_io.c
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File diff suppressed because it is too large Load Diff

59
drivers/char/tty_ioctl.c
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@ -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;