[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>
diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index f19cf9d..4ad47d3 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -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 @@
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 @@
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 @@
}
}
+/**
+ * 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 @@
}
#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;