[PATCH 04/45] tty: vt: expect valid vc when in tty ops

Jiri Slaby (SUSE)
2024-01-18T07:58:11Z

At least since commits feebed6515a1 ("tty: shutdown method") and
bc1e99d93f09 ("TTY: vt, add ->install"), tty->driver_data in vc is
expected to be set since tty_operations::install() till ::cleanup().

So the checks of !tty->driver_data (aka !vc) in:
* vc_do_resize() by tty -> ioctl(TIOCSWINSZ) -> vt_resize()
* do_con_write() by tty -> tty_operations::write()/::put_char()
* con_flush_chars() by tty -> ::flush_chars()
are all superfluous. And also, holding a console lock is not needed to
fetch tty->driver_data.

Note there is even a stale comment in con_flush_chars() about a race
between that and con_close(). But con_close() does not set
tty->driver_data to NULL for years already.

Drop all these in a hope I am not terribly mistaken.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
drivers/tty/vt/vt.c | 19 +++----------------
1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c
index 55ce6cdecbca..e131edea00da 100644
--- a/drivers/tty/vt/vt.c
+++ b/drivers/tty/vt/vt.c
@@ -1154,9 +1154,6 @@ static int vc_do_resize(struct tty_struct *tty, struct vc_data *vc,

WARN_CONSOLE_UNLOCKED();

- if (!vc)
- return -ENXIO;
-
user = vc->vc_resize_user;
vc->vc_resize_user = 0;

@@ -2852,7 +2849,7 @@ static int do_con_write(struct tty_struct *tty, const u8 *buf, int count)
};
int c, tc, n = 0;
unsigned int currcons;
- struct vc_data *vc;
+ struct vc_data *vc = tty->driver_data;
struct vt_notifier_param param;
bool rescan;

@@ -2860,13 +2857,6 @@ static int do_con_write(struct tty_struct *tty, const u8 *buf, int count)
return count;

console_lock();
- vc = tty->driver_data;
- if (vc == NULL) {
- pr_err("vt: argh, driver_data is NULL !\n");
- console_unlock();
- return 0;
- }
-
currcons = vc->vc_num;
if (!vc_cons_allocated(currcons)) {
/* could this happen? */
@@ -3312,16 +3302,13 @@ static void con_start(struct tty_struct *tty)

static void con_flush_chars(struct tty_struct *tty)
{
- struct vc_data *vc;
+ struct vc_data *vc = tty->driver_data;

if (in_interrupt()) /* from flush_to_ldisc */
return;

- /* if we race with con_close(), vt may be null */
console_lock();
- vc = tty->driver_data;
- if (vc)
- set_cursor(vc);
+ set_cursor(vc);
console_unlock();
}

--
2.43.0