[PATCH 2/5] tty: Push the lock down further into the ldisc code

Alan Cox
2009-11-18T14:42:28Z

drivers/char/tty_io.c | 2 --
drivers/char/tty_ldisc.c | 12 +++++++++---
2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 05e94a2..a1b1ff6 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1347,9 +1347,7 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
* If we fail here just call release_tty to clean up. No need
* to decrement the use counts, as release_tty doesn't care.
*/
- lock_kernel();
retval = tty_ldisc_setup(tty, tty->link);
- unlock_kernel();
if (retval)
goto release_mem_out;
return tty;
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index d914e77..3f653f7 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -445,8 +445,14 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
{
WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
- if (ld->ops->open)
- return ld->ops->open(tty);
+ if (ld->ops->open) {
+ int ret;
+ /* BKL here locks versus a hangup event */
+ lock_kernel();
+ ret = ld->ops->open(tty);
+ unlock_kernel();
+ return ret;
+ }
return 0;
}

@@ -566,6 +572,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
return 0;
}

+ unlock_kernel();
/*
* Problem: What do we do if this blocks ?
* We could deadlock here
@@ -573,7 +580,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

tty_wait_until_sent(tty, 0);

- unlock_kernel();
mutex_lock(&tty->ldisc_mutex);

/*