Prev: workqueue: concurrency managed workqueue, take#5
Next: [PATCH 1/6] tracing: Update the comm field in the right variable in update_max_tr
From: John Kacur on 14 Jun 2010 18:30
From: Anton Blanchard <anton(a)samba.org>

I don't claim to understand the tty layer, but it seems like hvc_open and
hvc_close should be balanced in their kref reference counting.

Right now we get a kref every call to hvc_open:

if (hp->count++ > 0) {
tty_kref_get(tty); <----- here
spin_unlock_irqrestore(&hp->lock, flags);
hvc_kick();
return 0;
} /* else count == 0 */

tty->driver_data = hp;

hp->tty = tty_kref_get(tty); <------ or here if hp->count was 0

But hvc_close has:

tty_kref_get(tty);

if (--hp->count == 0) {
....
/* Put the ref obtained in hvc_open() */
tty_kref_put(tty);
....
}

tty_kref_put(tty);

Since the outside kref get/put balance we only do a single kref_put when
count reaches 0.

The patch below changes things to call tty_kref_put once for every
hvc_close call, and with that my machine boots fine.

Signed-off-by: Anton Blanchard <anton(a)samba.org>
Acked-by: Amit Shah <amit.shah(a)redhat.com>
Signed-off-by: Rusty Russell <rusty(a)rustcorp.com.au>
Upstream-commit: 320718ee074acce5ffced6506cb51af1388942aa
Signed-off-by: John Kacur <jkacur(a)redhat.com>
---
drivers/char/hvc_console.c | 4 ----
1 files changed, 0 insertions(+), 4 deletions(-)

diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index da70f68..2898084 100644
--- a/drivers/char/hvc_console.c
+++ b/drivers/char/hvc_console.c
@@ -367,16 +367,12 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
hp = tty->driver_data;

spin_lock_irqsave(&hp->lock, flags);
- tty_kref_get(tty);

if (--hp->count == 0) {
/* We are done with the tty pointer now. */
hp->tty = NULL;
spin_unlock_irqrestore(&hp->lock, flags);

- /* Put the ref obtained in hvc_open() */
- tty_kref_put(tty);
-
if (hp->ops->notifier_del)
hp->ops->notifier_del(hp, hp->data);

--
1.6.6.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo(a)vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
 | 
Pages: 1
Prev: workqueue: concurrency managed workqueue, take#5
Next: [PATCH 1/6] tracing: Update the comm field in the right variable in update_max_tr