Messages in this thread Patch in this message | | | From | John Kacur <> | Subject | [PATCH 6/6] hvc_console: Fix race between hvc_close and hvc_remove | Date | Tue, 15 Jun 2010 00:21:27 +0200 |
| |
From: Anton Blanchard <anton@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@samba.org> Acked-by: Amit Shah <amit.shah@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Upstream-commit: 320718ee074acce5ffced6506cb51af1388942aa Signed-off-by: John Kacur <jkacur@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
| |