Hi,
> From: Amit Shah <amit.s...@redhat.com>
>
> commit e74d098c66543d0731de62eb747ccd5b636a6f4c upstream.
>
> Alan pointed out a race in the code where hvc_remove is invoked. The
> recent virtio_console work is the first user of hvc_remove().
I faintly remember this bug caused boot issues and the following patch
must be applied to fix it.
Anton
--
commit 320718ee074acce5ffced6506cb51af1388942aa
Author: Anton Blanchard <an...@samba.org>
Date: Tue Apr 6 21:42:38 2010 +1000
hvc_console: Fix race between hvc_close and hvc_remove
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 <an...@samba.org>
Acked-by: Amit Shah <amit.s...@redhat.com>
Signed-off-by: Rusty Russell <ru...@rustcorp.com.au>
diff --git a/drivers/char/hvc_console.c b/drivers/char/hvc_console.c
index d3890e8..35cca4c 100644
--- a/drivers/char/hvc_console.c
+++ b/drivers/char/hvc_console.c
@@ -368,16 +368,12 @@ 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);
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