Messages in this thread Patch in this message | | | Date | Wed, 05 Jan 2011 15:00:49 -0800 | From | Greg KH <> | Subject | [31/49] hvc_console: Fix race between hvc_close and hvc_remove, again |
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2.6.32-longterm review patch. If anyone has any objections, please let us know.
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From: Anton Blanchard <anton@samba.org>
commit 320718ee074acce5ffced6506cb51af1388942aa upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
--- drivers/char/hvc_console.c | 4 ---- 1 file changed, 4 deletions(-)
--- a/drivers/char/hvc_console.c +++ b/drivers/char/hvc_console.c @@ -367,16 +367,12 @@ static void hvc_close(struct tty_struct 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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