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SubjectRe: Kernel bug: bluetooth meets TTY layer
Hi Arjan,

I've not been able to find this file, "drivers/bluetooth/hci_tty.c", but
anyway, This seems to be what happens: Hci_uart_close() flushes using
hci_uart_flush(). Subsequently, in hci_dev_do_close(), (one step in
hci_unregister_dev()), hci_uart_flush() is called again. The comment in
uart_flush_buffer(), relating to the WARN_ON(), indicates you can't
flush after the port is closed; which sounds reasonable. I think
hci_uart_close() should set hdev->flush to NULL before returning.
Hci_dev_do_close() does check for this. The code path is rather
involved and I'm not entirely clear of all steps, but I think that's
what should be done.

Patch for stupidly obsolete kernel attached.

--- hci_ldisc.c 2007-09-11 02:54:02.000000000 +0930
+++ 2007-12-21 06:03:11.000000000 +1030
@@ -203,16 +203,17 @@
static int hci_uart_close(struct hci_dev *hdev)
BT_DBG("hdev %p", hdev);

if (!test_and_clear_bit(HCI_RUNNING, &hdev->flags))
return 0;

+ hdev->flush = NULL;
return 0;

/* Send frames from HCI layer */
static int hci_uart_send_frame(struct sk_buff *skb)
struct hci_dev* hdev = (struct hci_dev *) skb->dev;
struct tty_struct *tty;
 \ /
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