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SubjectRe: bluetooth: fix deadlock on device reset and power down
Hi Alexander,

On Sat, Mar 31, 2012 at 03:23:38PM +0200, Alexander Holler wrote:
> I've experienced a deadlock on shutdown using kernel 3.3 and tracked
> it down. Because I'm not very familiar with the bluetooth stack I'm
> not sure if the below patch is correct, but it fixed the problem
> here.

Could you please attach deadlock dump?

>
> Commit 09fd0de5bd8f8ef3317e5365f92f1a13dcd89aa9 introduced a deadlock:
>
> bluetoothd calls ioctl HCIDEVDOWN
> hci_sock_ioctl()
> hci_dev_close()
> hci_dev_do_close()
> hci_dev_lock(hdev);
> inquiry_cache_flush();
> hci_conn_hash_flush();
> hci_conn_del()
> cancel_delayed_work_sync()
> hci_conn_timeout()
> hci_dev_lock(hdev); /* DEADLOCK */

I am actually not sure that hci_conn_timeout locks hdev. Why do you think
so?

Best regards
Andrei Emeltchenko

> hci_dev_unlock(hdev);
>
> Signed-off-by: Alexander Holler <holler@ahsoftware.de>
> ---
> net/bluetooth/hci_core.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
> index 5aeb624..3428036 100644
> --- a/net/bluetooth/hci_core.c
> +++ b/net/bluetooth/hci_core.c
> @@ -629,8 +629,8 @@ static int hci_dev_do_close(struct hci_dev *hdev)
>
> hci_dev_lock(hdev);
> inquiry_cache_flush(hdev);
> - hci_conn_hash_flush(hdev);
> hci_dev_unlock(hdev);
> + hci_conn_hash_flush(hdev);
>
> hci_notify(hdev, HCI_DEV_DOWN);
>
> @@ -713,8 +713,8 @@ int hci_dev_reset(__u16 dev)
>
> hci_dev_lock(hdev);
> inquiry_cache_flush(hdev);
> - hci_conn_hash_flush(hdev);
> hci_dev_unlock(hdev);
> + hci_conn_hash_flush(hdev);
>
> if (hdev->flush)
> hdev->flush(hdev);



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