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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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