Am 02.04.2012 11:03, schrieb Andrei Emeltchenko: > Hi guys, > > On Mon, Apr 02, 2012 at 10:44:43AM +0200, David Herrmann wrote: >> Hi Andrei and Alexander >> >> On Mon, Apr 2, 2012 at 10:29 AM, Alexander Holler <holler@xxxxxxxxxxxxx> wrote: >>> Am 02.04.2012 08:55, schrieb Andrei Emeltchenko: >>>> 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? >>> >>> By reading the source, printk and suffering through the deadlock. It's >>> especially painfull when using a bt-keyboard and systemd, because >>> systemd tries 4 times (~ some minutes) to kill bluetoothd before it >>> marks the service as failed and finally continues to shut down. >> >> hci_conn_timeout does lock the device. See the source. But the problem > > I think you need to check commit e72acc13c770a82b4ce4a07e9716f29320eae0f8 > > commit e72acc13c770a82b4ce4a07e9716f29320eae0f8 > Author: Andre Guedes <andre.guedes@xxxxxxxxxxxxx> > Date: Fri Jan 27 19:42:03 2012 -0300 > > Bluetooth: Remove unneeded locking > > We don't need locking hdev in hci_conn_timeout() since it doesn't > access any hdev's shared resources, it basically queues HCI commands. So if the locks in hci_conn_timeout() aren't needed, your commit which removes them should go to the stable tree because it fixes a painful deadlock. Regards, Alexander -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
