On Tue, 2013-01-15 at 20:27 +0000, Karl Relton wrote: > > The end result (for the user) is that even when the bluetooth > > mouse/keyboard is re-added, Xorg ignores it - thinking it is some > hoax > > duplicate device. The keyboard/mouse is then non-operational. > > > > Instrumenting the code suggests that the issue arises in a race > between: > > hidp_session() in bluetooth/hidp/core.c > > and > > hci_unregister_dev() in bluetooth/hci_core.c > > > Basically hci_unregister_dev() does a hci_dev_do_close() which in turn > shuts down the hidp connection. This causes hidp_session() running in > another thread to go into its cleanup phase, which is where the input > children devices are unregistered. > > HOWEVER: > 1) For some reason input_unregister_device() seems to stall some 3-5 > seconds on my system before removing the input device > 2) In parallel hci_unregister_dev() ploughs on, and progresses to > remove > its hdev (hci<n> device) regardless, without waiting for > hidp_session() > to complete. > > I can't figure out why there is such a delay for > input_unregister_device(). The power_supply system seems to be triggering a lookup of battery 'capacity' in the input device. This calls into the driver, which deep down invokes more code in the 'hidp' module: hidp_get_raw_report() This function tries to communicate with the bluetooth device (keyboard in my case), but because the device is being 'torn down' such communication fails. Accordingly hidp_get_raw_report has a 5 second timeout ... so this function stalls for 5 seconds until that timeout occurs. I would guess that for some reason, removing the 'hid' or associated 'input' device is leading to the power_supply code wanting to lookup the battery capacity which introduces a 5 second wait. This would delay hidp_session by 5 seconds ... in the mean time allowing hci_unregister_dev() to win the race and hence the hci device is removed before the input & hid devices. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
