Rogue usb sticks can cause endless port connect change events due to unstable electric connection between usb chip and the port. Port connect change will cause device enumeration for the new device connection and new device processing is done with the usb hub mutex acquired. This can cause very short time gap between unlock/lock of hub device mutex. So if some thread is running at low priority than hub_thread, it can face hub device mutex starvation. This commit introduces a sleep of 25ms after the hub device mutex is unlocked in hub_events so that if hub_thread is stuck in a endless loop, all other threads will get fair amount of chance to acquire the usb hub mutex. Signed-off-by: Sanjeev Chugh <sanjeev_chugh@xxxxxxxxxx> --- drivers/usb/core/hub.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 00070a8..0be2acc 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -5763,6 +5763,17 @@ static void hub_event(struct work_struct *work) out_hdev_lock: usb_unlock_device(hdev); + /* + * Rogue usb sticks can cause endless device connection + * events due to unstable electric connection. This + * can cause very short time gap between unlock/lock + * of hub device mutex thus causing mutex starvation + * for some other lower priority thread. Thus sleep + * would give fair chance to all other threads to + * acquire the usb hub mutex. + */ + msleep(25); + /* Balance the stuff in kick_hub_wq() and allow autosuspend */ usb_autopm_put_interface(intf); kref_put(&hub->kref, hub_release); -- 2.7.4
