On Mon, 11 Jan 2010, Oliver Neukum wrote: > Am Montag, 11. Januar 2010 20:32:14 schrieb Alan Stern: > > > I still don't understand. First, why would usb_autosuspend_device(), > > usb_autoresume_device(), or usb_try_autosuspend_device() do > > copy_from_user()? As a general rule, they don't have a meaningful user > > context. Second, why would the driver need to take the device lock? > > I don't know, but quoting you (Documentation/usb/power-management.txt): > > If a driver wants to block all suspend/resume calls during some > critical section, the best way is to lock the device and call > usb_autopm_get_interface() (and do the reverse at the end of the > critical section). Holding the device semaphore will block all > external PM calls, and the usb_autopm_get_interface() will prevent any > internal PM calls, even if it fails. (Exercise: Why?) Yes, but doing I/O isn't a critical section. In general a driver shouldn't need to lock its device while doing I/O. The most notable exception is when a reset is needed for error recovery, and we have a special API for that: usb_lock_device_for_reset(). Can you provide a detailed outline of the deadlock scenario you're concerned about? Maybe show how it would affect usb-storage? Alan Stern -- 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
