commit 00e36c829fe87a3d285d7a774eb8a1ca8797d0c0
author Hans de Goede <hdegoede@redhat.com> Tue Jun 07 12:12:38 2016 +0200
committer Nathan Hjelm <hjelmn@me.com> Wed Aug 17 12:52:40 2016 -0600
tree 47ee07189a4136faae9a2e91590f922bf29c5fa5
parent 9542c38cf2cbd911bd7e3ec161e564b3ae63d4fe

linux_usbfs: Deal with receiving POLLERR before all transfers have completed

The linux kernel will set its internal device state to USB_STATE_NOTATTACHED
as soon as it detects the disconnect, and then start a worker thread to
deal with the actual disconnection, kill outstanding urbs, etc.

The usbfs poll implementation will return POLL_ERR as soon as
ps->dev->state == USB_STATE_NOTATTACHED. The kernel will not wakeup
the poll until it is done with processing the disconnection. But if
we happen to call poll() between the state change and the disconnection
being fully processed, we may not be able to reap all outstanding transfers,
even on kernels with the USBFS_CAP_REAP_AFTER_DISCONNECT capability.

This commit deals with this by trying to reap as many transfers as possible
on disconnect on USBFS_CAP_REAP_AFTER_DISCONNECT capable kernels and then
calling usbi_handle_disconnect(handle) to deal with any remaining ones.
On USBFS_CAP_REAP_AFTER_DISCONNECT capable kernels this will be a no-op
unless we hit the race.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>