USB: ohci_hcd hang: submit vs. rmmod race
If we do rmmod ohci_hcd while an application is doing something, the
following may happen:
- a control URB completes (in finish_urb) and the ohci's endpoint is
set into ED_UNLINK in ed_deschedule
- same URB is (re)submitted because of the open/close loop or other
such application behaviour
- rmmod sets the state to HC_STATE_QUESCING
- finish_unlinks happens at next SOF; normally it would set ed into
ED_IDLE and immediately call ed_schedule (since URB had extra TDs
queued), which sets it into ED_OPER. But the check in ed_schedule
makes it fail with -EAGAIN (which is ignored)
- from now on we have a dead URB stuck; it cannot even be unlinked
because the ed status is not ED_OPER, and thus start_ed_unlink is
not invoked.
This patch removes the check. In 2.6.25, all callers check for
__ACTIVE bit before invoking ed_schedule, which is more appropriate.
Alan Stern and David Brownell approved of this (cautiously).
Signed-off-by: Pete Zaitcev <zaitcev@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
1 file changed