Re: Synchronizing if_xennet_xenbus detach with event-handling

[Taylor R Campbell <campbell+netbsd-tech-kern%mumble.net@localhost>]

   Date: Tue, 9 Feb 2016 08:51:43 +0100
   From: Manuel Bouyer <bouyer%antioche.eu.org@localhost>

   On Mon, Feb 08, 2016 at 04:34:20PM -0800, Rohan Desai wrote:
   > BTW,
   > in my crash detach is waiting on a cv in softint_disestablish()

   If softint_disestablish() can sleep that may be more problematic.
   In this case event_remove_handler() should be called before
   softint_disestablish().

softint_disestablish may sleep in order to wait for all softints still
executing on other CPUs to complete.  The caller must guarantee that
no new ones will be scheduled before calling softint_disestablish, but
there may be ones that were already scheduled but have not yet
completed.