The following reply was made to PR port-xen/29999; it has been noted by GNATS.

From: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
To: Manuel Bouyer <bouyer@antioche.lip6.fr>
Cc: YAMAMOTO Takashi <yamt@mwd.biglobe.ne.jp>, gnats-bugs@NetBSD.org,
	port-xen-maintainer@NetBSD.org, gnats-admin@NetBSD.org,
	netbsd-bugs@NetBSD.org
Subject: Re: port-xen/29999: ctrl_if_interrupt IPL problem
Date: Tue, 19 Apr 2005 13:53:34 +0100

 On Tue, Apr 19, 2005 at 02:45:02PM +0200, Manuel Bouyer wrote:
 > On Tue, Apr 19, 2005 at 01:38:10PM +0100, Christian Limpach wrote:
 > > > Will HYPERVISOR_block() return when there is an event pending, even if
 > > > evtchn_upcall_mask is nonzero ?
 > > 
 > > yes, HYPERVISOR_block() will reenable events in a race-free manner, i.e.
 > > you want to call HYPERVISOR_block() with events disabled and it will return
 > > immediately if there are already pending events.
 > 
 > ha, but events will be reenabled (evtchn_upcall_mask will be reset to 0),
 > right ? If so we can't really run in complete polling mode ...
 
 yes.  I think it would work to keep the spl high and then check the
 interrupt line for control messages.
 
     christian