[src/trunk]: src/sys/arch/xen/xen hypervisor_set_ipending() should not set th...

[cherry <cherry%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/60b40feb9efa
branches:  trunk
changeset: 782885:60b40feb9efa
user:      cherry <cherry%NetBSD.org@localhost>
date:      Sun Nov 25 07:48:46 2012 +0000

description:
hypervisor_set_ipending() should not set the pending flag across cpus. The reason for this is that the pending flag update is not atomic, or protected by a lock. Since its current (mis)use in 
evtchn_do_event() across cpus is to notify the remote cpu of an interrupt, we use hypervisor_send_event() instead, to trigger an event on the remote cpu, which in turn invokes evtchn_do_event() on 
that cpu and DTRT on it.

On the local cpu, we protect hypervisor_set_ipending() from re-entry via cli(). Remove a redundant and unprotected call to hypervisor_set_ipending().

Thanks to jym@ for spotting this discrepancy while reviewing a related patch.

See: http://mail-index.netbsd.org/tech-kern/2012/11/12/msg014374.html

diffstat:

 sys/arch/xen/xen/evtchn.c |  9 +++------
 1 files changed, 3 insertions(+), 6 deletions(-)

diffs (35 lines):

diff -r 9dce8425b191 -r 60b40feb9efa sys/arch/xen/xen/evtchn.c
--- a/sys/arch/xen/xen/evtchn.c Sun Nov 25 04:06:59 2012 +0000
+++ b/sys/arch/xen/xen/evtchn.c Sun Nov 25 07:48:46 2012 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: evtchn.c,v 1.62 2012/02/12 14:24:08 jym Exp $  */
+/*     $NetBSD: evtchn.c,v 1.63 2012/11/25 07:48:46 cherry Exp $       */
 
 /*
  * Copyright (c) 2006 Manuel Bouyer.
@@ -54,7 +54,7 @@
 
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: evtchn.c,v 1.62 2012/02/12 14:24:08 jym Exp $");
+__KERNEL_RCSID(0, "$NetBSD: evtchn.c,v 1.63 2012/11/25 07:48:46 cherry Exp $");
 
 #include "opt_xen.h"
 #include "isa.h"
@@ -298,15 +298,12 @@
        ih = evtsource[evtch]->ev_handlers;
        while (ih != NULL) {
                if (ih->ih_cpu != ci) {
-                       hypervisor_set_ipending(ih->ih_cpu, 1 << ih->ih_level,
-                           evtch >> LONG_SHIFT, evtch & LONG_MASK);
+                       hypervisor_send_event(ih->ih_cpu, evtch);
                        iplmask &= ~IUNMASK(ci, ih->ih_level);
                        ih = ih->ih_evt_next;
                        continue;
                }
                if (ih->ih_level <= ilevel) {
-                       hypervisor_set_ipending(ih->ih_cpu, iplmask,
-                           evtch >> LONG_SHIFT, evtch & LONG_MASK);
 #ifdef IRQ_DEBUG
                if (evtch == IRQ_DEBUG)
                    printf("ih->ih_level %d <= ilevel %d\n", ih->ih_level, ilevel);