[Xen-changelog] [xen-unstable] Fix SCHEDOP_poll to avoid wakeup-waiting race on interrupt delivery.

[Xen patchbot-unstable <patchbot-unstable@xxxxxxxxxxxxxxxxxxx>]

# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1224178603 -3600
# Node ID dc61548aa4792aa274a207cae27a3d0a8b62bd73
# Parent  bb1a67a7db26d08ab0fe398ac6489c84e7fd660b
Fix SCHEDOP_poll to avoid wakeup-waiting race on interrupt delivery.

Race found by Jan Beulich.

Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
---
 xen/common/schedule.c |    4 ++++
 1 files changed, 4 insertions(+)

diff -r bb1a67a7db26 -r dc61548aa479 xen/common/schedule.c
--- a/xen/common/schedule.c     Thu Oct 16 15:46:04 2008 +0100
+++ b/xen/common/schedule.c     Thu Oct 16 18:36:43 2008 +0100
@@ -455,6 +455,10 @@ static long do_poll(struct sched_poll *s
         goto out;
 #endif
 
+    rc = 0;
+    if ( local_events_need_delivery() )
+        goto out;
+
     for ( i = 0; i < sched_poll->nr_ports; i++ )
     {
         rc = -EFAULT;

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