[PATCH] kvm: fix crash on irqfd deassign

["Michael S. Tsirkin" <mst@redhat.com>]

irqfd in kvm used flush_work incorrectly:
it assumed that work scheduled previously can't run
after flush_work, but since kvm uses a non-reentrant
workqueue (by means of schedule_work)
we need flush_work_sync to get that guarantee.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reported-by: Jean-Philippe Menil <jean-philippe.menil@univ-nantes.fr>
Tested-by: Jean-Philippe Menil <jean-philippe.menil@univ-nantes.fr>
---

Note: this is needed for kernel 2.6.39 and earlier.

 virt/kvm/eventfd.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/virt/kvm/eventfd.c b/virt/kvm/eventfd.c
index 2ca4535..cdf51c9 100644
--- a/virt/kvm/eventfd.c
+++ b/virt/kvm/eventfd.c
@@ -90,7 +90,7 @@ irqfd_shutdown(struct work_struct *work)
 	 * We know no new events will be scheduled at this point, so block
 	 * until all previously outstanding events have completed
 	 */
-	flush_work(&irqfd->inject);
+	flush_work_sync(&irqfd->inject);
 
 	/*
 	 * It is now safe to release the object's resources
-- 
1.7.3.2.91.g446ac