From: Davidlohr Bueso <dave@stgolabs.net>
Date: Wed, 13 Sep 2017 20:08:22 +0000 (-0700)
Subject: kvm: Serialize wq active checks in kvm_vcpu_wake_up()
X-Git-Tag: v4.14-rc1~10^2~5
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=5e0018b3e39e9b44dbfb380b83026e55d2f65b91;p=linux.git

kvm: Serialize wq active checks in kvm_vcpu_wake_up()

This is a generic call and can be suceptible to races
in reading the wq task_list while another task is adding
itself to the list. Add a full barrier by using the
swq_has_sleeper() helper.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 2d7df5cc955b..9deb5a245b83 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2187,7 +2187,7 @@ bool kvm_vcpu_wake_up(struct kvm_vcpu *vcpu)
 	struct swait_queue_head *wqp;
 
 	wqp = kvm_arch_vcpu_wq(vcpu);
-	if (swait_active(wqp)) {
+	if (swq_has_sleeper(wqp)) {
 		swake_up(wqp);
 		++vcpu->stat.halt_wakeup;
 		return true;