linux-kernel - [PATCH 5/6] kvm: Serialize wq active checks in kvm_vcpu_wake

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Date:   Tue,  5 Sep 2017 12:00:21 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     mingo@...hat.com, peterz@...radead.org, pbonzini@...hat.com
Cc:     npiggin@...il.com, paulmck@...ux.vnet.ibm.com, dave@...olabs.net,
        linux-kernel@...r.kernel.org, Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH 5/6] 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@...e.de>
---
 virt/kvm/kvm_main.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4d81f6ded88e..4e76e6d15ce0 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2185,7 +2185,7 @@ 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;
-- 
2.12.0