linux-kernel - [PATCH 5/7] kvm: Serialize wq active checks in kvm_vcpu_wake

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Message-Id: <20170913200824.28067-6-dave@stgolabs.net>
Date:   Wed, 13 Sep 2017 13:08:22 -0700
From:   Davidlohr Bueso <dave@...olabs.net>
To:     mingo@...nel.org, peterz@...radead.org, pbonzini@...hat.com
Cc:     npiggin@...il.com, paulmck@...ux.vnet.ibm.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, dave@...olabs.net,
        Davidlohr Bueso <dbueso@...e.de>
Subject: [PATCH 5/7] 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 6ed1c2021198..c41d903c5783 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2186,7 +2186,7 @@ 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