[PATCH 3/6] kvm,lapic: Justify use of swait_activate()

[Davidlohr Bueso]

A comment might serve future readers.

Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
---
 arch/x86/kvm/lapic.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 589dcc117086..fb8be28c7093 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1326,6 +1326,12 @@ static void apic_timer_expired(struct kvm_lapic *apic)
 	atomic_inc(&apic->lapic_timer.pending);
 	kvm_set_pending_timer(vcpu);
 
+	/*
+	 * The above kvm_set_pending_timer implies a wmb
+	 * which pairs with the swaiter side. Either way,
+	 * the atomic_inc() is also serialized so using
+	 * swait_active() is safe.
+	 */
 	if (swait_active(q))
 		swake_up(q);
 
-- 
2.12.0