kvm,mips: Fix potential swait_active() races

For example, the following could occur, making us miss a wakeup:

CPU0					CPU1
kvm_vcpu_block				kvm_mips_comparecount_func
					  [L] swait_active(&vcpu->wq)
  [S] prepare_to_swait(&vcpu->wq)
  [L] if (!kvm_vcpu_has_pending_timer(vcpu))
         schedule()                       [S] queue_timer_int(vcpu)

Ensure that the swait_active() check is not hoisted over the interrupt.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index bce2a6431430..d535edc01434 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -514,7 +514,7 @@ int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu,
 
         dvcpu->arch.wait = 0;
 
-        if (swait_active(&dvcpu->wq))
+        if (swq_has_sleeper(&dvcpu->wq))
                 swake_up(&dvcpu->wq);
 
         return 0;
@@ -1179,7 +1179,7 @@ static void kvm_mips_comparecount_func(unsigned long data)
         kvm_mips_callbacks->queue_timer_int(vcpu);
 
         vcpu->arch.wait = 0;
-        if (swait_active(&vcpu->wq))
+        if (swq_has_sleeper(&vcpu->wq))
                 swake_up(&vcpu->wq);
 }