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Subject[PATCH 7/7] kvm,mips: Fix potential swait_active() races
Date
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>
---
arch/mips/kvm/mips.c | 4 ++--
1 file 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);
}

--
2.12.0
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