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SubjectRe: [PATCH 7/7] kvm,mips: Fix potential swait_active() races
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On 13/09/2017 22:08, Davidlohr Bueso wrote:
> 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);
> }
>
>

has_sleeper*s*. Can fix when committing.

Paolo

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