On 2020-07-11 11:04, Andrew Jones wrote:
We should only check current->sched_info.run_delay once when
updating stolen time. Otherwise there's a chance there could
be a change between checks that we miss (preemption disabling
comes after vcpu request checks).
Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
---
arch/arm64/kvm/pvtime.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kvm/pvtime.c b/arch/arm64/kvm/pvtime.c
index 2b22214909be..db5ef097a166 100644
--- a/arch/arm64/kvm/pvtime.c
+++ b/arch/arm64/kvm/pvtime.c
@@ -13,6 +13,7 @@
void kvm_update_stolen_time(struct kvm_vcpu *vcpu)
{
struct kvm *kvm = vcpu->kvm;
+ u64 last_steal = vcpu->arch.steal.last_steal;
u64 steal;
__le64 steal_le;
u64 offset;
@@ -24,8 +25,8 @@ void kvm_update_stolen_time(struct kvm_vcpu *vcpu)
/* Let's do the local bookkeeping */
steal = vcpu->arch.steal.steal;
- steal += current->sched_info.run_delay - vcpu->arch.steal.last_steal;
vcpu->arch.steal.last_steal = current->sched_info.run_delay;
+ steal += vcpu->arch.steal.last_steal - last_steal;
vcpu->arch.steal.steal = steal;
steal_le = cpu_to_le64(steal);
Unless you read current->sched_info.run_delay using READ_ONCE,
there is no guarantee that this will do what you want. The
compiler is free to rejig this anyway it wants.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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