On Thu, Sep 20, 2012 at 08:16:08AM +0800, Fengguang Wu wrote:
> Hi Michael,
>
> FYI, there are new compile warnings show up in
>
> tree: git://git.kernel.org/pub/scm/virt/kvm/kvm.git queue
> head: 879238fecc051d95037ae76332916209a7770709
> commit: 9fc77441e5e1bf80b794cc546d2243ee9f4afb75 [41/42] KVM: make processes waiting on vcpu mutex killable
> config: s390-defconfig
>
> All error/warnings:
>
> arch/s390/kvm/interrupt.c: In function 'kvm_s390_handle_wait':
> arch/s390/kvm/interrupt.c:428:12: warning: ignoring return value of 'vcpu_load', declared with attribute warn_unused_result [-Wunused-result]
>
> vim +428 arch/s390/kvm/interrupt.c
> 418 add_wait_queue(&vcpu->arch.local_int.wq, &wait);
> 419 while (list_empty(&vcpu->arch.local_int.list) &&
> 420 list_empty(&vcpu->arch.local_int.float_int->list) &&
> 421 (!vcpu->arch.local_int.timer_due) &&
> 422 !signal_pending(current)) {
> 423 set_current_state(TASK_INTERRUPTIBLE);
> 424 spin_unlock_bh(&vcpu->arch.local_int.lock);
> 425 spin_unlock(&vcpu->arch.local_int.float_int->lock);
> 426 vcpu_put(vcpu);
> 427 schedule();
> > 428 vcpu_load(vcpu);
> 429 spin_lock(&vcpu->arch.local_int.float_int->lock);
> 430 spin_lock_bh(&vcpu->arch.local_int.lock);
> 431 }
> 432 __unset_cpu_idle(vcpu);
> 433 __set_current_state(TASK_RUNNING);
> 434 remove_wait_queue(&vcpu->arch.local_int.wq, &wait);
> 435 spin_unlock_bh(&vcpu->arch.local_int.lock);
> 436 spin_unlock(&vcpu->arch.local_int.float_int->lock);
> 437 hrtimer_try_to_cancel(&vcpu->arch.ckc_timer);
> 438 return 0;
Thanks for the report. This is because vcpu_load can now fail if task
is being killed. I'm guessing the following is the right fix but have
no way to tell. Warning: completely untested.
--->
kvm/arm: handle vcpu_load failure gracefully
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
--
diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
index b7bc1aa..5aedf25 100644
--- a/arch/s390/kvm/interrupt.c
+++ b/arch/s390/kvm/interrupt.c
@@ -362,6 +362,7 @@ int kvm_s390_handle_wait(struct kvm_vcpu *vcpu)
{
u64 now, sltime;
DECLARE_WAITQUEUE(wait, current);
+ int ret;
vcpu->stat.exit_wait_state++;
if (kvm_cpu_has_interrupt(vcpu))
@@ -407,7 +408,9 @@ no_timer:
spin_unlock(&vcpu->arch.local_int.float_int->lock);
vcpu_put(vcpu);
schedule();
- vcpu_load(vcpu);
+ ret = vcpu_load(vcpu);
+ if (ret)
+ goto cancel;
spin_lock(&vcpu->arch.local_int.float_int->lock);
spin_lock_bh(&vcpu->arch.local_int.lock);
}
@@ -416,6 +419,7 @@ no_timer:
remove_wait_queue(&vcpu->arch.local_int.wq, &wait);
spin_unlock_bh(&vcpu->arch.local_int.lock);
spin_unlock(&vcpu->arch.local_int.float_int->lock);
+cancel:
hrtimer_try_to_cancel(&vcpu->arch.ckc_timer);
return 0;
}
> ---
> 0-DAY kernel build testing backend Open Source Technology Centre
> Fengguang Wu, Yuanhan Liu Intel Corporation
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