Re: [PATCH] KVM: async_pf: Fix rcu_irq_enter/exit() usage

[Wanpeng Li]

2017-06-07 21:05 GMT+08:00 Paolo Bonzini <pbonzini@xxxxxxxxxx>:
>
>
> On 07/06/2017 14:04, Wanpeng Li wrote:
>> From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
>>
>> Commit 9b132fbe5419 (Add rcu user eqs exception hooks for async page fault)
>> adds rcu_irq_enter/exit() to kvm_async_pf_task_wait() to exit cpu idle eqs
>> when needed, to protect the code that needs use rcu. There is no need to call
>> this pairs if async page fault is not triggered from idle task.
>>
>> This patch fixes it by rcu irq exit if it is not triggered from idle task to
>> avoid rcu hang after schedule() in the for loop.
>
> How does the bug manifest?

Just by codes review.

Regards,
Wanpeng Li