linux-kernel - Re: [PATCH] KVM: async_pf: Fix rcu_irq

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Date:   Wed, 7 Jun 2017 16:24:51 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH] KVM: async_pf: Fix rcu_irq_enter/exit() usage



On 07/06/2017 16:10, Wanpeng Li wrote:
> 2017-06-07 21:05 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
>>
>>
>> On 07/06/2017 14:04, Wanpeng Li wrote:
>>> From: Wanpeng Li <wanpeng.li@...mail.com>
>>>
>>> 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.

So it's just code cleanup?

Paolo