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Date: Thu, 28 Nov 2013 13:33:17 +0200
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Subject: Re: [Qemu-devel] [RFC] create a single workqueue for each vm to
 update vm irq routing table
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To: Paolo Bonzini <pbonzini@redhat.com>, Gleb Natapov <gleb@minantech.com>
Cc: "Huangweidong (C)" <weidong.huang@huawei.com>, KVM <kvm@vger.kernel.org>, Gleb Natapov <gleb@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>, "Zhanghaoyu (A)" <haoyu.zhang@huawei.com>, Luonengjun <luonengjun@huawei.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, Zanghongyong <zanghongyong@huawei.com>, Avi Kivity <avi.kivity@gmail.com>, "Jinxin (F)" <jinxin712@huawei.com>

On 11/28/2013 01:31 PM, Paolo Bonzini wrote:
> Il 28/11/2013 12:23, Gleb Natapov ha scritto:
>>>>>> Unless what ? :) Unless reader is scheduled out?
>>>> Yes.  Or unless my brain is scheduled out in the middle of a sentence.
>>>>
>> So we will have to disable preemption in a reader to prevent big latencies for
>> a writer, no?
> I don't think that's necessary.  The writer itself could also be
> scheduled out, and the reader critical sections are really small.  Let's
> wait for Zhang to try SRCU and report back.
>

I think readers have preemption disabled already in that context (irqfd 
writes).