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From: Linhaifeng <haifeng.lin@huawei.com>
To: Luke Gorrie <luke@snabb.co>
Cc: "dev@dpdk.org" <dev@dpdk.org>, "Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [dpdk-dev] [PATCH] vhost: flush used->idx update before reading avail->flags
Date: Tue, 9 Jun 2015 15:04:02 +0800	[thread overview]
Message-ID: <55768FE2.5060505@huawei.com> (raw)
In-Reply-To: <CAA2XHbef=TBAoAwNaAuVOAtHBqiQg2rD1-ExAYkHJ4pLsozJ3Q@mail.gmail.com>



On 2015/4/24 15:27, Luke Gorrie wrote:
> On 24 April 2015 at 03:01, Linhaifeng <haifeng.lin@huawei.com> wrote:
> 
>> If not add memory fence what would happen? Packets loss or interrupt
>> loss?How to test it ?
>>
> 
> You should be able to test it like this:
> 
> 1. Boot two Linux kernel (e.g. 3.13) guests.
> 2. Connect them via vhost switch.
> 3. Run continuous traffic between them (e.g. iperf).
> 
> I would expect that within a reasonable timeframe (< 1 hour) one of the
> guests' network interfaces will hang indefinitely due to a missed interrupt.
> 
> You won't be able to reproduce this using DPDK guests because they are not
> using the same interrupt suppression method.
> 
> This is a serious real-world problem. I wouldn't deploy the vhost
> implementation without this fix.
> 
> Cheers,
> -Luke
> 

I think this patch can't resole this problem. On the other hand we still would miss interrupt.

After add rte_mb() function the we want the case is :
1.write used->idx. ring is full or empty.
2.virtio_net open interrupt.
3.read avail->flags.

but this case(miss interrupt) would happen too:
1.write used->idx. ring is full or empty.
2.read avail->flags.
3.virtio_net open interrupt.

  reply	other threads:[~2015-06-09  7:04 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-04-22 16:33 Huawei Xie
2015-04-23 13:57 ` Luke Gorrie
2015-04-24  1:01 ` Linhaifeng
2015-04-24  2:40   ` Xie, Huawei
2015-04-24  7:27   ` Luke Gorrie
2015-06-09  7:04     ` Linhaifeng [this message]
2015-06-09  7:45       ` Luke Gorrie
2015-06-09  8:46       ` Michael S. Tsirkin
2015-06-09 13:34         ` Xie, Huawei
2015-06-10  2:36           ` Linhaifeng
2015-06-10  8:30         ` Luke Gorrie
2015-06-11  0:50           ` Linhaifeng
2015-04-29 11:11 ` [dpdk-dev] [PATCH v2] " Huawei Xie
2015-05-13 10:46   ` Thomas Monjalon
2015-05-15 13:43     ` Nikita Kalyazin
2015-05-15 15:23       ` Michael S. Tsirkin
2015-05-18  6:18         ` Nikita Kalyazin

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