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Re: [Xen-users] [Xen-devel] vif-bridge errors when creating and destroying dozens of VMs simultaneously


Patch works as expected, no failures on create and no stale iptables
rules after running under the same load that was producing the errors

Ubuntu 16.04
Linux 3.13.0-83-generic
iptables v1.6.0
Xen 4.6 5 from distro packages



On Wed, May 17, 2017 at 7:44 AM, George Dunlap <george.dunlap@xxxxxxxxxx> wrote:
> On Wed, May 17, 2017 at 1:46 PM, George Dunlap <george.dunlap@xxxxxxxxxx> 
> wrote:
>> On 17/05/17 13:43, Ian Jackson wrote:
>>> George Dunlap writes ("Re: [Xen-devel] [Xen-users] vif-bridge errors when 
>>> creating and destroying dozens of VMs simultaneously"):
>>>> So we have three options:
>>> ...
>>>> 3. Try to check to see if the version of iptables we have supports -w,
>>>> and use it if available.  This should also work on all systems, but
>>>> introduces a bit of complication.  It also doesn't allow us to
>>>> reliably use a timeout.
>>> I think this is best.  Eventually we can get rid of the check for -w.
>>> I think a timeout in this context is not very helpful.
>>> Also, a loop, on a busy system, might need to have many attempts,
>>> because it will be polling.
>> FWIW the iptables internal mechanism will try to grab the lock, and if
>> it fails (and -w is set), will call sleep(1) before trying again.  My
>> bash loop would do exactly the same thing.
>> But I agree that if timeouts are not important, doing it via iptables is
>> probably cleaner.  Let me work up a patch.
> Antony,
> Attached is a patch to add the -w option if it's available.  I've
> smoke-tested that it works under normal conditions; but my simplistic
> attempts to get the bug to trigger have failed.  Can you give it a try
> and see if it works?
> Thanks,
>  -George

Antony Saba, awsaba@xxxxxxxxx

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