assembly-language mutex support

assembly-language mutex support

[Bart Heinsius]

Hi,

I read some time ago that Xen does not have assembly-language mutex support.
Is this still the case in Xen 3.2?

best regards,
Bart.

Re: assembly-language mutex support

[Keir Fraser]

What does that even mean?

 -- Keir


On 4/4/08 21:45, "Bart Heinsius" <bheinsius@gmail.com> wrote:

> Hi,
> 
> I read some time ago that Xen does not have assembly-language mutex support.
> Is this still the case in Xen 3.2?
> 
> best regards,
> Bart.
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel

Re: assembly-language mutex support

[Bart Heinsius]

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Re: assembly-language mutex support

[Keir Fraser]

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Ah, I think this is related to difficulties supporting Œnegative segment
accesses¹. This means we have to rebuild glibc and we lose some NPTL
functionality in doing that.

However, this problem is not present if you run a 64-bit hypervisor. You can
run 64-bit or 32-bit (PAE) Linux guests on the 64-bit hypervisor with no
limitations (even as domain 0) and the Œnegative segment access¹ problem
goes away.

You should try that out! The only tricky point may be if the distro you use
has deliberately picked different glibc when running a 32-bit Xen version of
Linux, despite the fact you are running on 64-bit hypervisor. In  that case
you might have to tweak a ld.so config file to stop searching for nosegneg
libraries.

But short answer is: use a 64-bit hypervisor and it should all work fine.

 -- Keir

On 4/4/08 22:30, "Bart Heinsius" <bheinsius@gmail.com> wrote:

> I don't know what it means exactly, except that it hear it can cause problems
> for BDB.
> I want to run a production Zimbra instance in a Xen vm and certain people at
> Zimbra advice me to not do that unless it has assembly-language mutex support,
> since BDB uses assembly level mutex locks by default.
> I was pointed to:
> https://bugzilla.redhat.com/show_bug.cgi?id=91933
> http://www.openldap.org/lists/openldap-software/200603/msg00214.html
> 
> and
> http://www.zimbra.com/forums/installation/14121-virtualization-zimbra.html
> 
> -- Bart
> 
> Keir Fraser wrote:
>>  
>> What does that even mean?
>> 
>>  -- Keir
>> 
>> 
>> On 4/4/08 21:45, "Bart Heinsius" <bheinsius@gmail.com>
>> <mailto:bheinsius@gmail.com>  wrote:
>> 
>>   
>>  
>>>  
>>> Hi,
>>> 
>>> I read some time ago that Xen does not have assembly-language mutex support.
>>> Is this still the case in Xen 3.2?
>>> 
>>> best regards,
>>> Bart.
>>> 
>>> 
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@lists.xensource.com
>>> http://lists.xensource.com/xen-devel
>>>     
>>>  
>>  
>> 
>> 
>>   
> 
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel



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