Re: [Xen-devel] lock in vhpet

[Keir Fraser <keir@xxxxxxx>]

On 18/04/2012 09:29, "Keir Fraser" <keir@xxxxxxx> wrote:

> On 18/04/2012 08:55, "Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx> wrote:
> 
>>> If the HPET accesses are atomic on bare metal, we have to maintain that,
>>> even
>>> if some guests have extra locking themselves. Also, in some cases Xen needs
>>> locking to correctly maintain its own internal state regardless of what an
>>> (untrusted) guest might do. So we cannot just get rid of the vhpet lock
>>> everywhere. It's definitely not correct to do so. Optimising the hpet read
>>> path
>>> however, sounds okay. I agree the lock may not be needed on that specific
>>> path.
>> 
>> You are right.
>> For this case, since the main access of hpet is to read the main counter, so
>> I
>> think the rwlock is a better choice.
> 
> I'll see if I can make a patch...

Please try the attached patch (build tested only).

 -- Keir

>  -- Keir
> 
>

Attachment: 00-hpet-lockfree
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