Re: [Xen-devel] [PATCH] [PVOPS] fix gntdev on PAE

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 06/01/2010 09:36 AM, Stefano Stabellini wrote:
>>> Performances shouldn't matter in this case.
>>> Something like this:
>>>   
>>>       
>> The problem is that the rcu lock disables preemption, so anything inside
>> it must be non-scheduling.  So it would need to be a spinlock type
>> thing, I think.
>>     
> right, in fact rwlock is a rw spinlock if I am not mistaken
>   

Ah, yes.  The problem with just making it a spinlock is that other parts
of the code do copy_from_user while holding it, so they would need to be
restructured to avoid that.

Also, rwlock is (almost?) never useful compared to a plain spinlock.

    J

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