Re: [boost] Lock-free atomic_shared_ptr<T>?

From: Andrey Tcherepanov (moyt63c02_at_[hidden])
Date: 2008-01-18 17:57:42

Well, according to  
http://en.wikipedia.org/wiki/X86-64#Virtual_address_space_details
it might be dangerous to rely on the fact that top 16 bits are not  
currently used.

On Fri, 18 Jan 2008 15:03:21 -0700, Tim Blechmann <tim_at_[hidden]> wrote:

> On Fri, 18 Jan 2008 12:43:39 -0800, Cory Nelson wrote:
>
>> On Jan 18, 2008 9:56 AM, Jeffrey Yasskin <jyasskin_at_[hidden]> wrote:
>>> using shared_ptr<T> as a value type. The implementation I'm thinking of
>>> uses hazard pointers
>>> (http://erdani.org/publications/cuj-2004-12.pdf) and double-wide-cas
>>> (cmpxchg16b on x86-64). So I have three questions for this list:
>>
>> Athlon 64s (pre-dual core) do not have cmpxchg16b - how do you plan to
>> get around that?
>
> iirc, the x86_64 doesn't actually use a 64-bit virtual address space, but
> only 48-bit ... the remaining 16 bit could be used to store the tag ...
>
> best, tim
>